diff --git a/.changeset/mighty-ligers-beam.md b/.changeset/mighty-ligers-beam.md
new file mode 100644
index 000000000..3c3fc74ef
--- /dev/null
+++ b/.changeset/mighty-ligers-beam.md
@@ -0,0 +1,5 @@
+---
+'wmr': patch
+---
+
+Rewrite internal source map handling. This adds full support for source maps during `development` and `production` and ensures that `.map` files are served correctly.
diff --git a/package.json b/package.json
index 506a30833..63bc57c15 100644
--- a/package.json
+++ b/package.json
@@ -16,7 +16,8 @@
 		"demo": "yarn workspace @examples/demo run",
 		"docs": "yarn workspace docs",
 		"iso": "yarn workspace preact-iso",
-		"ci": "yarn wmr build && yarn --check-files && yarn demo build:prod"
+		"ci": "yarn wmr build && yarn --check-files && yarn demo build:prod",
+		"postinstall": "patch-package --exclude 'nothing'"
 	},
 	"eslintConfig": {
 		"extends": [
@@ -91,6 +92,7 @@
 		"eslint-plugin-prettier": "^3.1.4",
 		"husky": "^4.2.5",
 		"lint-staged": "^10.2.11",
+		"patch-package": "^6.4.7",
 		"prettier": "^2.0.5"
 	}
 }
diff --git a/packages/wmr/package.json b/packages/wmr/package.json
index 5167e8cbd..7550ad189 100644
--- a/packages/wmr/package.json
+++ b/packages/wmr/package.json
@@ -82,6 +82,7 @@
 		"semver": "^7.3.2",
 		"simple-code-frame": "^1.1.1",
 		"sirv": "^1.0.6",
+		"sourcemap-codec": "^1.4.8",
 		"stylis": "^4.0.10",
 		"sucrase": "^3.17.0",
 		"tar-stream": "^2.1.3",
diff --git a/packages/wmr/src/lib/acorn-traverse.js b/packages/wmr/src/lib/acorn-traverse.js
index 08b2ec00a..8e18ded57 100644
--- a/packages/wmr/src/lib/acorn-traverse.js
+++ b/packages/wmr/src/lib/acorn-traverse.js
@@ -3,6 +3,7 @@ import * as jsxWalk from 'acorn-jsx-walk';
 import MagicString from 'magic-string';
 import * as astringLib from 'astring';
 import { codeFrame } from './output-utils.js';
+import { posix } from 'path';
 
 /**
  * @fileoverview
@@ -100,7 +101,16 @@ let codeGenerator = {
 	// import(source)
 	ImportExpression(node, state) {
 		state.write('import(');
-		this[node.source.type](node.source, state);
+
+		// TODO: Sometimes this seems to have a source and sometimes
+		// an expression. I don't understand why. The expression seems
+		// to be only set when calling `t.importExpression()`
+		if (node.source) {
+			this[node.source.type](node.source, state);
+		} else {
+			this[node.expression.type](node.expression, state);
+		}
+
 		state.write(')');
 	},
 	JSXFragment(node, state) {
@@ -745,8 +755,10 @@ export function transform(
 	function getSourceMap() {
 		if (!map) {
 			map = out.generateMap({
-				includeContent: false,
-				source: sourceFileName
+				includeContent: true,
+				// Must be set for most source map verifiers to work
+				source: sourceFileName || filename,
+				file: posix.basename(sourceFileName || filename || '')
 			});
 		}
 		return map;
diff --git a/packages/wmr/src/lib/normalize-options.js b/packages/wmr/src/lib/normalize-options.js
index 0f6efe44a..7a840dbe2 100644
--- a/packages/wmr/src/lib/normalize-options.js
+++ b/packages/wmr/src/lib/normalize-options.js
@@ -21,7 +21,6 @@ export async function normalizeOptions(options, mode, configWatchFiles = []) {
 
 	options.root = options.cwd;
 
-	options.sourcemap = false;
 	options.minify = mode === 'build';
 	options.plugins = [];
 	options.output = [];
diff --git a/packages/wmr/src/lib/npm-middleware.js b/packages/wmr/src/lib/npm-middleware.js
index d5724a6ab..d6b4808ac 100644
--- a/packages/wmr/src/lib/npm-middleware.js
+++ b/packages/wmr/src/lib/npm-middleware.js
@@ -142,6 +142,7 @@ async function bundleNpmModule(mod, { source, alias, cwd }) {
 			aliasPlugin({ alias, cwd }),
 			npmProviderPlugin,
 			processGlobalPlugin({
+				sourcemap: false,
 				NODE_ENV: 'development'
 			}),
 			commonjs({
diff --git a/packages/wmr/src/lib/plugins.js b/packages/wmr/src/lib/plugins.js
index 84cb8f862..76cb79d3f 100644
--- a/packages/wmr/src/lib/plugins.js
+++ b/packages/wmr/src/lib/plugins.js
@@ -53,7 +53,7 @@ export function getPlugins(options) {
 			production
 		}),
 		// Transpile import assertion syntax to WMR prefixes
-		importAssertionPlugin(),
+		importAssertionPlugin({ sourcemap }),
 		production &&
 			(dynamicImportVars.default || dynamicImportVars)({
 				include: /\.(m?jsx?|tsx?)$/,
@@ -61,13 +61,14 @@ export function getPlugins(options) {
 			}),
 		production && publicPathPlugin({ publicPath }),
 		sassPlugin({ production, sourcemap, root }),
-		wmrStylesPlugin({ hot: !production, root, production, alias }),
+		wmrStylesPlugin({ hot: !production, root, production, alias, sourcemap }),
 		processGlobalPlugin({
+			sourcemap,
 			env,
 			NODE_ENV: production ? 'production' : 'development'
 		}),
-		htmPlugin({ production }),
-		wmrPlugin({ hot: !production, preact: features.preact }),
+		htmPlugin({ production, sourcemap: options.sourcemap }),
+		wmrPlugin({ hot: !production, preact: features.preact, sourcemap: options.sourcemap }),
 		fastCjsPlugin({
 			// Only transpile CommonJS in node_modules and explicit .cjs files:
 			include: /(^npm\/|[/\\]node_modules[/\\]|\.cjs$)/
diff --git a/packages/wmr/src/lib/rollup-plugin-container.js b/packages/wmr/src/lib/rollup-plugin-container.js
index 16561912b..dcf1e8df8 100644
--- a/packages/wmr/src/lib/rollup-plugin-container.js
+++ b/packages/wmr/src/lib/rollup-plugin-container.js
@@ -3,7 +3,8 @@ import { createHash } from 'crypto';
 import { promises as fs } from 'fs';
 import * as acorn from 'acorn';
 import * as kl from 'kolorist';
-import { debug, formatResolved, formatPath } from './output-utils.js';
+import { debug, formatResolved, formatPath, hasDebugFlag } from './output-utils.js';
+import { mergeSourceMaps } from './sourcemap.js';
 
 // Rollup respects "module", Node 14 doesn't.
 const cjsDefault = m => ('default' in m ? m.default : m);
@@ -45,7 +46,7 @@ function identifierPair(id, importer) {
 
 /**
  * @param {Plugin[]} plugins
- * @param {import('rollup').InputOptions & PluginContainerOptions} [opts]
+ * @param {import('rollup').InputOptions & PluginContainerOptions & {sourcemap?: boolean}} [opts]
  */
 export function createPluginContainer(plugins, opts = {}) {
 	if (!Array.isArray(plugins)) plugins = [plugins];
@@ -279,6 +280,9 @@ export function createPluginContainer(plugins, opts = {}) {
 		 * @param {string} id
 		 */
 		async transform(code, id) {
+			/** @type {import('./sourcemap.js').SourceMap[]} */
+			const sourceMaps = [];
+
 			for (plugin of plugins) {
 				if (!plugin.transform) continue;
 				const result = await plugin.transform.call(ctx, code, id);
@@ -286,12 +290,32 @@ export function createPluginContainer(plugins, opts = {}) {
 
 				logTransform(`${kl.dim(formatPath(id))} [${plugin.name}]`);
 				if (typeof result === 'object') {
+					if (result.map) {
+						// Normalize source map sources URLs for the browser
+						result.map.sources = result.map.sources.map(s => {
+							if (typeof s === 'string') {
+								return `/${posix.normalize(s)}`;
+							} else if (hasDebugFlag()) {
+								logTransform(kl.yellow(`Invalid source map returned by plugin `) + kl.magenta(plugin.name));
+							}
+
+							return s;
+						});
+
+						sourceMaps.push(result.map);
+					} else if (opts.sourcemap && result.code !== code) {
+						logTransform(kl.yellow(`Missing sourcemap result in transform() method of `) + kl.magenta(plugin.name));
+					}
+
 					code = result.code;
 				} else {
+					if (opts.sourcemap && code !== result) {
+						logTransform(kl.yellow(`Missing sourcemap result in transform() method of `) + kl.magenta(plugin.name));
+					}
 					code = result;
 				}
 			}
-			return code;
+			return { code, map: sourceMaps.length ? mergeSourceMaps(sourceMaps) : null };
 		},
 
 		/**
diff --git a/packages/wmr/src/lib/sourcemap.js b/packages/wmr/src/lib/sourcemap.js
new file mode 100644
index 000000000..7d86609b0
--- /dev/null
+++ b/packages/wmr/src/lib/sourcemap.js
@@ -0,0 +1,185 @@
+import { encode, decode } from 'sourcemap-codec';
+
+/**
+ * @typedef {{ version: number, file?: string, sourceRoot?: string, sources: string[], sourcesContent: Array<string | null>, names: string[], mappings: string}} SourceMap
+ */
+
+/**
+ *
+ * @param {SourceMap[]} maps
+ * @param {import('sourcemap-codec').SourceMapMappings[]} parsedMappings
+ * @param {Map<string, { index: number, content: string | null}>} sourcesCache
+ * @param {number} source
+ * @param {number} line
+ * @param {number} column
+ * @returns {{ line: number, column: number, source: number }}
+ */
+function getOriginalPosition(maps, parsedMappings, sourcesCache, source, line, column) {
+	let originalLine = line;
+	let originalColumn = column;
+	let originalSource = source;
+
+	// Traverse maps backwards, but skip last map as that's the
+	// one we requested the position from
+	for (let i = parsedMappings.length - 1; i >= 0; i--) {
+		const map = parsedMappings[i];
+
+		const segments = map[originalLine];
+		if (!segments) break;
+
+		// TODO: Binary search
+		let lastFound;
+		for (let j = 0; j < segments.length; j++) {
+			const segment = segments[j];
+			if (segment[0] === originalColumn) {
+				if (segment.length === 1) {
+					break;
+				}
+
+				const sourceName = maps[i].sources[segment[1]];
+				const mappedName = sourcesCache.get(sourceName);
+				if (!mappedName) {
+					originalSource = 0;
+				} else {
+					originalSource = mappedName.index;
+				}
+
+				originalLine = segment[2];
+				originalColumn = segment[3];
+				break;
+			} else if (segment[0] < originalColumn) {
+				lastFound = segment;
+			}
+		}
+
+		if (lastFound !== undefined) {
+			if (lastFound.length === 1) {
+				break;
+			}
+
+			const sourceName = maps[i].sources[lastFound[1]];
+			const mappedName = sourcesCache.get(sourceName);
+			if (!mappedName) {
+				originalSource = 0;
+			} else {
+				originalSource = mappedName.index;
+			}
+
+			originalLine = lastFound[2];
+			originalColumn = lastFound[3] + (originalColumn - lastFound[3]);
+		}
+	}
+
+	return {
+		line: originalLine,
+		column: originalColumn,
+		source: originalSource
+	};
+}
+
+/**
+ * Combine an array of sourcemaps into one
+ * @param {SourceMap[]} sourceMaps
+ * @returns {SourceMap}
+ */
+export function mergeSourceMaps(sourceMaps) {
+	let file;
+	let sourceRoot;
+
+	/** @type {import('sourcemap-codec').SourceMapMappings[]} */
+	const parsedMappings = [];
+
+	/** @type {Map<string, number>} */
+	const names = new Map();
+
+	/** @type {Map<string, { index: number, content: string | null}>} */
+	const sourcesCache = new Map();
+
+	for (let i = 0; i < sourceMaps.length; i++) {
+		const map = sourceMaps[i];
+
+		if (map.file) {
+			file = map.file;
+		}
+
+		if (map.sourceRoot) {
+			sourceRoot = map.sourceRoot;
+		}
+
+		for (let j = 0; j < map.sources.length; j++) {
+			const source = map.sources[j];
+			if (!sourcesCache.has(source)) {
+				sourcesCache.set(source, { index: sourcesCache.size, content: map.sourcesContent[j] || null });
+			}
+		}
+
+		for (let j = 0; j < map.names.length; j++) {
+			const name = map.names[j];
+			if (!names.has(name)) {
+				names.set(name, names.size - 1);
+			}
+		}
+
+		// Merge mappings
+		parsedMappings.push(decode(map.mappings));
+	}
+
+	const sources = [];
+	const sourcesContent = [];
+	for (const [key, value] of sourcesCache.entries()) {
+		sources.push(key);
+		sourcesContent.push(value.content);
+	}
+
+	/** @type {import('sourcemap-codec').SourceMapMappings} */
+	const outMappings = [];
+	const lastMap = parsedMappings[parsedMappings.length - 1];
+
+	// Loop over the mappings of the last source map and retrieve
+	// original position for each mapping segment
+	for (let i = 0; i < lastMap.length; i++) {
+		const line = lastMap[i];
+
+		/** @type {import('sourcemap-codec').SourceMapSegment[]} */
+		const rewrittenSegments = [];
+		for (let j = 0; j < line.length; j++) {
+			const segment = line[j];
+
+			if (segment.length === 4) {
+				const original = getOriginalPosition(
+					sourceMaps,
+					parsedMappings,
+					sourcesCache,
+					segment[1],
+					segment[2],
+					segment[3]
+				);
+				rewrittenSegments.push([segment[0], original.source, original.line, original.column]);
+			} else if (segment.length === 5) {
+				const original = getOriginalPosition(
+					sourceMaps,
+					parsedMappings,
+					sourcesCache,
+					segment[1],
+					segment[2],
+					segment[3]
+				);
+				rewrittenSegments.push([segment[0], original.source, original.line, original.column, segment[4]]);
+			} else {
+				rewrittenSegments.push(segment);
+			}
+		}
+
+		outMappings.push(rewrittenSegments);
+	}
+
+	return {
+		version: 3,
+		file,
+		names: Array.from(names.keys()),
+		sourceRoot,
+		sources,
+		sourcesContent,
+		mappings: encode(outMappings)
+	};
+}
diff --git a/packages/wmr/src/lib/transform-imports.js b/packages/wmr/src/lib/transform-imports.js
index d1ef0316c..d2672ccdb 100644
--- a/packages/wmr/src/lib/transform-imports.js
+++ b/packages/wmr/src/lib/transform-imports.js
@@ -1,77 +1,65 @@
-import { parse } from 'es-module-lexer/dist/lexer.js';
+import { parse } from 'es-module-lexer';
+import MagicString from 'magic-string';
+import path from 'path';
 
 /** @template T @typedef {Promise<T>|T} MaybePromise */
 
 /** @typedef {(specifier: string, id?: string) => MaybePromise<string|false|null|void>} ResolveFn */
 
+const KIND_IMPORT = 0;
+const KIND_DYNAMIC_IMPORT = 1;
+const KIND_IMPORT_META = 2;
+
 /**
  * @param {string} code Module code
  * @param {string} id Source module specifier
- * @param {object} [options]
+ * @param {object} options
  * @param {ResolveFn?} [options.resolveImportMeta] Replace `import.meta.FIELD` with a JS string. Return `false`/`null` preserve.
  * @param {ResolveFn?} [options.resolveId] Return a replacement for import specifiers
  * @param {ResolveFn?} [options.resolveDynamicImport] `false` preserves, `null` falls back to resolveId()
+ * @param {boolean} [options.sourcemap]
+ * @returns {Promise<{ code: string, map: any }>}
  */
-export async function transformImports(code, id, { resolveImportMeta, resolveId, resolveDynamicImport } = {}) {
+export async function transformImports(code, id, { resolveImportMeta, resolveId, resolveDynamicImport, sourcemap }) {
 	const [imports] = await parse(code, id);
-	let out = '';
+	const s = new MagicString(code);
 	let offset = 0;
 
-	// Import specifiers are synchronously converted into placeholders.
-	// Resolutions are async+parallel, held in a mapping to their placeholders.
-	let resolveIds = 0;
-	const toResolve = new Map();
-
-	// Get a [deduplicated] placeholder for a specifier and kick off resolution
-	const field = (spec, resolver, a, b) => {
-		const match = toResolve.get(spec);
-		if (match) return match.placeholder;
-		const placeholder = `%%_RESOLVE_#${++resolveIds}#_%%`;
-		toResolve.set(spec, {
-			placeholder,
-			spec,
-			p: resolver(a, b)
-		});
-		return placeholder;
-	};
-
-	// Falls through to resolveId() if null, preserves spec if false
-	const doResolveDynamicImport = async (spec, id) => {
-		let f = resolveDynamicImport && (await resolveDynamicImport(spec, id));
-		if (f == null && resolveId) f = await resolveId(spec, id);
-		return f;
-	};
+	/** @type {Array<{ spec: string, start: number, end: number, kind: number, property: null | string}>} */
+	const toResolve = [];
 
 	for (const item of imports) {
 		// Skip items that were already processed by being wrapped in an import - eg `import(import.meta.url)`
 		if (item.s < offset) continue;
 
-		out += code.substring(offset, item.s);
-
-		const isImportMeta = item.d === -2;
+		let isImportMeta = item.d === -2;
 		const isDynamicImport = item.d > -1;
 
 		if (isDynamicImport) {
 			// Bugfix: `import(import.meta.url)` returns an invalid negative end_offset.
 			// We detect that here and find the closing paren to estimate the offset.
 			if (item.e < 0) {
+				// @ts-ignore
 				item.e = code.indexOf(')', item.s);
+				isImportMeta = true;
 			}
 			// dynamic import() has no statement_end, so we take the position following the closing paren:
+			// @ts-ignore
 			item.se = code.indexOf(')', item.e) + 1;
 		}
 
 		let quote = '';
-		let after = code.substring(item.e, item.se);
 
 		let spec = code.substring(item.s, item.e);
 		offset = item.se;
 
 		// import.meta
 		if (isImportMeta) {
+			offset = item.s + 'import.meta'.length;
 			// Check for *simple* property access immediately following `import.meta`:
 			const r = /\s*\.\s*([a-z_$][a-z0-9_$]*)/gi;
 			r.lastIndex = offset;
+
 			const match = r.exec(code);
 			if (match && match.index === offset) {
 				// advance past it and append it to the "specifier":
@@ -80,10 +68,9 @@ export async function transformImports(code, id, { resolveImportMeta, resolveId,
 				// resolve it:
 				const property = match[1];
 				if (resolveImportMeta) {
-					spec = field(spec, resolveImportMeta, property);
+					toResolve.push({ spec, start: item.s, end: offset, kind: KIND_IMPORT_META, property });
 				}
 			}
-			out += spec;
 			continue;
 		}
 
@@ -106,41 +93,66 @@ export async function transformImports(code, id, { resolveImportMeta, resolveId,
 				if (resolveDynamicImport) {
 					console.warn(`Cannot resolve dynamic expression in import(${spec})`);
 				}
-				out += spec + after;
 				continue;
 			} else {
 				// Trim any import assertions if present so that we just have the
 				// import specifier itself.
 				const closingQuoteIdx = spec.indexOf(quote, 1);
 				spec = spec.slice(0, closingQuoteIdx + 1);
+				// @ts-ignore
+				item.e = code.indexOf(quote, item.s + 1);
 			}
 
 			spec = spec.replace(/^\s*(['"`])(.*)\1\s*$/g, '$2');
 
-			if (resolveDynamicImport) {
-				spec = field(spec, doResolveDynamicImport, spec, id);
-				out += quote + spec + quote + after;
-				continue;
-			}
+			toResolve.push({
+				spec,
+				// Account for opening quote
+				start: item.s + 1,
+				end: item.e,
+				kind: KIND_DYNAMIC_IMPORT,
+				property: null
+			});
+			continue;
 		}
 
 		if (resolveId) {
-			spec = field(spec, resolveId, spec, id);
+			toResolve.push({ spec, start: item.s, end: item.e, kind: KIND_IMPORT, property: null });
 		}
-		out += quote + spec + quote + after;
 	}
 
-	out += code.substring(offset);
-
-	// Wait for all resolutions to finish and map them to placeholders
-	const mapping = new Map();
 	await Promise.all(
-		Array.from(toResolve.values()).map(async v => {
-			mapping.set(v.placeholder, (await v.p) || v.spec);
+		toResolve.map(async v => {
+			let resolved = null;
+			if (v.kind === KIND_IMPORT) {
+				// @ts-ignore
+				resolved = await resolveId(v.spec, id);
+			} else if (v.kind === KIND_DYNAMIC_IMPORT) {
+				// @ts-ignore
+				if (resolveDynamicImport) {
+					resolved = await resolveDynamicImport(v.spec, id);
+				}
+
+				if (resolved == null && resolveId) {
+					resolved = await resolveId(v.spec, id);
+				}
+			} else if (v.kind === KIND_IMPORT_META) {
+				// @ts-ignore
+				resolved = await resolveImportMeta(v.property, id);
+			}
+
+			if (!resolved) return;
+
+			if (v.start !== v.end) {
+				s.overwrite(v.start, v.end, resolved);
+			} else {
+				s.prependLeft(v.start, resolved);
+			}
 		})
 	);
 
-	out = out.replace(/%%_RESOLVE_#\d+#_%%/g, s => mapping.get(s));
-
-	return out;
+	return {
+		code: s.toString(),
+		map: sourcemap ? s.generateMap({ source: id, file: path.posix.basename(id), includeContent: true }) : null
+	};
 }
diff --git a/packages/wmr/src/plugins/htm-plugin.js b/packages/wmr/src/plugins/htm-plugin.js
index 226ca9598..e48377374 100644
--- a/packages/wmr/src/plugins/htm-plugin.js
+++ b/packages/wmr/src/plugins/htm-plugin.js
@@ -8,9 +8,10 @@ import transformJsxToHtmLite from '../lib/transform-jsx-to-htm-lite.js';
  * @param {object} [options]
  * @param {RegExp | ((filename: string) => boolean)} [options.include] Controls whether files are processed to transform JSX.
  * @param {boolean} [options.production = true] If `false`, a simpler whitespace-preserving transform is used.
+ * @param {boolean} [options.sourcemap]
  * @returns {import('rollup').Plugin}
  */
-export default function htmPlugin({ include, production = true } = {}) {
+export default function htmPlugin({ include, production = true, sourcemap } = {}) {
 	return {
 		name: 'htm-plugin',
 
@@ -58,7 +59,9 @@ export default function htmPlugin({ include, production = true } = {}) {
 					]
 				],
 				filename,
-				sourceMaps: true,
+				// Default is to generate sourcemaps, needs an explicit
+				// boolean
+				sourceMaps: !!sourcemap,
 				generatorOpts: {
 					compact: production
 				},
diff --git a/packages/wmr/src/plugins/import-assertion.js b/packages/wmr/src/plugins/import-assertion.js
index 198337063..9e9049091 100644
--- a/packages/wmr/src/plugins/import-assertion.js
+++ b/packages/wmr/src/plugins/import-assertion.js
@@ -13,9 +13,11 @@ import { transform } from '../lib/acorn-traverse.js';
  * import foo from "json:./foo.json";
  * ```
  *
+ * @param {object} options
+ * @param {boolean} options.sourcemap
  * @returns {import("rollup").Plugin}
  */
-export function importAssertionPlugin() {
+export function importAssertionPlugin({ sourcemap }) {
 	return {
 		name: 'import-assertion',
 		options(opts) {
@@ -28,8 +30,13 @@ export function importAssertionPlugin() {
 
 			const res = transform(code, {
 				parse: this.parse,
-				plugins: [transformImportAssertions]
+				plugins: [transformImportAssertions],
+				filename: id,
+				// Default is to generate sourcemaps, needs an explicit
+				// boolean
+				sourceMaps: !!sourcemap
 			});
+
 			return {
 				code: res.code,
 				map: res.map
@@ -45,6 +52,32 @@ function transformImportAssertions({ types: t }) {
 	return {
 		name: 'transform-import-assertions',
 		visitor: {
+			ImportExpression(path) {
+				const args = path.node.arguments;
+				if (!args || !args.length) return;
+				if (!t.isObjectExpression(args[0])) return;
+
+				if (!args[0].properties) return;
+				for (let i = 0; i < args[0].properties.length; i++) {
+					const prop = args[0].properties[i];
+
+					if (!t.isIdentifier(prop.key) || prop.key.name !== 'assert') {
+						continue;
+					}
+
+					if (!t.isObjectExpression(prop.value) || !prop.value.properties || !prop.value.properties.length) {
+						continue;
+					}
+
+					const innerProp = prop.value.properties[0];
+					if (!t.isIdentifier(innerProp.key) || innerProp.key.name !== 'type') {
+						continue;
+					}
+
+					const type = innerProp.value.value;
+					path.replaceWith(t.importExpression(t.stringLiteral(`${type}:${path.node.source.value}`)));
+				}
+			},
 			ImportDeclaration(path) {
 				const { assertions } = path.node;
 				if (assertions && assertions.length > 0) {
diff --git a/packages/wmr/src/plugins/process-global-plugin.js b/packages/wmr/src/plugins/process-global-plugin.js
index f734ab8df..3c8c95a8b 100644
--- a/packages/wmr/src/plugins/process-global-plugin.js
+++ b/packages/wmr/src/plugins/process-global-plugin.js
@@ -1,4 +1,7 @@
+import MagicString from 'magic-string';
+import path from 'path';
 import { transform } from '../lib/acorn-traverse.js';
+import { mergeSourceMaps } from '../lib/sourcemap.js';
 
 /**
  * Plugin to replace `process.env.MY_VAR` or `import.meta.env.MY_VAR` with
@@ -34,12 +37,13 @@ function acornEnvPlugin(env) {
 
 /**
  * Inject process globals and inline process.env.NODE_ENV.
- * @param {object} [options]
+ * @param {object} options
  * @param {string} [options.NODE_ENV] constant to inline for `process.env.NODE_ENV`
  * @param {Record<string, string>} [options.env]
+ * @param {boolean} [options.sourcemap]
  * @returns {import('rollup').Plugin}
  */
-export default function processGlobalPlugin({ NODE_ENV = 'development', env = {} } = {}) {
+export default function processGlobalPlugin({ NODE_ENV = 'development', env = {}, sourcemap }) {
 	const processObj = JSON.stringify({ browser: true, env: { ...env, NODE_ENV } });
 
 	const PREFIX = `\0builtins:`;
@@ -54,30 +58,50 @@ export default function processGlobalPlugin({ NODE_ENV = 'development', env = {}
 		},
 		transform(code, id) {
 			if (!/\.([tj]sx?|mjs)$/.test(id)) return;
-			const orig = code;
 
 			const result = transform(code, {
 				plugins: [acornEnvPlugin({ ...env, NODE_ENV })],
-				parse: this.parse
+				parse: this.parse,
+				filename: id,
+				// Default is to generate sourcemaps, needs an explicit
+				// boolean
+				sourceMaps: !!sourcemap
 			});
 
 			code = result.code;
 
+			const s = new MagicString(code);
+
 			// if that wasn't the only way `process.env` was referenced...
 			if (code.match(/[^a-zA-Z0-9]process\.env/)) {
 				// hack: avoid injecting imports into commonjs modules
 				if (/^\s*(import|export)[\s{]/gm.test(code)) {
+					s.prepend(`import process from '${PREFIX}process.js';\n`);
 					code = `import process from '${PREFIX}process.js';${code}`;
 				} else {
+					s.prepend(`var process=${processObj};\n`);
 					code = `var process=${processObj};${code}`;
 				}
 			}
 
-			code = code.replace(/typeof(\s+|\s*\(+\s*)process([^a-zA-Z$_])/g, 'typeof$1undefined$2');
-
-			if (code !== orig) {
-				return { code, map: null };
+			const reg = /typeof(\s+|\s*\(+\s*)process([^a-zA-Z$_])/g;
+			let match = null;
+			while ((match = reg.exec(code)) !== null) {
+				s.overwrite(match.index, match[0].length, 'typeof$1undefined$2');
 			}
+
+			/** @type {*} */
+			const map = sourcemap
+				? mergeSourceMaps([
+						result.map,
+						s.generateMap({ source: id, file: path.posix.basename(id), includeContent: true })
+				  ])
+				: null;
+
+			return {
+				code: s.toString(),
+				map
+			};
 		}
 	};
 }
diff --git a/packages/wmr/src/plugins/sucrase-plugin.js b/packages/wmr/src/plugins/sucrase-plugin.js
index 939519b0d..5d282c253 100644
--- a/packages/wmr/src/plugins/sucrase-plugin.js
+++ b/packages/wmr/src/plugins/sucrase-plugin.js
@@ -56,9 +56,15 @@ export default function sucrasePlugin(opts = {}) {
 						: undefined
 				});
 
+				let sourceMap = null;
+				if (opts.sourcemap && result.sourceMap) {
+					result.sourceMap.sourcesContent = [code];
+					sourceMap = result.sourceMap;
+				}
+
 				return {
 					code: result.code,
-					map: opts.sourcemap ? result.sourceMap : null
+					map: sourceMap
 				};
 			} catch (err) {
 				// Enhance error with code frame
diff --git a/packages/wmr/src/plugins/wmr/plugin.js b/packages/wmr/src/plugins/wmr/plugin.js
index b45951639..ea2a3db8d 100644
--- a/packages/wmr/src/plugins/wmr/plugin.js
+++ b/packages/wmr/src/plugins/wmr/plugin.js
@@ -1,5 +1,6 @@
 import { promises as fs } from 'fs';
 import MagicString from 'magic-string';
+import path from 'path';
 import { ESM_KEYWORDS } from '../fast-cjs-plugin.js';
 
 const BYPASS_HMR = process.env.BYPASS_HMR === 'true';
@@ -35,9 +36,12 @@ export function getWmrClient({ hot = true } = {}) {
  * Implements Hot Module Replacement.
  * Conforms to the {@link esm-hmr https://github.com/pikapkg/esm-hmr} spec.
  * @param {object} options
+ * @param {boolean} [options.hot]
+ * @param {boolean} [options.preact]
+ * @param {boolean} [options.sourcemap]
  * @returns {import('rollup').Plugin}
  */
-export default function wmrPlugin({ hot = true, preact } = {}) {
+export default function wmrPlugin({ hot = true, preact, sourcemap } = {}) {
 	if (BYPASS_HMR) hot = false;
 
 	return {
@@ -102,7 +106,7 @@ export default function wmrPlugin({ hot = true, preact } = {}) {
 
 			return {
 				code: s.toString(),
-				map: s.generateMap({ includeContent: false })
+				map: sourcemap ? s.generateMap({ source: id, file: path.posix.basename(id), includeContent: true }) : null
 			};
 		}
 	};
diff --git a/packages/wmr/src/plugins/wmr/styles/styles-plugin.js b/packages/wmr/src/plugins/wmr/styles/styles-plugin.js
index 378eddfda..a38f7fdf8 100644
--- a/packages/wmr/src/plugins/wmr/styles/styles-plugin.js
+++ b/packages/wmr/src/plugins/wmr/styles/styles-plugin.js
@@ -15,10 +15,11 @@ const RESERVED_WORDS = /^(abstract|async|boolean|break|byte|case|catch|char|clas
  * @param {string} options.root Manually specify the cwd from which to resolve filenames (important for calculating hashes!)
  * @param {boolean} [options.hot] Indicates the plugin should inject a HMR-runtime
  * @param {boolean} [options.production]
+ * @param {boolean} [options.sourcemap]
  * @param {Record<string, string>} options.alias
  * @returns {import('rollup').Plugin}
  */
-export default function wmrStylesPlugin({ root, hot, production, alias }) {
+export default function wmrStylesPlugin({ root, hot, production, alias, sourcemap }) {
 	let assetId = 0;
 	const assetMap = new Map();
 	/** @type {Map<string, Set<string>>} */
@@ -149,7 +150,14 @@ export default function wmrStylesPlugin({ root, hot, production, alias }) {
 				code,
 				moduleSideEffects: true,
 				syntheticNamedExports: true,
-				map: null
+				map: sourcemap
+					? {
+							version: 3,
+							sources: [],
+							mappings: '',
+							names: []
+					  }
+					: null
 			};
 		},
 		async generateBundle(_, bundle) {
diff --git a/packages/wmr/src/server.js b/packages/wmr/src/server.js
index b111528c8..82ccc9733 100644
--- a/packages/wmr/src/server.js
+++ b/packages/wmr/src/server.js
@@ -106,6 +106,20 @@ export default async function server({ cwd, root, overlayDir, middleware, http2,
 
 	app.use('/@npm', npmMiddleware({ alias, optimize, cwd }));
 
+	// Chrome devtools often adds `?%20[sm]` to the url
+	// to differentiate between sourcemaps
+	app.use((req, res, next) => {
+		if (/\?%20\[sm\]$/.test(req.url)) {
+			res.writeHead(302, {
+				Location: req.url.replace('?%20[sm]', '.map')
+			});
+			res.end();
+			return;
+		}
+
+		next();
+	});
+
 	if (middleware) {
 		app.use(...middleware);
 	}
diff --git a/packages/wmr/src/wmr-middleware.js b/packages/wmr/src/wmr-middleware.js
index 1ff637a2a..bab2db3ff 100644
--- a/packages/wmr/src/wmr-middleware.js
+++ b/packages/wmr/src/wmr-middleware.js
@@ -11,6 +11,7 @@ import { getPlugins } from './lib/plugins.js';
 import { watch } from './lib/fs-watcher.js';
 import { matchAlias, resolveAlias } from './lib/aliasing.js';
 import { addTimestamp } from './lib/net-utils.js';
+import { mergeSourceMaps } from './lib/sourcemap.js';
 
 const NOOP = () => {};
 
@@ -32,12 +33,13 @@ export const moduleGraph = new Map();
  * @returns {import('polka').Middleware}
  */
 export default function wmrMiddleware(options) {
-	let { cwd, root, out, distDir = 'dist', onError, onChange = NOOP, alias } = options;
+	let { cwd, root, out, distDir = 'dist', onError, onChange = NOOP, alias, sourcemap } = options;
 
 	distDir = resolve(dirname(out), distDir);
 
 	const NonRollup = createPluginContainer(getPlugins(options), {
 		cwd: root,
+		sourcemap,
 		writeFile: (filename, source) => {
 			// Remove .cache folder from filename if present. The cache
 			// works with relative keys only.
@@ -155,6 +157,16 @@ export default function wmrMiddleware(options) {
 			logCache(`delete: ${kl.cyan(file)}`);
 			WRITE_CACHE.delete(file);
 
+			// Delete source file if there is any
+			if (options.sourcemap) {
+				const sourceKey = file + '.map';
+
+				if (WRITE_CACHE.has(sourceKey)) {
+					logCache(`delete: ${kl.cyan(sourceKey)}`);
+					WRITE_CACHE.delete(sourceKey);
+				}
+			}
+
 			// We could be dealing with an asset
 			if (WRITE_CACHE.has(file + '?asset')) {
 				const cacheKey = file + '?asset';
@@ -281,6 +293,8 @@ export default function wmrMiddleware(options) {
 		let transform;
 		if (path === '/_wmr.js') {
 			transform = getWmrClient.bind(null);
+		} else if (/\.map$/.test(path)) {
+			transform = TRANSFORMS.asset;
 		} else if (queryParams.has('asset')) {
 			cacheKey += '?asset';
 			transform = TRANSFORMS.asset;
@@ -473,11 +487,16 @@ export const TRANSFORMS = {
 				file = file.split(posix.sep).join(sep);
 				if (!isAbsolute(file)) file = resolve(root, file);
 				code = await fs.readFile(resolveFile(file, root, alias), 'utf-8');
+
+				// TODO: Optional: Load sourcemap
 			}
 
-			code = await NonRollup.transform(code, id);
+			const transformed = await NonRollup.transform(code, id);
+			code = transformed.code;
+			/** @type {import('rollup').ExistingRawSourceMap | null} */
+			let sourceMap = transformed.map;
 
-			code = await transformImports(code, id, {
+			const rewritten = await transformImports(code, id, {
 				resolveImportMeta(property) {
 					return NonRollup.resolveImportMeta(property);
 				},
@@ -598,6 +617,20 @@ export const TRANSFORMS = {
 				}
 			});
 
+			if (rewritten.map !== null) {
+				if (sourceMap !== null) {
+					// @ts-ignore
+					sourceMap = mergeSourceMaps([sourceMap, rewritten.map]);
+				} else {
+					sourceMap = rewritten.map;
+				}
+			}
+			code = rewritten.code;
+
+			if (sourceMap !== null) {
+				writeCacheFile(cacheKey + '.map', JSON.stringify(sourceMap));
+				code = `${code}\n//# sourceMappingURL=${basename(id)}.map`;
+			}
 			writeCacheFile(cacheKey, code);
 
 			return code;
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import-inline.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import-inline.expected.js
new file mode 100644
index 000000000..4d9bb656b
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import-inline.expected.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+const About = lazy(() => import('it_works'));
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import-inline.js b/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import-inline.js
new file mode 100644
index 000000000..b74f3689a
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import-inline.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+const About = lazy(() => import('./pages/about/index.js'));
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import.expected.js
new file mode 100644
index 000000000..c8aee9c09
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import.expected.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import('it_works');
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import.js b/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import.js
new file mode 100644
index 000000000..131dc8297
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/dynamic-import.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import('foo');
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion-dynamic.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion-dynamic.expected.js
new file mode 100644
index 000000000..b2b855c00
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion-dynamic.expected.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import('it_works_dynamic', { assert: { type: 'json' } });
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion-dynamic.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion-dynamic.js
new file mode 100644
index 000000000..53ea85211
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion-dynamic.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import('foo', { assert: { type: 'json' } });
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion.expected.js
new file mode 100644
index 000000000..6411ad23a
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion.expected.js
@@ -0,0 +1 @@
+import json from 'it_works' assert { type: 'json' };
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion.js
new file mode 100644
index 000000000..39bc625b3
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-assertion.js
@@ -0,0 +1 @@
+import json from './foo.json' assert { type: 'json' };
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-inline.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-inline.expected.js
new file mode 100644
index 000000000..33df6da16
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-inline.expected.js
@@ -0,0 +1,7 @@
+// @ts-ignore
+let m = import(foo);
+// @ts-ignore
+bar.accept(async ({ module }) => {
+	// @ts-ignore
+	m = await m;
+});
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-inline.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-inline.js
new file mode 100644
index 000000000..041bb7d9a
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-inline.js
@@ -0,0 +1,7 @@
+// @ts-ignore
+let m = import(import.meta.url);
+// @ts-ignore
+import.meta.hot.accept(async ({ module }) => {
+	// @ts-ignore
+	m = await m;
+});
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-long.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-long.expected.js
new file mode 100644
index 000000000..daef2a221
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-long.expected.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import(it_works.NODE_ENV);
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-long.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-long.js
new file mode 100644
index 000000000..d9f11432d
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta-long.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import(import.meta.env.NODE_ENV);
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-meta.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta.expected.js
new file mode 100644
index 000000000..b2a661669
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta.expected.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import(it_works);
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/import-meta.js b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta.js
new file mode 100644
index 000000000..749f930c9
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/import-meta.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import(import.meta.foo);
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/static-import-empty.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/static-import-empty.expected.js
new file mode 100644
index 000000000..22c3d2111
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/static-import-empty.expected.js
@@ -0,0 +1,5 @@
+// @ts-ignore
+import { foo } from 'foo';
+// @ts-ignore
+import bar from 'foo';
+import 'foo';
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/static-import-empty.js b/packages/wmr/test/fixtures/_unit-transform-imports/static-import-empty.js
new file mode 100644
index 000000000..a3c778afe
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/static-import-empty.js
@@ -0,0 +1,5 @@
+// @ts-ignore
+import { foo } from '';
+// @ts-ignore
+import bar from '';
+import '';
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/static-import-relative.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/static-import-relative.expected.js
new file mode 100644
index 000000000..4f3966abc
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/static-import-relative.expected.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import { foo } from 'it_works';
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/static-import-relative.js b/packages/wmr/test/fixtures/_unit-transform-imports/static-import-relative.js
new file mode 100644
index 000000000..611acc0a8
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/static-import-relative.js
@@ -0,0 +1,2 @@
+// @ts-ignore
+import { foo } from './foo.js?module';
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/static-import.expected.js b/packages/wmr/test/fixtures/_unit-transform-imports/static-import.expected.js
new file mode 100644
index 000000000..b40f293fe
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/static-import.expected.js
@@ -0,0 +1,5 @@
+// @ts-ignore
+import { foo } from 'a';
+// @ts-ignore
+import bar from 'b';
+import 'c';
diff --git a/packages/wmr/test/fixtures/_unit-transform-imports/static-import.js b/packages/wmr/test/fixtures/_unit-transform-imports/static-import.js
new file mode 100644
index 000000000..f94f620be
--- /dev/null
+++ b/packages/wmr/test/fixtures/_unit-transform-imports/static-import.js
@@ -0,0 +1,5 @@
+// @ts-ignore
+import { foo } from 'foo';
+// @ts-ignore
+import bar from 'bar';
+import 'baz';
diff --git a/packages/wmr/test/fixtures/sourcemap-jsx/index.html b/packages/wmr/test/fixtures/sourcemap-jsx/index.html
new file mode 100644
index 000000000..bd2a2bce2
--- /dev/null
+++ b/packages/wmr/test/fixtures/sourcemap-jsx/index.html
@@ -0,0 +1,2 @@
+<div id="out">it doesn't work</div>
+<script src="./index.jsx" type="module"></script>
diff --git a/packages/wmr/test/fixtures/sourcemap-jsx/index.jsx b/packages/wmr/test/fixtures/sourcemap-jsx/index.jsx
new file mode 100644
index 000000000..623537a74
--- /dev/null
+++ b/packages/wmr/test/fixtures/sourcemap-jsx/index.jsx
@@ -0,0 +1,8 @@
+import { render } from 'preact';
+
+function App() {
+	return <h1>it works</h1>;
+}
+
+document.getElementById('out').textContent = '';
+render(<App />, document.getElementById('out'));
diff --git a/packages/wmr/test/fixtures/sourcemap-ts/index.html b/packages/wmr/test/fixtures/sourcemap-ts/index.html
new file mode 100644
index 000000000..950511873
--- /dev/null
+++ b/packages/wmr/test/fixtures/sourcemap-ts/index.html
@@ -0,0 +1,2 @@
+<pre id="out">it doesn't work</pre>
+<script src="./index.ts" type="module"></script>
diff --git a/packages/wmr/test/fixtures/sourcemap-ts/index.ts b/packages/wmr/test/fixtures/sourcemap-ts/index.ts
new file mode 100644
index 000000000..b77d1d853
--- /dev/null
+++ b/packages/wmr/test/fixtures/sourcemap-ts/index.ts
@@ -0,0 +1,9 @@
+export interface Foo {
+	foo: string;
+}
+
+function getFoo(foo: Foo) {
+	return foo.foo;
+}
+
+document.getElementById('out').textContent = getFoo({ foo: 'it works' });
diff --git a/packages/wmr/test/sourcemaps.test.js b/packages/wmr/test/sourcemaps.test.js
new file mode 100644
index 000000000..f770217c5
--- /dev/null
+++ b/packages/wmr/test/sourcemaps.test.js
@@ -0,0 +1,72 @@
+import { setupTest, teardown, loadFixture, runWmrFast, getOutput, withLog } from './test-helpers.js';
+
+jest.setTimeout(30000);
+
+describe('sourcemaps', () => {
+	/** @type {TestEnv} */
+	let env;
+	/** @type {WmrInstance} */
+	let instance;
+
+	beforeEach(async () => {
+		env = await setupTest();
+	});
+
+	afterEach(async () => {
+		await teardown(env);
+		instance.close();
+	});
+
+	it('should import absolute file', async () => {
+		await loadFixture('sourcemap-ts', env);
+		instance = await runWmrFast(env.tmp.path, '--sourcemap');
+
+		await withLog(instance.output, async () => {
+			expect(await getOutput(env, instance)).toMatch(/it works/);
+			expect(await env.page.evaluate('fetch("/index.ts.map").then(r => r.json())')).toEqual({
+				file: 'index.ts',
+				mappings: 'AAAA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;',
+				names: [],
+				sources: ['/index.ts'],
+				sourcesContent: [
+					`export interface Foo {
+	foo: string;
+}
+
+function getFoo(foo: Foo) {
+	return foo.foo;
+}
+
+document.getElementById('out').textContent = getFoo({ foo: 'it works' });\n`
+				],
+				version: 3
+			});
+		});
+	});
+
+	it('should map jsx', async () => {
+		await loadFixture('sourcemap-jsx', env);
+		instance = await runWmrFast(env.tmp.path, '--sourcemap');
+
+		await withLog(instance.output, async () => {
+			expect(await getOutput(env, instance)).toMatch(/it works/);
+			expect(await env.page.evaluate('fetch("/index.jsx.map").then(r => r.json())')).toEqual({
+				file: 'index.jsx',
+				mappings: 'AAAA;AAAA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;',
+				names: [],
+				sources: ['/index.jsx'],
+				sourcesContent: [
+					`import { render } from 'preact';
+
+function App() {
+	return <h1>it works</h1>;
+}
+
+document.getElementById('out').textContent = '';
+render(<App />, document.getElementById('out'));\n`
+				],
+				version: 3
+			});
+		});
+	});
+});
diff --git a/packages/wmr/test/transform-imports.test.js b/packages/wmr/test/transform-imports.test.js
new file mode 100644
index 000000000..905070a85
--- /dev/null
+++ b/packages/wmr/test/transform-imports.test.js
@@ -0,0 +1,182 @@
+import path from 'path';
+import { promises as fs } from 'fs';
+import { transformImports } from '../src/lib/transform-imports.js';
+
+/**
+ * @param {string} file
+ * @returns {Promise<string>}
+ */
+async function readFile(file) {
+	return fs.readFile(path.join(__dirname, 'fixtures', '_unit-transform-imports', file), 'utf-8');
+}
+
+describe('transformImports', () => {
+	it('should generate source maps', async () => {
+		const code = await readFile('static-import.js');
+		const result = await transformImports(code, 'my-test', {
+			sourcemap: true,
+			resolveId(id) {
+				if (id === 'foo') return 'a';
+				if (id === 'bar') return 'b';
+				if (id === 'baz') return 'c';
+				return 'nope';
+			}
+		});
+		expect(result.map).not.toEqual(null);
+	});
+
+	describe('import statement', () => {
+		it('should transform imports', async () => {
+			const code = await readFile('static-import.js');
+			const expected = await readFile('static-import.expected.js');
+			const result = await transformImports(code, 'my-test', {
+				resolveId(id) {
+					if (id === 'foo') return 'a';
+					if (id === 'bar') return 'b';
+					if (id === 'baz') return 'c';
+					return 'nope';
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+
+		it('should transform empty imports', async () => {
+			const code = await readFile('static-import-empty.js');
+			const expected = await readFile('static-import-empty.expected.js');
+			const result = await transformImports(code, 'my-test', {
+				resolveId() {
+					return 'foo';
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+
+		it('should preserve relative spec', async () => {
+			const code = await readFile('static-import-relative.js');
+			const expected = await readFile('static-import-relative.expected.js');
+
+			const result = await transformImports(code, 'my-test', {
+				resolveId(id) {
+					if (id === './foo.js?module') {
+						return 'it_works';
+					}
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+	});
+
+	describe('dynamic import', () => {
+		it('should transform imports', async () => {
+			const code = await readFile('dynamic-import.js');
+			const expected = await readFile('dynamic-import.expected.js');
+			const result = await transformImports(code, 'my-test', {
+				resolveDynamicImport(id) {
+					if (id === 'foo') {
+						return 'it_works';
+					}
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+
+		it('should transform inline', async () => {
+			const code = await readFile('dynamic-import-inline.js');
+			const expected = await readFile('dynamic-import-inline.expected.js');
+			const result = await transformImports(code, 'my-test', {
+				resolveDynamicImport(id) {
+					if (id === './pages/about/index.js') {
+						return 'it_works';
+					}
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+	});
+
+	describe('import.meta', () => {
+		it('should transform simple property', async () => {
+			const code = await readFile('import-meta.js');
+			const expected = await readFile('import-meta.expected.js');
+			const result = await transformImports(code, 'my-test', {
+				resolveImportMeta(property) {
+					if (property === 'foo') {
+						return 'it_works';
+					}
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+
+		it('should transform nested property', async () => {
+			const code = await readFile('import-meta-long.js');
+			const expected = await readFile('import-meta-long.expected.js');
+			const result = await transformImports(code, 'my-test', {
+				resolveImportMeta(property) {
+					if (property === 'env') {
+						return 'it_works';
+					}
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+
+		it('should transform inline', async () => {
+			const code = await readFile('import-meta-inline.js');
+			const expected = await readFile('import-meta-inline.expected.js');
+			const result = await transformImports(code, 'my-test', {
+				resolveId(id) {
+					throw new Error(`Called resolveId(${id})`);
+				},
+				resolveDynamicImport(id) {
+					throw new Error(`Called resolveDynamicImport(${id})`);
+				},
+				resolveImportMeta(property) {
+					if (property === 'url') {
+						return 'foo';
+					} else if (property === 'hot') {
+						return 'bar';
+					}
+					return 'nope';
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+	});
+
+	describe('import assertions', () => {
+		it('should ignore in static imports', async () => {
+			const code = await readFile('import-assertion.js');
+			const expected = await readFile('import-assertion.expected.js');
+			const result = await transformImports(code, 'my-test', {
+				resolveId() {
+					return 'it_works';
+				},
+				resolveDynamicImport() {
+					return 'it_works_dynamic';
+				},
+				resolveImportMeta() {
+					return 'it_works_meta';
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+
+		it('should ignore in dynamic imports', async () => {
+			const code = await readFile('import-assertion-dynamic.js');
+			const expected = await readFile('import-assertion-dynamic.expected.js');
+			const result = await transformImports(code, 'my-test', {
+				resolveId() {
+					return 'it_works';
+				},
+				resolveDynamicImport() {
+					return 'it_works_dynamic';
+				},
+				resolveImportMeta() {
+					return 'it_works_meta';
+				}
+			});
+			expect(result.code).toEqual(expected);
+		});
+	});
+});
diff --git a/patches/es-module-lexer+0.4.1.patch b/patches/es-module-lexer+0.4.1.patch
new file mode 100644
index 000000000..d5103875e
--- /dev/null
+++ b/patches/es-module-lexer+0.4.1.patch
@@ -0,0 +1,19 @@
+diff --git a/node_modules/es-module-lexer/package.json b/node_modules/es-module-lexer/package.json
+index 0c49d6e..4b9d388 100755
+--- a/node_modules/es-module-lexer/package.json
++++ b/node_modules/es-module-lexer/package.json
+@@ -5,6 +5,14 @@
+   "main": "dist/lexer.cjs",
+   "module": "dist/lexer.js",
+   "types": "types/lexer.d.ts",
++	"exports": {
++    ".": {
++      "import": "./dist/lexer.js",
++      "require": "./dist/lexer.cjs"
++    },
++    "./package.json": "./package.json",
++    "./": "./"
++  },
+   "scripts": {
+     "test": "NODE_OPTIONS=\"--experimental-modules\" mocha -b -u tdd test/*.cjs",
+     "build": "node --experimental-modules build.js && babel dist/lexer.js | terser -o dist/lexer.cjs",
diff --git a/patches/sourcemap-codec+1.4.8.patch b/patches/sourcemap-codec+1.4.8.patch
new file mode 100644
index 000000000..5c5117ea6
--- /dev/null
+++ b/patches/sourcemap-codec+1.4.8.patch
@@ -0,0 +1,162 @@
+diff --git a/node_modules/sourcemap-codec/.DS_Store b/node_modules/sourcemap-codec/.DS_Store
+new file mode 100644
+index 0000000..f7b71aa
+Binary files /dev/null and b/node_modules/sourcemap-codec/.DS_Store differ
+diff --git a/node_modules/sourcemap-codec/dist/sourcemap-codec.mjs b/node_modules/sourcemap-codec/dist/sourcemap-codec.mjs
+new file mode 100644
+index 0000000..4e3813e
+--- /dev/null
++++ b/node_modules/sourcemap-codec/dist/sourcemap-codec.mjs
+@@ -0,0 +1,124 @@
++var charToInteger = {};
++var chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
++for (var i = 0; i < chars.length; i++) {
++    charToInteger[chars.charCodeAt(i)] = i;
++}
++function decode(mappings) {
++    var decoded = [];
++    var line = [];
++    var segment = [
++        0,
++        0,
++        0,
++        0,
++        0,
++    ];
++    var j = 0;
++    for (var i = 0, shift = 0, value = 0; i < mappings.length; i++) {
++        var c = mappings.charCodeAt(i);
++        if (c === 44) { // ","
++            segmentify(line, segment, j);
++            j = 0;
++        }
++        else if (c === 59) { // ";"
++            segmentify(line, segment, j);
++            j = 0;
++            decoded.push(line);
++            line = [];
++            segment[0] = 0;
++        }
++        else {
++            var integer = charToInteger[c];
++            if (integer === undefined) {
++                throw new Error('Invalid character (' + String.fromCharCode(c) + ')');
++            }
++            var hasContinuationBit = integer & 32;
++            integer &= 31;
++            value += integer << shift;
++            if (hasContinuationBit) {
++                shift += 5;
++            }
++            else {
++                var shouldNegate = value & 1;
++                value >>>= 1;
++                if (shouldNegate) {
++                    value = value === 0 ? -0x80000000 : -value;
++                }
++                segment[j] += value;
++                j++;
++                value = shift = 0; // reset
++            }
++        }
++    }
++    segmentify(line, segment, j);
++    decoded.push(line);
++    return decoded;
++}
++function segmentify(line, segment, j) {
++    // This looks ugly, but we're creating specialized arrays with a specific
++    // length. This is much faster than creating a new array (which v8 expands to
++    // a capacity of 17 after pushing the first item), or slicing out a subarray
++    // (which is slow). Length 4 is assumed to be the most frequent, followed by
++    // length 5 (since not everything will have an associated name), followed by
++    // length 1 (it's probably rare for a source substring to not have an
++    // associated segment data).
++    if (j === 4)
++        line.push([segment[0], segment[1], segment[2], segment[3]]);
++    else if (j === 5)
++        line.push([segment[0], segment[1], segment[2], segment[3], segment[4]]);
++    else if (j === 1)
++        line.push([segment[0]]);
++}
++function encode(decoded) {
++    var sourceFileIndex = 0; // second field
++    var sourceCodeLine = 0; // third field
++    var sourceCodeColumn = 0; // fourth field
++    var nameIndex = 0; // fifth field
++    var mappings = '';
++    for (var i = 0; i < decoded.length; i++) {
++        var line = decoded[i];
++        if (i > 0)
++            mappings += ';';
++        if (line.length === 0)
++            continue;
++        var generatedCodeColumn = 0; // first field
++        var lineMappings = [];
++        for (var _i = 0, line_1 = line; _i < line_1.length; _i++) {
++            var segment = line_1[_i];
++            var segmentMappings = encodeInteger(segment[0] - generatedCodeColumn);
++            generatedCodeColumn = segment[0];
++            if (segment.length > 1) {
++                segmentMappings +=
++                    encodeInteger(segment[1] - sourceFileIndex) +
++                        encodeInteger(segment[2] - sourceCodeLine) +
++                        encodeInteger(segment[3] - sourceCodeColumn);
++                sourceFileIndex = segment[1];
++                sourceCodeLine = segment[2];
++                sourceCodeColumn = segment[3];
++            }
++            if (segment.length === 5) {
++                segmentMappings += encodeInteger(segment[4] - nameIndex);
++                nameIndex = segment[4];
++            }
++            lineMappings.push(segmentMappings);
++        }
++        mappings += lineMappings.join(',');
++    }
++    return mappings;
++}
++function encodeInteger(num) {
++    var result = '';
++    num = num < 0 ? (-num << 1) | 1 : num << 1;
++    do {
++        var clamped = num & 31;
++        num >>>= 5;
++        if (num > 0) {
++            clamped |= 32;
++        }
++        result += chars[clamped];
++    } while (num > 0);
++    return result;
++}
++
++export { decode, encode };
++//# sourceMappingURL=sourcemap-codec.mjs.map
+diff --git a/node_modules/sourcemap-codec/dist/sourcemap-codec.mjs.map b/node_modules/sourcemap-codec/dist/sourcemap-codec.mjs.map
+new file mode 100644
+index 0000000..5b2c6ed
+--- /dev/null
++++ b/node_modules/sourcemap-codec/dist/sourcemap-codec.mjs.map
+@@ -0,0 +1 @@
++{"version":3,"file":"sourcemap-codec.mjs","sources":["../src/sourcemap-codec.ts"],"sourcesContent":["export type SourceMapSegment =\n\t| [number]\n\t| [number, number, number, number]\n\t| [number, number, number, number, number];\nexport type SourceMapLine = SourceMapSegment[];\nexport type SourceMapMappings = SourceMapLine[];\n\nconst charToInteger: { [charCode: number]: number } = {};\nconst chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';\n\nfor (let i = 0; i < chars.length; i++) {\n\tcharToInteger[chars.charCodeAt(i)] = i;\n}\n\nexport function decode(mappings: string): SourceMapMappings {\n\tconst decoded: SourceMapMappings = [];\n\tlet line: SourceMapLine = [];\n\tconst segment: SourceMapSegment = [\n\t\t0, // generated code column\n\t\t0, // source file index\n\t\t0, // source code line\n\t\t0, // source code column\n\t\t0, // name index\n\t];\n\n\tlet j = 0;\n\tfor (let i = 0, shift = 0, value = 0; i < mappings.length; i++) {\n\t\tconst c = mappings.charCodeAt(i);\n\n\t\tif (c === 44) { // \",\"\n\t\t\tsegmentify(line, segment, j);\n\t\t\tj = 0;\n\n\t\t} else if (c === 59) { // \";\"\n\t\t\tsegmentify(line, segment, j);\n\t\t\tj = 0;\n\t\t\tdecoded.push(line);\n\t\t\tline = [];\n\t\t\tsegment[0] = 0;\n\n\t\t} else {\n\t\t\tlet integer = charToInteger[c];\n\t\t\tif (integer === undefined) {\n\t\t\t\tthrow new Error('Invalid character (' + String.fromCharCode(c) + ')');\n\t\t\t}\n\n\t\t\tconst hasContinuationBit = integer & 32;\n\n\t\t\tinteger &= 31;\n\t\t\tvalue += integer << shift;\n\n\t\t\tif (hasContinuationBit) {\n\t\t\t\tshift += 5;\n\t\t\t} else {\n\t\t\t\tconst shouldNegate = value & 1;\n\t\t\t\tvalue >>>= 1;\n\n\t\t\t\tif (shouldNegate) {\n\t\t\t\t\tvalue = value === 0 ? -0x80000000 : -value;\n\t\t\t\t}\n\n\t\t\t\tsegment[j] += value;\n\t\t\t\tj++;\n\t\t\t\tvalue = shift = 0; // reset\n\t\t\t}\n\t\t}\n\t}\n\n\tsegmentify(line, segment, j);\n\tdecoded.push(line);\n\n\treturn decoded;\n}\n\nfunction segmentify(line: SourceMapSegment[], segment: SourceMapSegment, j: number) {\n\t// This looks ugly, but we're creating specialized arrays with a specific\n\t// length. This is much faster than creating a new array (which v8 expands to\n\t// a capacity of 17 after pushing the first item), or slicing out a subarray\n\t// (which is slow). Length 4 is assumed to be the most frequent, followed by\n\t// length 5 (since not everything will have an associated name), followed by\n\t// length 1 (it's probably rare for a source substring to not have an\n\t// associated segment data).\n\tif (j === 4) line.push([segment[0], segment[1], segment[2], segment[3]]);\n\telse if (j === 5) line.push([segment[0], segment[1], segment[2], segment[3], segment[4]]);\n\telse if (j === 1) line.push([segment[0]]);\n}\n\nexport function encode(decoded: SourceMapMappings): string {\n\tlet sourceFileIndex = 0;  // second field\n\tlet sourceCodeLine = 0;   // third field\n\tlet sourceCodeColumn = 0; // fourth field\n\tlet nameIndex = 0;        // fifth field\n\tlet mappings = '';\n\n\tfor (let i = 0; i < decoded.length; i++) {\n\t\tconst line = decoded[i];\n\t\tif (i > 0) mappings += ';';\n\t\tif (line.length === 0) continue;\n\n\t\tlet generatedCodeColumn = 0; // first field\n\n\t\tconst lineMappings: string[] = [];\n\n\t\tfor (const segment of line) {\n\t\t\tlet segmentMappings = encodeInteger(segment[0] - generatedCodeColumn);\n\t\t\tgeneratedCodeColumn = segment[0];\n\n\t\t\tif (segment.length > 1) {\n\t\t\t\tsegmentMappings +=\n\t\t\t\t\tencodeInteger(segment[1] - sourceFileIndex) +\n\t\t\t\t\tencodeInteger(segment[2] - sourceCodeLine) +\n\t\t\t\t\tencodeInteger(segment[3] - sourceCodeColumn);\n\n\t\t\t\tsourceFileIndex = segment[1];\n\t\t\t\tsourceCodeLine = segment[2];\n\t\t\t\tsourceCodeColumn = segment[3];\n\t\t\t}\n\n\t\t\tif (segment.length === 5) {\n\t\t\t\tsegmentMappings += encodeInteger(segment[4] - nameIndex);\n\t\t\t\tnameIndex = segment[4];\n\t\t\t}\n\n\t\t\tlineMappings.push(segmentMappings);\n\t\t}\n\n\t\tmappings += lineMappings.join(',');\n\t}\n\n\treturn mappings;\n}\n\nfunction encodeInteger(num: number): string {\n\tvar result = '';\n\tnum = num < 0 ? (-num << 1) | 1 : num << 1;\n\tdo {\n\t\tvar clamped = num & 31;\n\t\tnum >>>= 5;\n\t\tif (num > 0) {\n\t\t\tclamped |= 32;\n\t\t}\n\t\tresult += chars[clamped];\n\t} while (num > 0);\n\n\treturn result;\n}\n"],"names":[],"mappings":"AAOA,IAAM,aAAa,GAAmC,EAAE,CAAC;AACzD,IAAM,KAAK,GAAG,mEAAmE,CAAC;AAElF,KAAK,IAAI,CAAC,GAAG,CAAC,EAAE,CAAC,GAAG,KAAK,CAAC,MAAM,EAAE,CAAC,EAAE,EAAE;IACtC,aAAa,CAAC,KAAK,CAAC,UAAU,CAAC,CAAC,CAAC,CAAC,GAAG,CAAC,CAAC;CACvC;SAEe,MAAM,CAAC,QAAgB;IACtC,IAAM,OAAO,GAAsB,EAAE,CAAC;IACtC,IAAI,IAAI,GAAkB,EAAE,CAAC;IAC7B,IAAM,OAAO,GAAqB;QACjC,CAAC;QACD,CAAC;QACD,CAAC;QACD,CAAC;QACD,CAAC;KACD,CAAC;IAEF,IAAI,CAAC,GAAG,CAAC,CAAC;IACV,KAAK,IAAI,CAAC,GAAG,CAAC,EAAE,KAAK,GAAG,CAAC,EAAE,KAAK,GAAG,CAAC,EAAE,CAAC,GAAG,QAAQ,CAAC,MAAM,EAAE,CAAC,EAAE,EAAE;QAC/D,IAAM,CAAC,GAAG,QAAQ,CAAC,UAAU,CAAC,CAAC,CAAC,CAAC;QAEjC,IAAI,CAAC,KAAK,EAAE,EAAE;YACb,UAAU,CAAC,IAAI,EAAE,OAAO,EAAE,CAAC,CAAC,CAAC;YAC7B,CAAC,GAAG,CAAC,CAAC;SAEN;aAAM,IAAI,CAAC,KAAK,EAAE,EAAE;YACpB,UAAU,CAAC,IAAI,EAAE,OAAO,EAAE,CAAC,CAAC,CAAC;YAC7B,CAAC,GAAG,CAAC,CAAC;YACN,OAAO,CAAC,IAAI,CAAC,IAAI,CAAC,CAAC;YACnB,IAAI,GAAG,EAAE,CAAC;YACV,OAAO,CAAC,CAAC,CAAC,GAAG,CAAC,CAAC;SAEf;aAAM;YACN,IAAI,OAAO,GAAG,aAAa,CAAC,CAAC,CAAC,CAAC;YAC/B,IAAI,OAAO,KAAK,SAAS,EAAE;gBAC1B,MAAM,IAAI,KAAK,CAAC,qBAAqB,GAAG,MAAM,CAAC,YAAY,CAAC,CAAC,CAAC,GAAG,GAAG,CAAC,CAAC;aACtE;YAED,IAAM,kBAAkB,GAAG,OAAO,GAAG,EAAE,CAAC;YAExC,OAAO,IAAI,EAAE,CAAC;YACd,KAAK,IAAI,OAAO,IAAI,KAAK,CAAC;YAE1B,IAAI,kBAAkB,EAAE;gBACvB,KAAK,IAAI,CAAC,CAAC;aACX;iBAAM;gBACN,IAAM,YAAY,GAAG,KAAK,GAAG,CAAC,CAAC;gBAC/B,KAAK,MAAM,CAAC,CAAC;gBAEb,IAAI,YAAY,EAAE;oBACjB,KAAK,GAAG,KAAK,KAAK,CAAC,GAAG,CAAC,UAAU,GAAG,CAAC,KAAK,CAAC;iBAC3C;gBAED,OAAO,CAAC,CAAC,CAAC,IAAI,KAAK,CAAC;gBACpB,CAAC,EAAE,CAAC;gBACJ,KAAK,GAAG,KAAK,GAAG,CAAC,CAAC;aAClB;SACD;KACD;IAED,UAAU,CAAC,IAAI,EAAE,OAAO,EAAE,CAAC,CAAC,CAAC;IAC7B,OAAO,CAAC,IAAI,CAAC,IAAI,CAAC,CAAC;IAEnB,OAAO,OAAO,CAAC;AAChB,CAAC;AAED,SAAS,UAAU,CAAC,IAAwB,EAAE,OAAyB,EAAE,CAAS;;;;;;;;IAQjF,IAAI,CAAC,KAAK,CAAC;QAAE,IAAI,CAAC,IAAI,CAAC,CAAC,OAAO,CAAC,CAAC,CAAC,EAAE,OAAO,CAAC,CAAC,CAAC,EAAE,OAAO,CAAC,CAAC,CAAC,EAAE,OAAO,CAAC,CAAC,CAAC,CAAC,CAAC,CAAC;SACpE,IAAI,CAAC,KAAK,CAAC;QAAE,IAAI,CAAC,IAAI,CAAC,CAAC,OAAO,CAAC,CAAC,CAAC,EAAE,OAAO,CAAC,CAAC,CAAC,EAAE,OAAO,CAAC,CAAC,CAAC,EAAE,OAAO,CAAC,CAAC,CAAC,EAAE,OAAO,CAAC,CAAC,CAAC,CAAC,CAAC,CAAC;SACrF,IAAI,CAAC,KAAK,CAAC;QAAE,IAAI,CAAC,IAAI,CAAC,CAAC,OAAO,CAAC,CAAC,CAAC,CAAC,CAAC,CAAC;AAC3C,CAAC;SAEe,MAAM,CAAC,OAA0B;IAChD,IAAI,eAAe,GAAG,CAAC,CAAC;IACxB,IAAI,cAAc,GAAG,CAAC,CAAC;IACvB,IAAI,gBAAgB,GAAG,CAAC,CAAC;IACzB,IAAI,SAAS,GAAG,CAAC,CAAC;IAClB,IAAI,QAAQ,GAAG,EAAE,CAAC;IAElB,KAAK,IAAI,CAAC,GAAG,CAAC,EAAE,CAAC,GAAG,OAAO,CAAC,MAAM,EAAE,CAAC,EAAE,EAAE;QACxC,IAAM,IAAI,GAAG,OAAO,CAAC,CAAC,CAAC,CAAC;QACxB,IAAI,CAAC,GAAG,CAAC;YAAE,QAAQ,IAAI,GAAG,CAAC;QAC3B,IAAI,IAAI,CAAC,MAAM,KAAK,CAAC;YAAE,SAAS;QAEhC,IAAI,mBAAmB,GAAG,CAAC,CAAC;QAE5B,IAAM,YAAY,GAAa,EAAE,CAAC;QAElC,KAAsB,UAAI,EAAJ,aAAI,EAAJ,kBAAI,EAAJ,IAAI,EAAE;YAAvB,IAAM,OAAO,aAAA;YACjB,IAAI,eAAe,GAAG,aAAa,CAAC,OAAO,CAAC,CAAC,CAAC,GAAG,mBAAmB,CAAC,CAAC;YACtE,mBAAmB,GAAG,OAAO,CAAC,CAAC,CAAC,CAAC;YAEjC,IAAI,OAAO,CAAC,MAAM,GAAG,CAAC,EAAE;gBACvB,eAAe;oBACd,aAAa,CAAC,OAAO,CAAC,CAAC,CAAC,GAAG,eAAe,CAAC;wBAC3C,aAAa,CAAC,OAAO,CAAC,CAAC,CAAC,GAAG,cAAc,CAAC;wBAC1C,aAAa,CAAC,OAAO,CAAC,CAAC,CAAC,GAAG,gBAAgB,CAAC,CAAC;gBAE9C,eAAe,GAAG,OAAO,CAAC,CAAC,CAAC,CAAC;gBAC7B,cAAc,GAAG,OAAO,CAAC,CAAC,CAAC,CAAC;gBAC5B,gBAAgB,GAAG,OAAO,CAAC,CAAC,CAAC,CAAC;aAC9B;YAED,IAAI,OAAO,CAAC,MAAM,KAAK,CAAC,EAAE;gBACzB,eAAe,IAAI,aAAa,CAAC,OAAO,CAAC,CAAC,CAAC,GAAG,SAAS,CAAC,CAAC;gBACzD,SAAS,GAAG,OAAO,CAAC,CAAC,CAAC,CAAC;aACvB;YAED,YAAY,CAAC,IAAI,CAAC,eAAe,CAAC,CAAC;SACnC;QAED,QAAQ,IAAI,YAAY,CAAC,IAAI,CAAC,GAAG,CAAC,CAAC;KACnC;IAED,OAAO,QAAQ,CAAC;AACjB,CAAC;AAED,SAAS,aAAa,CAAC,GAAW;IACjC,IAAI,MAAM,GAAG,EAAE,CAAC;IAChB,GAAG,GAAG,GAAG,GAAG,CAAC,GAAG,CAAC,CAAC,GAAG,IAAI,CAAC,IAAI,CAAC,GAAG,GAAG,IAAI,CAAC,CAAC;IAC3C,GAAG;QACF,IAAI,OAAO,GAAG,GAAG,GAAG,EAAE,CAAC;QACvB,GAAG,MAAM,CAAC,CAAC;QACX,IAAI,GAAG,GAAG,CAAC,EAAE;YACZ,OAAO,IAAI,EAAE,CAAC;SACd;QACD,MAAM,IAAI,KAAK,CAAC,OAAO,CAAC,CAAC;KACzB,QAAQ,GAAG,GAAG,CAAC,EAAE;IAElB,OAAO,MAAM,CAAC;AACf;;;;"}
+\ No newline at end of file
+diff --git a/node_modules/sourcemap-codec/package.json b/node_modules/sourcemap-codec/package.json
+index 4b2d219..96f5feb 100644
+--- a/node_modules/sourcemap-codec/package.json
++++ b/node_modules/sourcemap-codec/package.json
+@@ -5,6 +5,15 @@
+   "main": "dist/sourcemap-codec.umd.js",
+   "module": "dist/sourcemap-codec.es.js",
+   "types": "dist/types/sourcemap-codec.d.ts",
++  "exports": {
++    ".": {
++      "browser": "./dist/sourcemap-codec.umd.js",
++      "import": "./dist/sourcemap-codec.mjs",
++      "require": "./dist/sourcemap-codec.umd.js"
++    },
++    "./package.json": "./package.json",
++    "./": "./"
++  },
+   "scripts": {
+     "test": "mocha",
+     "build": "rm -rf dist && rollup -c && tsc",
diff --git a/yarn.lock b/yarn.lock
index b556decc2..1138e33b0 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1286,6 +1286,11 @@
     semver "^7.3.2"
     tsutils "^3.17.1"
 
+"@yarnpkg/lockfile@^1.1.0":
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/@yarnpkg/lockfile/-/lockfile-1.1.0.tgz#e77a97fbd345b76d83245edcd17d393b1b41fb31"
+  integrity sha512-GpSwvyXOcOOlV70vbnzjj4fW5xW/FdUF6nQEt1ENy7m4ZCczi1+/buVUPAqmGfqznsORNFzUMjctTIp8a9tuCQ==
+
 JSV@^4.0.2:
   version "4.0.2"
   resolved "https://registry.yarnpkg.com/JSV/-/JSV-4.0.2.tgz#d077f6825571f82132f9dffaed587b4029feff57"
@@ -3914,6 +3919,13 @@ find-yarn-workspace-root2@1.2.16:
     micromatch "^4.0.2"
     pkg-dir "^4.2.0"
 
+find-yarn-workspace-root@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/find-yarn-workspace-root/-/find-yarn-workspace-root-2.0.0.tgz#f47fb8d239c900eb78179aa81b66673eac88f7bd"
+  integrity sha512-1IMnbjt4KzsQfnhnzNd8wUEgXZ44IzZaZmnLYx7D5FZlaHt2gW20Cri8Q+E/t5tIj4+epTBub+2Zxu/vNILzqQ==
+  dependencies:
+    micromatch "^4.0.2"
+
 flat-cache@^3.0.4:
   version "3.0.4"
   resolved "https://registry.yarnpkg.com/flat-cache/-/flat-cache-3.0.4.tgz#61b0338302b2fe9f957dcc32fc2a87f1c3048b11"
@@ -5748,6 +5760,13 @@ kind-of@^6.0.0, kind-of@^6.0.2, kind-of@^6.0.3:
   resolved "https://registry.yarnpkg.com/kind-of/-/kind-of-6.0.3.tgz#07c05034a6c349fa06e24fa35aa76db4580ce4dd"
   integrity sha512-dcS1ul+9tmeD95T+x28/ehLgd9mENa3LsvDTtzm3vyBEO7RPptvAD+t44WVXaUjTBRcrpFeFlC8WCruUR456hw==
 
+klaw-sync@^6.0.0:
+  version "6.0.0"
+  resolved "https://registry.yarnpkg.com/klaw-sync/-/klaw-sync-6.0.0.tgz#1fd2cfd56ebb6250181114f0a581167099c2b28c"
+  integrity sha512-nIeuVSzdCCs6TDPTqI8w1Yre34sSq7AkZ4B3sfOBbI2CgVSB4Du4aLQijFU2+lhAFCwt9+42Hel6lQNIv6AntQ==
+  dependencies:
+    graceful-fs "^4.1.11"
+
 kleur@^3.0.3:
   version "3.0.3"
   resolved "https://registry.yarnpkg.com/kleur/-/kleur-3.0.3.tgz#a79c9ecc86ee1ce3fa6206d1216c501f147fc07e"
@@ -6938,6 +6957,25 @@ password-prompt@^1.0.4:
     ansi-escapes "^3.1.0"
     cross-spawn "^6.0.5"
 
+patch-package@^6.4.7:
+  version "6.4.7"
+  resolved "https://registry.yarnpkg.com/patch-package/-/patch-package-6.4.7.tgz#2282d53c397909a0d9ef92dae3fdeb558382b148"
+  integrity sha512-S0vh/ZEafZ17hbhgqdnpunKDfzHQibQizx9g8yEf5dcVk3KOflOfdufRXQX8CSEkyOQwuM/bNz1GwKvFj54kaQ==
+  dependencies:
+    "@yarnpkg/lockfile" "^1.1.0"
+    chalk "^2.4.2"
+    cross-spawn "^6.0.5"
+    find-yarn-workspace-root "^2.0.0"
+    fs-extra "^7.0.1"
+    is-ci "^2.0.0"
+    klaw-sync "^6.0.0"
+    minimist "^1.2.0"
+    open "^7.4.2"
+    rimraf "^2.6.3"
+    semver "^5.6.0"
+    slash "^2.0.0"
+    tmp "^0.0.33"
+
 path-exists@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/path-exists/-/path-exists-3.0.0.tgz#ce0ebeaa5f78cb18925ea7d810d7b59b010fd515"
@@ -8306,6 +8344,11 @@ sisteransi@^1.0.5:
   resolved "https://registry.yarnpkg.com/sisteransi/-/sisteransi-1.0.5.tgz#134d681297756437cc05ca01370d3a7a571075ed"
   integrity sha512-bLGGlR1QxBcynn2d5YmDX4MGjlZvy2MRBDRNHLJ8VI6l6+9FUiyTFNJ0IveOSP0bcXgVDPRcfGqA0pjaqUpfVg==
 
+slash@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/slash/-/slash-2.0.0.tgz#de552851a1759df3a8f206535442f5ec4ddeab44"
+  integrity sha512-ZYKh3Wh2z1PpEXWr0MpSBZ0V6mZHAQfYevttO11c51CaWjGTaadiKZ+wVt1PbMlDV5qhMFslpZCemhwOK7C89A==
+
 slash@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/slash/-/slash-3.0.0.tgz#6539be870c165adbd5240220dbe361f1bc4d4634"
@@ -8409,7 +8452,7 @@ source-map@^0.7.3, source-map@~0.7.2:
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.7.3.tgz#5302f8169031735226544092e64981f751750383"
   integrity sha512-CkCj6giN3S+n9qrYiBTX5gystlENnRW5jZeNLHpe6aue+SrHcG5VYwujhW9s4dY31mEGsxBDrHR6oI69fTXsaQ==
 
-sourcemap-codec@^1.4.4:
+sourcemap-codec@^1.4.4, sourcemap-codec@^1.4.8:
   version "1.4.8"
   resolved "https://registry.yarnpkg.com/sourcemap-codec/-/sourcemap-codec-1.4.8.tgz#ea804bd94857402e6992d05a38ef1ae35a9ab4c4"
   integrity sha512-9NykojV5Uih4lgo5So5dtw+f0JgJX30KCNI8gwhz2J9A15wD0Ml6tjHKwf6fTSa6fAdVBdZeNOs9eJ71qCk8vA==