input: add Lsp::show_document hook following LSP window/showDocument

crates/ui/src/input/lsp/definitions.rs

@@ -111,7 +111,7 @@ impl InputState {
     pub(crate) fn on_action_go_to_definition(
         &mut self,
         _: &GoToDefinition,
-        _: &mut Window,
+        window: &mut Window,
         cx: &mut Context<Self>,
     ) {
         let offset = self.cursor();
@@ -121,7 +121,7 @@ impl InputState {
             }
 
             if let Some(location) = locations.first().cloned() {
-                self.go_to_definition(&location, cx);
+                self.go_to_definition(&location, window, cx);
             }
         }
     }
@@ -131,7 +131,7 @@ impl InputState {
         &mut self,
         event: &MouseDownEvent,
         offset: usize,
-        _: &mut Window,
+        window: &mut Window,
         cx: &mut Context<InputState>,
     ) -> bool {
         if !event.modifiers.secondary() {
@@ -149,26 +149,42 @@ impl InputState {
             return false;
         };
 
-        self.go_to_definition(&location, cx);
+        self.go_to_definition(&location, window, cx);
 
         true
     }
 
     pub(crate) fn go_to_definition(
         &mut self,
         location: &lsp_types::LocationLink,
+        window: &mut Window,
         cx: &mut Context<Self>,
     ) {
-        if location
+        let external = location
             .target_uri
             .scheme()
             .map(|s| s.as_str() == "https" || s.as_str() == "http")
-            == Some(true)
-        {
+            == Some(true);
+
+        // Give the host a chance to show the document first (window/showDocument),
+        // e.g. to open virtual/external documents (stdlib docs) in an app window.
+        if let Some(handler) = self.lsp.show_document.clone() {
+            let params = lsp_types::ShowDocumentParams {
+                uri: location.target_uri.clone(),
+                external: Some(external),
+                take_focus: Some(true),
+                selection: Some(location.target_selection_range),
+            };
+            if handler(&params, window, cx) {
+                return;
+            }
+        }
+
+        if external {
             cx.open_url(&location.target_uri.to_string());
         } else {
             // Move to the location.
-            let target_range = location.target_range;
+            let target_range = location.target_selection_range;
             let start = self.text.position_to_offset(&target_range.start);
             let end = self.text.position_to_offset(&target_range.end);
 

crates/ui/src/input/lsp/mod.rs

@@ -19,6 +19,18 @@ pub use document_colors::*;
 pub use hover::*;
 pub use semantic_tokens::*;
 
+/// Host hook to show a document when following an LSP location
+/// (Go to Definition), modeled after the `window/showDocument` request.
+///
+/// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#window_showDocument
+///
+/// Called before the built-in behavior. Return `true` if the host has shown
+/// the document (e.g. opened a docs window for a virtual/external URI);
+/// return `false` to fall through to the default handling (`external` URIs
+/// open in the browser, anything else jumps within the current document).
+pub type ShowDocumentHandler =
+    Rc<dyn Fn(&lsp_types::ShowDocumentParams, &mut Window, &mut App) -> bool>;
+
 /// LSP ServerCapabilities
 ///
 /// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#serverCapabilities
@@ -35,6 +47,11 @@ pub struct Lsp {
     pub document_color_provider: Option<Rc<dyn DocumentColorProvider>>,
     /// The range semantic tokens provider.
     pub semantic_tokens_provider: Option<Rc<dyn DocumentRangeSemanticTokensProvider>>,
+    /// Optional host hook to show documents for Go to Definition locations,
+    /// following the `window/showDocument` request (see [`ShowDocumentHandler`]).
+    ///
+    /// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#window_showDocument
+    pub show_document: Option<ShowDocumentHandler>,
 
     document_colors: Vec<(lsp_types::Range, Hsla)>,
     /// Cached semantic tokens as absolute position ranges + theme token-type
@@ -55,6 +72,7 @@ impl Default for Lsp {
             definition_provider: None,
             document_color_provider: None,
             semantic_tokens_provider: None,
+            show_document: None,
             document_colors: vec![],
             semantic_tokens: vec![],
             _hover_task: Task::ready(Ok(())),