fix: resolve Docker performance issues on Windows#17
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…Windows The - .:/app bind-mount crosses the WSL2<->Windows filesystem boundary on every source file read (the Elixir compiler reads all .ex files on recompile), causing significant latency. Replace it with Docker Compose develop.watch, which syncs changed files via Docker's internal protocol, bypassing the slow bridge entirely. - Dockerfile.dev: add COPY . . to bake initial source into the image layer - docker-compose.dev.yml: remove .:/app bind-mount, add develop.watch for lib/ config/ priv/ test/ assets/ with rebuild triggers on mix.exs/mix.lock - .dockerignore: add .worktrees/ exclusion; clarify test/ is synced at runtime New workflow: `docker compose -f docker-compose.dev.yml watch`
Two root causes of sluggish page loads in Docker on Windows: 1. BEAM busy-wait: idle schedulers spin on vCPUs by default, starving each other in WSL2's shared VM. ERL_FLAGS +sbwt none disables spinning so schedulers sleep immediately when idle, reducing per-request latency. 2. enable_expensive_runtime_checks: LiveView validates assigns, slots, and other invariants on every render. In a constrained container environment this is noticeably slow. PHX_EXPENSIVE_CHECKS=false disables it in Docker while native dev keeps it on (env var defaults to "true").
…before server develop.watch was syncing priv/ from the Windows host into the container, overwriting freshly-compiled Tailwind/esbuild output with stale host files. Exclude priv/static/assets/ from the sync so the container's own build is authoritative. Add mix assets.build to the startup sequence so CSS/JS are ready before the first request rather than racing the watcher's initial build. Fix .gitattributes to enforce LF for .husky/* so git on Windows no longer checks out the pre-commit hook with CRLF, which causes Exec format error in bash. This unblocks all future commits without --no-verify.
heroicons SVGs are installed to assets/vendor/ by a mix task from the heroicons dependency. With the bind-mount those files came from the Windows host; with COPY . . they must be generated at container startup. Also add #!/bin/sh shebang to pre-commit hook — the real fix for Exec format error on Windows. Without a shebang git tries to exec the file as a binary and fails; with one, sh is invoked which handles the script correctly. eol=lf in .gitattributes does not override core.autocrlf=true on checkout.
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Summary
- .:/appbind-mount crossed the WSL2↔Windows filesystem bridge on every source file read. Source is baked into the image viaCOPY . .; changes synced via Docker's internal protocol.ERL_FLAGS: "+sbwt none +sbwtdcpu none +sbwtdio none"disables scheduler busy-waiting that starved threads in WSL2, reducing per-request latency.PHX_EXPENSIVE_CHECKS=falseturns off assign/slot validation on every render (native dev keeps them on).priv/static/assets/from sync so Tailwind/esbuild output isn't overwritten by stale host files. Addedmix assets.buildbefore server start.mix assets.vendorto startup — installs heroicons SVGs previously from host bind-mount.#!/bin/shshebang (root cause of Exec format error) and.husky/* text eol=lfin.gitattributes.New workflow
```bash
docker compose -f docker-compose.dev.yml build --no-cache
docker compose -f docker-compose.dev.yml watch
```
Test plan