## Summary
Fixes a bug where the `Bun.build()` API with `compile: true` did not
properly apply sourcemaps, even when `sourcemap: "inline"` was
specified. This resulted in error stack traces showing bundled virtual
paths (`/$bunfs/root/`) instead of actual source file names and line
numbers.
## Problem
The CLI `bun build --compile --sourcemap` worked correctly, but the
equivalent API call did not:
```javascript
// This did NOT work (before fix)
await Bun.build({
entrypoints: ['./app.js'],
compile: true,
sourcemap: "inline" // <-- Was ignored/broken
});
```
Error output showed bundled paths:
```
error: Error from helper module
at helperFunction (/$bunfs/root/app.js:4:9) // ❌ Wrong path
at main (/$bunfs/root/app.js:9:17) // ❌ Wrong line numbers
```
## Root Cause
The CLI explicitly overrides any sourcemap type to `.external` when
compile mode is enabled (in `/workspace/bun/src/cli/Arguments.zig`):
```zig
// when using --compile, only `external` works
if (ctx.bundler_options.compile) {
opts.source_map = .external;
}
```
The API implementation in `JSBundler.zig` was missing this override.
## Solution
Added the same sourcemap override logic to `JSBundler.zig` when compile
mode is enabled:
```zig
// When using --compile, only `external` sourcemaps work, as we do not
// look at the source map comment. Override any other sourcemap type.
if (this.source_map != .none) {
this.source_map = .external;
}
```
Now error output correctly shows source file names:
```
error: Error from helper module
at helperFunction (helper.js:2:9) // ✅ Correct file
at main (app.js:4:3) // ✅ Correct line numbers
```
## Tests
Added comprehensive test coverage in
`/workspace/bun/test/bundler/bun-build-compile-sourcemap.test.ts`:
- ✅ `sourcemap: "inline"` works
- ✅ `sourcemap: true` works
- ✅ `sourcemap: "external"` works
- ✅ Multiple source files show correct file names
- ✅ Without sourcemap, bundled paths are shown (expected behavior)
All tests:
- ✅ Fail with `USE_SYSTEM_BUN=1` (confirms bug exists)
- ✅ Pass with `bun bd test` (confirms fix works)
- ✅ Use `tempDir()` to avoid disk space issues
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
