## Summary
Fixes#12548 - TypeScript syntax doesn't work in BunPlugin when using
`loader: 'ts'`
## The Problem
When creating a virtual module with `build.module()` and specifying
`loader: 'ts'`, TypeScript syntax like `import { type TSchema }` would
fail to parse with errors like:
```
error: Expected "}" but found "TSchema"
error: Expected "from" but found "}"
```
The same code worked fine when using `loader: 'tsx'`, indicating the
TypeScript parser wasn't being configured correctly for `.ts` files.
## Root Cause
The bug was caused by an enum value mismatch between C++ and Zig:
### Before (Incorrect)
- **C++ (`headers-handwritten.h`)**: `jsx=0, js=1, ts=2, tsx=3, ...`
- **Zig API (`api/schema.zig`)**: `jsx=1, js=2, ts=3, tsx=4, ...`
- **Zig Internal (`options.zig`)**: `jsx=0, js=1, ts=2, tsx=3, ...`
When a plugin returned `loader: 'ts'`, the C++ code correctly parsed the
string "ts" and set `BunLoaderTypeTS=2`. However, when this value was
passed to Zig's `Bun__transpileVirtualModule` function (which expects
`api.Loader`), the value `2` was interpreted as `api.Loader.js` instead
of `api.Loader.ts`, causing the TypeScript parser to not be enabled.
### Design Context
The codebase has two loader enum systems by design:
- **`api.Loader`**: External API interface used for C++/Zig
communication
- **`options.Loader`**: Internal representation used within Zig
The conversion between them happens via `options.Loader.fromAPI()` and
`.toAPI()` functions. The C++ layer should use `api.Loader` values since
that's what the interface functions expect.
## The Fix
1. **Aligned enum values**: Updated the `BunLoaderType` constants in
`headers-handwritten.h` to match the values in `api/schema.zig`,
ensuring C++ and Zig agree on the enum values
2. **Removed unnecessary assertion**: Removed the assertion that
`plugin_runner` must be non-null for virtual modules, as it's not
actually required for modules created via `build.module()`
3. **Added regression test**: Created comprehensive test in
`test/regression/issue/12548.test.ts` that verifies TypeScript syntax
works correctly with the `'ts'` loader
## Testing
### New Tests Pass
- ✅ `test/regression/issue/12548.test.ts` - 2 tests verifying TypeScript
type imports work with `'ts'` loader
### Existing Tests Still Pass
- ✅ `test/js/bun/plugin/plugins.test.ts` - 28 pass
- ✅ `test/bundler/bundler_plugin.test.ts` - 52 pass
- ✅ `test/bundler/bundler_loader.test.ts` - 27 pass
- ✅ `test/bundler/esbuild/loader.test.ts` - 10 pass
- ✅ `test/bundler/bundler_plugin_chain.test.ts` - 13 pass
### Manual Verification
```javascript
// This now works correctly with loader: 'ts'
Bun.plugin({
setup(build) {
build.module('hi', () => ({
contents: "import { type TSchema } from '@sinclair/typebox'",
loader: 'ts', // ✅ Works now (previously failed)
}))
},
})
```
🤖 Generated with [Claude Code](https://claude.ai/code)
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
