feat(scalajs): Overridable test-time JS env (bunTestJsEnv)#11
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Exposes a new `BunScalaJSTests.bunTestJsEnv: T[Map[String, String]]`
task that feeds the Scala.js test process's environment, and overrides
`jsEnvConfig` inside `BunScalaJSTests` so tests source their env from it.
Defaults to `outer.bunJsEnv()` unchanged — no behavior change for
existing users. Opt-in downstream overrides look like:
object test extends BunScalaJSTests:
override def bunTestJsEnv = Task {
super.bunTestJsEnv() + ("NODE_ENV" -> "production")
}
The motivating case: tests that spin up an in-process `Bun.serve({...})`
want `NODE_ENV=production` so Bun's `development` option defaults to
`false`. Otherwise any fetch-handler Promise rejection gets rewritten
into a ~100 KB HTML `BunError` React-overlay `Response`, and the test
asserts against the overlay HTML instead of the real error — masking
the bug. Giving tests their own env map surfaces those rejections as
proper errors without disturbing `bunRun`/production invocations on
the outer module.
Also adds a CHANGELOG entry documenting the 0.2.1 semantics.
Verified via a downstream `fast-mcp-scala` `publishLocal` round-trip —
a previously-blocked Scala.js HTTP test that POSTs an MCP initialize
request to an in-process `Bun.serve` now passes.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Adds an opt-in hook so downstream Scala.js tests can diverge their process environment from production
bunRunwithout having to rebuild the whole test bridge.BunScalaJSTests.bunTestJsEnv: T[Map[String, String]]— test-scoped override for the Scala.js test process environment.BunScalaJSTests.jsEnvConfigoverride sources itsenvfrombunTestJsEnvso customizing that map is enough to diverge test env.outer.bunJsEnv()unchanged — no behavior change for existing consumers.Why
Tests that spin up an in-process
Bun.serve({...})typically wantNODE_ENV=productionso Bun'sdevelopmentoption defaults tofalse. Otherwise Bun's dev-mode error overlay rewrites any fetch-handler Promise rejection into a ~100 KB HTMLBunErrorReact-overlayResponse. The test then asserts against overlay HTML instead of the real error, which hides real bugs.Downstream opt-in:
Verification
./mill millbun.compileclean./mill millbun.publishLocalpublishescom.tjclp:mill-bun_mill1_3:0.2.1-SNAPSHOT(viaPUBLISH_VERSIONenv)initializeagainstBun.servenow passes onceNODE_ENV=productionis injected via the new hook.Follow-up
Suitable for a 0.2.1 patch release. CHANGELOG entry included.
🤖 Generated with Claude Code