TLDR

Regression since Mill 1.0.3: Mill calls runner.tasks(...) during scheduler pre-filtering in the Mill/Zinc worker, before the forked test JVM is launched. For Weaver, runner.tasks(...) initializes GlobalResource, so forkEnv is not visible there.

Then the queue scheduler calls runner.tasks(...) one claimed class at a time, so Weaver's GlobalResource TaskDef and resource-using suite TaskDef are split apart.

Minimal repro: https://github.com/nguyenyou/mill-weaver-forkenv-global-resource-repro

Root Cause

Current path:

TestModuleUtil.runTests
  |
  |-- ZincOp.GetTestTasks
  |     |
  |     `-- TestRunnerUtils.getTestTasks0
  |           |
  |           `-- runner.tasks(...)   // runs in Mill/Zinc worker, no forkEnv
  |
  `-- forked test JVM
        |
        `-- queue scheduler calls runner.tasks([one claimed class])

For most frameworks, runner.tasks(...) is effectively cheap task materialization. For Weaver, it is semantically meaningful: global resources are collected and initialized from the full TaskDef batch.

So there are two related scheduler issues:

1. runner.tasks(...) runs outside the forked JVM, so framework setup cannot see forkEnv.
2. The queue scheduler splits related TaskDefs, so Weaver sees the suite without the global resource.

Regression / Affected Versions

Bisect points to:

• PR: Consolidate old TestModuleUtil#runTestDefault code path into runTestQueueScheduler #5630
• Commit: 628e766d2d1085846ee5b6447199da97edeaaa0a
• Commit title: Consolidate old TestModuleUtil#runTestDefault code path into runTestQueueScheduler

First affected stable release: Mill 1.0.3

Affected:

• 1.0.3+
• all current 1.1.x releases, including 1.1.5

Not affected:

• 0.12.x
• 1.0.0 through 1.0.2

User report: 0.12.16 works, 1.1.5 fails.

Expected

Framework setup and TaskDef batching should happen inside the forked test JVM with forkEnv applied, or Mill should preserve full selected TaskDef batch semantics for frameworks that require it.

Actual

Mill pre-filters by invoking framework task creation in a worker without forkEnv, then the forked queue runner invokes framework task creation per claimed class.