feat: add auto-precompile input to the reusable test workflows

[ChrisRackauckas-Claude]

Note

Draft — please ignore until reviewed by @ChrisRackauckas.

Problem

A job that calls a reusable workflow with uses: may not carry an env: map. GitHub's schema allows only name, uses, with, secrets, needs, if, and permissions there. Adding env: doesn't just get ignored — it makes the whole workflow file invalid, so GitHub creates zero jobs for it and reports a bare startup failure.

That is exactly what happened in SciML/ModelingToolkit.jl#4867, which tried to set JULIA_PKG_PRECOMPILE_AUTO: "0" at the call sites of grouped-tests.yml and sublibrary-project-tests.yml:

$ actionlint .github/workflows/Tests.yml .github/workflows/SublibraryCI.yml
.github/workflows/Tests.yml:30:5: when a reusable workflow is called with "uses", "env" is not available.
  only following keys are allowed: "name", "uses", "with", "secrets", "needs", "if", and "permissions" in job "tests" [syntax-check]
.github/workflows/SublibraryCI.yml:27:5: ... in job "sublibrary-ci" [syntax-check]

The result on that PR: no Tests and no Sublibrary CI checks at all, just two runs listed by file path with no jobs ("This run likely failed because of a workflow file issue"). There is currently no supported way for a consumer to control this env var.

Change

Expose it as an input instead.

• tests.yml — new boolean input auto-precompile (default true), applied as a job-level env: so it covers julia-buildpkg's instantiate/build as well as the julia-runtest step:

  env:
    JULIA_PKG_PRECOMPILE_AUTO: "${{ inputs.auto-precompile && '1' || '0' }}"

• grouped-tests.yml — same input, forwarded to the root-matrix test job.
• sublibrary-project-tests.yml — same input, forwarded from all four shard jobs.

Default true is Pkg's normal behavior, so this is a no-op for every existing consumer. Setting auto-precompile: false defers compilation to load time in the test process, which is the escape hatch for dependency trees that OOM the 4vCPU/8GB runners during Pkg's eager parallel precompilation.

Testing

$ actionlint .github/workflows/*.yml
(exit 0)

$ julia --project=. test/runtests.jl
...
Test Summary:                                                 | Pass  Total  Time
auto-precompile input is plumbed to JULIA_PKG_PRECOMPILE_AUTO |    9      9  0.0s

Full suite passes. The new testset asserts the input exists on all three workflows, that tests.yml sets the env var above steps: (job-level, not step-level), and that all four shards forward it. Verified non-vacuous by deleting one shard's forward:

Expression: count("auto-precompile: \${{ inputs.auto-precompile }}", subs) == 4
 Evaluated: 3 == 4

Runic-clean on test/runtests.jl.

Follow-up

v1 only moves when a vX.Y.Z release tag is pushed (major-version-tag.yml), so consumers on @v1 won't see this input until a release is cut. The ModelingToolkit side is being fixed in two steps: drop the invalid env: blocks now to unblock CI, then pass auto-precompile: false once v1 carries this.

Alternative considered

A generic env-vars multiline input piped into $GITHUB_ENV would cover future vars without another PR here, but it's a broader surface for a narrow need. Happy to switch if you'd prefer that shape.

🤖 Generated with Claude Code

https://claude.ai/code/session_0172My4BE5TgvJmuYxkBuvxU