ci: skip CJS api-extractor checks on PR builds

[frankmueller-msft]

Summary

Skip redundant CJS api-extractor invocations on PR builds to reduce build time. CJS entry point files are byte-for-byte identical to ESM — full CJS checks run on main/release CI where correctness matters.

Measured impact: Build Stage dropped from 18m40s to 16m18s (~2m20s wall-clock improvement).

What changes on PR builds

When SKIP_CJS_CHECKS=true (set automatically for PR builds):

• api-extractor:commonjs removed from build:test, build:test:cjs, api dependency arrays (~65 invocations, ~6 min CPU)
• check:exports becomes a no-op — the package's concurrently script would fail without CJS entry points (~159 invocations, ~16 min CPU)
• check:are-the-types-wrong becomes a no-op — attw checks CJS+ESM type resolution
• AreTheTypesWrong pipeline job excluded from PR runs (runs via pnpm, not fluid-build)

What does NOT change

• Non-PR builds (main, release branches) run full CJS+ESM checks exactly as before
• No package.json modifications — all packages keep existing scripts
• No config file deletions — api-extractor-lint-*.cjs.json files stay
• Local npm run build is unaffected (env var not set)

Files changed

File	What
fluidBuild.config.cjs	Conditional ternaries for api, build:test, build:test:cjs, check:exports, check:are-the-types-wrong based on SKIP_CJS_CHECKS env var
tools/pipelines/templates/include-vars.yml	Add skipCjsChecks pipeline variable (true on PR builds)
tools/pipelines/templates/include-build-lint.yml	Pass SKIP_CJS_CHECKS env var to ci:build and lint steps
tools/pipelines/build-client.yml	Conditionally exclude AreTheTypesWrong job on PR builds

Test plan

• PR CI passes — all checks green
• Build Stage Build: 16m18s (vs 18m40s baseline)
• Verify main CI still runs full CJS checks after merge

Closes #26592

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR reduces CI time on Pull Request builds by skipping redundant CommonJS api-extractor validation tasks when CJS entrypoints are identical to ESM, while keeping full checks on main/release branches.

Changes:

• Add PR-only pipeline variable skipCjsChecks and pass it as SKIP_CJS_CHECKS to build/lint steps.
• Update fluidBuild.config.cjs to conditionally remove api-extractor:commonjs from key dependency chains when SKIP_CJS_CHECKS is enabled.
• Override check:exports behavior under SKIP_CJS_CHECKS to run ESM-only export-check subtasks.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
fluidBuild.config.cjs	Adds SKIP_CJS_CHECKS gating to omit CJS api-extractor tasks and alters check:exports execution plan on PR builds.
tools/pipelines/templates/include-vars.yml	Introduces skipCjsChecks variable (true on PR builds).
tools/pipelines/templates/include-build-lint.yml	Passes SKIP_CJS_CHECKS into ci:build and lint pipeline steps.

[Copilot]

skipCjsChecks is derived via a strict process.env.SKIP_CJS_CHECKS === "true" check. In Azure Pipelines, boolean variables commonly come through as "True"/"False" (capitalized), so PR builds may not actually enable the skip behavior. Consider normalizing (e.g. case-insensitive) and/or accepting "1" to make the gate reliable.

Suggested change

	const skipCjsChecks = process.env.SKIP_CJS_CHECKS === "true";
	const skipCjsChecks =
	typeof process.env.SKIP_CJS_CHECKS === "string" &&
	(process.env.SKIP_CJS_CHECKS.toLowerCase() === "true" || process.env.SKIP_CJS_CHECKS === "1");

[frankmueller-msft]

Not an issue — the pipeline variable uses ${{ lower(eq(variables['Build.Reason'], 'PullRequest')) }} in include-vars.yml, which outputs lowercase "true" / "false". The === "true" check matches correctly.

[Copilot]

When skipCjsChecks is enabled, check:exports becomes a non-script task that only depends on a hard-coded list of check:exports:esm:* subtasks. This skips packages whose check:exports script isn’t implemented via those subtasks (e.g. @fluid-internal/devtools-view runs api-extractor directly and has no check:exports:esm:* scripts), reducing PR validation unintentionally. Consider preserving per-package check:exports execution while making the CJS subtasks no-ops (or otherwise filtered) so nonstandard packages still get checked.

[frankmueller-msft]

Correct that check:exports is fully disabled, not just the CJS subtasks. This is intentional — there's no clean way to skip only CJS subtasks because:

1. 88 packages use concurrently "npm:check:exports:*" which glob-matches both CJS and ESM subtasks. Concurrently runs via npm, not fluid-build, so fluid-build task overrides can't selectively suppress the CJS subtask invocations.
2. Fluid-build's script field is boolean (true/false) — no custom command override to substitute e.g. concurrently "npm:check:exports:esm:*".
3. Only 2 packages use direct api-extractor instead of concurrently (devtools-view, example-utils), and both have typeValidation: { disabled: true }.

Full check:exports validation (CJS + ESM) runs on main/release CI. The PR-only skip is a deliberate tradeoff: ~2 min wall-clock savings vs deferred ESM export lint to merge time.