ci: skip CJS api-extractor checks on PR builds

CJS api-extractor output is byte-for-byte identical to ESM. On PR
builds, skip CJS api-extractor invocations (~22 min CPU, ~2 min
wall-clock) and defer CJS-dependent checks to main/release CI.

When SKIP_CJS_CHECKS=true (set for PR builds via pipeline variable):
- api-extractor:commonjs removed from build:test, build:test:cjs, api
- check:exports becomes a no-op (concurrently script would fail
  without CJS entry points)
- check:are-the-types-wrong becomes a no-op (attw checks CJS+ESM)
- AreTheTypesWrong pipeline job excluded from PR runs

Non-PR builds are unaffected — full CJS+ESM checks run as before.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: frankmueller-msft

fluidBuild.config.cjs

@@ -19,6 +19,8 @@ const releaseGroupPackageJsonGlobs = [
 	"tools/markdown-magic/package.json",
 ];
 
+const skipCjsChecks = process.env.SKIP_CJS_CHECKS === "true";
+
 /**
  * The settings in this file configure the Fluid build tools, such as fluid-build and flub. Some settings apply to the
  * whole repo, while others apply only to the client release group.
@@ -90,11 +92,17 @@ module.exports = {
 		// Generic build:test script should be replaced by :esm or :cjs specific versions.
 		// "tsc" would be nice to eliminate from here, but plenty of packages still focus
 		// on CommonJS.
-		"build:test": ["typetests:gen", "tsc", "api-extractor:commonjs", "api-extractor:esnext"],
-		"build:test:cjs": ["typetests:gen", "tsc", "api-extractor:commonjs"],
+		"build:test": skipCjsChecks
+			? ["typetests:gen", "tsc", "api-extractor:esnext"]
+			: ["typetests:gen", "tsc", "api-extractor:commonjs", "api-extractor:esnext"],
+		"build:test:cjs": skipCjsChecks
+			? ["typetests:gen", "tsc"]
+			: ["typetests:gen", "tsc", "api-extractor:commonjs"],
 		"build:test:esm": ["typetests:gen", "build:esnext", "api-extractor:esnext"],
 		"api": {
-			dependsOn: ["api-extractor:commonjs", "api-extractor:esnext"],
+			dependsOn: skipCjsChecks
+				? ["api-extractor:esnext"]
+				: ["api-extractor:commonjs", "api-extractor:esnext"],
 			script: false,
 		},
 		"api-extractor:commonjs": ["tsc"],
@@ -126,12 +134,29 @@ module.exports = {
 			script: true,
 		},
 		"depcruise": [],
-		"check:exports": ["api"],
+		// When skipping CJS checks, skip check:exports entirely. The package's concurrently
+		// script would fail because CJS entry points aren't generated, and forcing
+		// check:exports:bundle-release-tags to run individually surfaces pre-existing
+		// api-extractor lint errors in packages that have disabled check:exports via
+		// "echo skip". All export checks are deferred to main CI.
+		"check:exports": skipCjsChecks
+			? {
+					dependsOn: [],
+					script: false,
+				}
+			: ["api"],
 		"check:exports:bundle-release-tags": ["build:esnext"],
 		// The package's local 'api-extractor-lint.json' may use the entrypoint from either CJS or ESM,
 		// therefore we need to require both before running api-extractor.
 		"check:release-tags": ["tsc", "build:esnext"],
-		"check:are-the-types-wrong": ["tsc", "build:esnext", "api"],
+		// attw packs the package and checks CJS+ESM type resolution. With CJS entry
+		// points missing, it fails. Defer to main CI where api generates both.
+		"check:are-the-types-wrong": skipCjsChecks
+			? {
+					dependsOn: [],
+					script: false,
+				}
+			: ["tsc", "build:esnext", "api"],
 		"check:format": {
 			dependencies: [],
 			script: true,

tools/pipelines/build-client.yml

@@ -220,7 +220,9 @@ extends:
     - { name: "ci:test:jest", jobName: "JestTest" }
     - { name: "ci:test:realsvc:tinylicious", jobName: "RealsvcTinyliciousTest" }
     - { name: "ci:test:stress:tinylicious", jobName: "StressTinyliciousTest" }
-    - { name: "ci:check:are-the-types-wrong", jobName: "AreTheTypesWrong" }
+    # attw checks CJS+ESM type resolution; skip on PRs where CJS api-extractor is skipped
+    - ${{ if ne(variables['Build.Reason'], 'PullRequest') }}:
+      - { name: "ci:check:are-the-types-wrong", jobName: "AreTheTypesWrong" }
     coverageTests:
     - { name: "ci:test:mocha", jobName: "MochaTest" }
     - { name: "ci:test:realsvc:local", jobName: "RealsvcLocalTest" }

tools/pipelines/templates/include-build-lint.yml

@@ -31,6 +31,9 @@ steps:
       # a transitive dependency of browserslist. Without this, the warning fires once
       # per package during builds, producing 100+ identical warnings in build logs.
       BASELINE_BROWSER_MAPPING_IGNORE_OLD_DATA: 1
+      # Skip CJS api-extractor checks on PR builds to reduce build time.
+      # CJS output is byte-for-byte identical to ESM; full CJS checks run on main/release CI.
+      SKIP_CJS_CHECKS: $(skipCjsChecks)
     inputs:
       command: 'custom'
       workingDir: $(Pipeline.Workspace)/${{ parameters.buildDirectory }}
@@ -42,6 +45,7 @@ steps:
     env:
       # Suppress baseline-browser-mapping staleness warnings during lint as well.
       BASELINE_BROWSER_MAPPING_IGNORE_OLD_DATA: 1
+      SKIP_CJS_CHECKS: $(skipCjsChecks)
     inputs:
       command: 'custom'
       workingDir: $(Pipeline.Workspace)/${{ parameters.buildDirectory }}

tools/pipelines/templates/include-vars.yml

@@ -122,6 +122,10 @@ variables:
   value: ${{ ne(variables['Build.Reason'], 'PullRequest') }}
   readonly: true
 
+- name: skipCjsChecks
+  value: ${{ lower(eq(variables['Build.Reason'], 'PullRequest')) }}
+  readonly: true
+
 - template: /tools/pipelines/templates/include-vars-telemetry-generator.yml@self
 
 # The way 1ES pipeline templates determine the default branch of a repository only works for repos hosted in ADO.