verify-action-build: support .cjs and .mjs compiled bundle extensions

The Dockerfile that rebuilds an action's bundle and diff_js only looked
for *.js. Actions bundled with esbuild or rollup often emit dist/index.cjs
(when the source package declares "type": "module" and needs a CommonJS
bundle for the node runner — JustinBeckwith/linkinator-action v2.4.2 is
the current trigger) or dist/index.mjs. For those actions the current
pipeline both skips deleting the published bundle before rebuild (so a
broken build is masked by the leftover file) and reports "No compiled
JavaScript found" because the comparison walks only *.js.

Extend the pre-rebuild delete step and the has_output probe in
build_action.Dockerfile to cover *.js, *.cjs and *.mjs, and factor the
file-collection in diff_js.py into a _collect_compiled_js helper that
scans all three extensions. Add unit tests covering the helper including
nested output directories (e.g. dist/sub/main/index.cjs).

Generated-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: potiuk

utils/tests/verify_action_build/test_diff_js.py

@@ -16,7 +16,7 @@
 # specific language governing permissions and limitations
 # under the License.
 #
-from verify_action_build.diff_js import beautify_js
+from verify_action_build.diff_js import _collect_compiled_js, beautify_js
 
 
 class TestBeautifyJs:
@@ -47,3 +47,32 @@ def test_consistent_output(self):
         result1 = beautify_js(code)
         result2 = beautify_js(code)
         assert result1 == result2
+
+
+class TestCollectCompiledJs:
+    def test_picks_up_js_cjs_mjs(self, tmp_path):
+        (tmp_path / "dist").mkdir()
+        (tmp_path / "dist" / "index.js").write_text("// js\n")
+        (tmp_path / "dist" / "index.cjs").write_text("// cjs\n")
+        (tmp_path / "dist" / "index.mjs").write_text("// mjs\n")
+        (tmp_path / "dist" / "index.cjs.map").write_text("{}\n")
+        (tmp_path / "dist" / "readme.md").write_text("ignored\n")
+
+        found = _collect_compiled_js(tmp_path)
+
+        from pathlib import Path
+        assert found == {
+            Path("dist/index.js"),
+            Path("dist/index.cjs"),
+            Path("dist/index.mjs"),
+        }
+
+    def test_empty_dir_returns_empty(self, tmp_path):
+        assert _collect_compiled_js(tmp_path) == set()
+
+    def test_nested_dirs(self, tmp_path):
+        (tmp_path / "dist" / "sub" / "main").mkdir(parents=True)
+        (tmp_path / "dist" / "sub" / "main" / "index.cjs").write_text("// cjs\n")
+
+        from pathlib import Path
+        assert _collect_compiled_js(tmp_path) == {Path("dist/sub/main/index.cjs")}

utils/verify_action_build/diff_js.py

@@ -25,6 +25,22 @@
 from .console import console, link
 from .diff_display import show_colored_diff
 
+# Extensions emitted by action build toolchains. `.js` is the common case
+# (webpack/ncc/tsc); `.cjs` is what esbuild/rollup write when the source
+# package is ESM (type: module) and the action needs a CommonJS bundle for
+# the node runner (e.g. JustinBeckwith/linkinator-action);
+# `.mjs` is the inverse — an ESM bundle for node20+ runners.
+COMPILED_JS_EXTENSIONS = ("*.js", "*.cjs", "*.mjs")
+
+
+def _collect_compiled_js(base: Path) -> set[Path]:
+    """Return relative paths of compiled JS files under base."""
+    found: set[Path] = set()
+    for pattern in COMPILED_JS_EXTENSIONS:
+        for f in base.rglob(pattern):
+            found.add(f.relative_to(base))
+    return found
+
 
 def beautify_js(content: str) -> str:
     """Reformat JavaScript for readable diffing."""
@@ -46,13 +62,8 @@ def diff_js_files(
     # Files vendored by @vercel/ncc that are not built from the action's source.
     ignored_files = {"sourcemap-register.js"}
 
-    original_files = set()
-    rebuilt_files = set()
-
-    for f in original_dir.rglob("*.js"):
-        original_files.add(f.relative_to(original_dir))
-    for f in rebuilt_dir.rglob("*.js"):
-        rebuilt_files.add(f.relative_to(rebuilt_dir))
+    original_files = _collect_compiled_js(original_dir)
+    rebuilt_files = _collect_compiled_js(rebuilt_dir)
 
     all_files = sorted(original_files | rebuilt_files)
 

utils/verify_action_build/dockerfiles/build_action.Dockerfile

@@ -83,9 +83,15 @@ RUN if [ -d "node_modules" ]; then \
       mkdir /original-node-modules; \
     fi
 
-# Delete compiled JS from output dir before rebuild to ensure a clean build
+# Delete compiled JS from output dir before rebuild to ensure a clean build.
+# Covers .js, .cjs and .mjs — actions bundled with esbuild/rollup may emit
+# dist/index.cjs (e.g. JustinBeckwith/linkinator-action) or dist/index.mjs.
 RUN OUT_DIR=$(cat /out-dir.txt); \
-    if [ -d "$OUT_DIR" ]; then find "$OUT_DIR" -name '*.js' -print -delete > /deleted-js.log 2>&1; else echo "no $OUT_DIR/ directory" > /deleted-js.log; fi
+    if [ -d "$OUT_DIR" ]; then \
+      find "$OUT_DIR" \( -name '*.js' -o -name '*.cjs' -o -name '*.mjs' \) -print -delete > /deleted-js.log 2>&1; \
+    else \
+      echo "no $OUT_DIR/ directory" > /deleted-js.log; \
+    fi
 
 # If an approved (previous) commit hash is provided, restore the dev-dependency
 # lock files from that commit so the rebuild uses the same toolchain (e.g. same
@@ -179,7 +185,7 @@ RUN BUILD_DIR=$(cat /build-dir.txt); \
 RUN OUT_DIR=$(cat /out-dir.txt); \
     BUILD_DIR=$(cat /build-dir.txt); \
     RUN_CMD=$(cat /run-cmd); \
-    has_output() { [ -d "$OUT_DIR" ] && find "$OUT_DIR" -name '*.js' -print -quit | grep -q .; }; \
+    has_output() { [ -d "$OUT_DIR" ] && find "$OUT_DIR" \( -name '*.js' -o -name '*.cjs' -o -name '*.mjs' \) -print -quit | grep -q .; }; \
     BUILD_DONE=false; \
     if [ -x build ] && ./build dist 2>/dev/null; then \
       echo "build-step: ./build dist" >> /build-info.log; \