Write output to workflow job summary

.pre-commit-config.yaml

@@ -9,6 +9,6 @@ repos:
       - id: mixed-line-ending
       - id: check-added-large-files
   - repo: https://github.com/scop/pre-commit-shfmt
-    rev: v3.4.2-1
+    rev: v3.5.1-1
     hooks:
     - id: shfmt

action.yml

@@ -29,3 +29,20 @@ runs:
     - run: |
         "${{ github.action_path }}/check.sh" "${{ inputs.clang-format-version }}" "${{ inputs.check-path }}" "${{ inputs.fallback-style }}" "${{ inputs.exclude-regex }}"
       shell: bash
+    - name: Save PR head commit SHA
+      if: failure() && github.event_name == 'pull_request'
+      shell: bash
+      run: |
+        SHA="${{ github.event.pull_request.head.sha }}"
+        echo "SHA=$SHA" >> $GITHUB_ENV
+    - name: Save latest commit SHA if not PR
+      if: failure() && github.event_name != 'pull_request'
+      shell: bash
+      run: echo "SHA=${{ github.sha }}" >> $GITHUB_ENV
+
+    - name: Report failure in job summary
+      if: failure()
+      run: |
+        DEEPLINK="https://github.com/${{ github.repository }}/commit/${{ env.SHA }}"
+        echo -e "Format check failed on commit [${GITHUB_SHA:0:8}]($DEEPLINK) with files:\n$(<$GITHUB_WORKSPACE/failing-files.txt)" >> $GITHUB_STEP_SUMMARY
+      shell: bash

check.sh

@@ -20,18 +20,22 @@
 format_diff() {
 	local filepath="$1"
 	# Invoke clang-format with dry run and formatting error output
-	if [[ "$CLANG_FORMAT_VERSION" -gt "9" ]]; then
+	if [[ $CLANG_FORMAT_VERSION -gt "9" ]]; then
 		local_format="$(docker run -i -v "$(pwd)":"$(pwd)" -w "$(pwd)" ghcr.io/jidicula/clang-format:"$CLANG_FORMAT_VERSION" -n --Werror --style=file --fallback-style="$FALLBACK_STYLE" "${filepath}")"
-	else
+	else # Versions below 9 don't have dry run
 		formatted="$(docker run -i -v "$(pwd)":"$(pwd)" -w "$(pwd)" ghcr.io/jidicula/clang-format:"$CLANG_FORMAT_VERSION" --style=file --fallback-style="$FALLBACK_STYLE" "${filepath}")"
 		local_format="$(diff -q <(cat "${filepath}") <(echo "${formatted}"))"
 	fi
 
 	local format_status="$?"
-	if [[ "${format_status}" -ne 0 ]]; then
-		echo "Failed on file: $filepath"
+	if [[ ${format_status} -ne 0 ]]; then
+		# Append Markdown-bulleted monospaced filepath of failing file to
+		# summary file.
+		echo "* \`$filepath\`" >>failing-files.txt
+
+		echo "Failed on file: $filepath" >&2
 		echo "$local_format" >&2
-		exit_code=1
+		exit_code=1 # flip the global exit code
 		return "${format_status}"
 	fi
 	return 0
@@ -49,8 +53,8 @@ fi
 
 cd "$GITHUB_WORKSPACE" || exit 2
 
-if [[ ! -d "$CHECK_PATH" ]]; then
-	echo "Not a directory in the workspace, fallback to all files."
+if [[ ! -d $CHECK_PATH ]]; then
+	echo "Not a directory in the workspace, fallback to all files." >&2
 	CHECK_PATH="."
 fi
 
@@ -68,9 +72,11 @@ src_files=$(find "$CHECK_PATH" -name .git -prune -o -regextype posix-egrep -rege
 # check formatting in each source file
 for file in $src_files; do
 	# Only check formatting if the path doesn't match the regex
-	if ! [[ "${file}" =~ $EXCLUDE_REGEX ]]; then
+	if ! [[ ${file} =~ $EXCLUDE_REGEX ]]; then
 		format_diff "${file}"
 	fi
 done
 
+# global exit code is flipped to nonzero if any invocation of `format_diff` has
+# a formatting difference.
 exit "$exit_code"