Add nonmatching files to action output.

.github/workflows/e2e.yml

@@ -56,6 +56,29 @@ jobs:
             * @fakeorg/faketeam
             * @${{ github.event.pull_request.user.login }}
 
+      - name: Test Local Action Where No Approvers Match
+        id: no_matching
+        uses: ./
+        continue-on-error: true
+        with:
+          always-succeed-before-approval: false
+          codeowners-path: .github/workflows/E2E_NONMATCHING_CODEOWNERS
+
+      - name: Fail if current_approver_is_not_owner succeeded
+        if: steps.no_matching.outcome == 'success'
+        run: |
+          echo "Error: current_approver_is_not_owner should have failed but succeeded" && exit 1
+
+      - name: Fail if files-missing-approver is not an array of strings
+        run: |
+          echo '${{ steps.no_matching.outputs.files-missing-approver }}' | jq -e 'map(select(type == "string"))' > /dev/null
+
+      - name: Fail if files-missing-approver is not an array longer than 0
+        run: |
+          if [ ! "$(echo '${{ steps.no_matching.outputs.files-missing-approver }}' | jq 'length')" -gt 0 ]; then
+            echo "Error: files-missing-approver should be an array longer than 0" && exit 1
+          fi
+
   test-action-pr-review:
     name: E2E Action Tests PR Review Event
     runs-on: ubuntu-latest
@@ -75,15 +98,3 @@ jobs:
           codeowners-contents: |
             * @fakeorg/faketeam
             * @${{ github.event.review.user.login }}
-
-      - name: Test Local Action Where Current Approver is Not Owner
-        id: current_approver_is_not_owner
-        uses: ./
-        continue-on-error: true
-        with:
-          codeowners-path: .github/workflows/E2E_NONMATCHING_CODEOWNERS
-
-      - name: Fail if current_approver_is_not_owner succeeded
-        if: steps.current_approver_is_not_owner.outcome == 'success'
-        run: |
-          echo "Error: current_approver_is_not_owner should have failed but succeeded" && exit 1

__tests__/main.test.ts

@@ -984,4 +984,157 @@ describe('main.ts', () => {
       expect(createCommitStatus).not.toHaveBeenCalled()
     })
   })
+
+  describe('files-missing-approver output', () => {
+    it('sets output to an empty array when the check passes', async () => {
+      gh.getOctokit.mockReturnValue(
+        gh.buildMockOctokit({
+          listReviews: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: [{ user: { login: 'frontend-dev' }, state: 'APPROVED' }]
+          }),
+          listFiles: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: [{ filename: 'src/app.ts' }]
+          }),
+          getContent: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: { content: b64('*.ts @frontend-dev\n'), encoding: 'base64' }
+          })
+        })
+      )
+
+      await run()
+
+      expect(core.setOutput).toHaveBeenCalledWith(
+        'files-missing-approver',
+        JSON.stringify([])
+      )
+    })
+
+    it('sets output to the list of failing files when the check fails', async () => {
+      gh.getOctokit.mockReturnValue(
+        gh.buildMockOctokit({
+          listReviews: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: [{ user: { login: 'bob' }, state: 'APPROVED' }]
+          }),
+          listFiles: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: [{ filename: 'src/app.ts' }, { filename: 'src/utils.ts' }]
+          }),
+          getContent: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: {
+              content: b64(BASE_CODEOWNERS),
+              encoding: 'base64'
+            }
+          })
+        })
+      )
+
+      await run()
+
+      expect(core.setFailed).toHaveBeenCalled()
+      expect(core.setOutput).toHaveBeenCalledWith(
+        'files-missing-approver',
+        JSON.stringify(['src/app.ts', 'src/utils.ts'])
+      )
+    })
+
+    it('sets output to an empty array when not a pull request event', async () => {
+      gh.context.payload = {}
+      gh.getOctokit.mockReturnValue(gh.buildMockOctokit())
+
+      await run()
+
+      expect(core.setOutput).toHaveBeenCalledWith(
+        'files-missing-approver',
+        JSON.stringify([])
+      )
+    })
+
+    it('sets output to an empty array when skipping due to no approvals', async () => {
+      gh.getOctokit.mockReturnValue(
+        gh.buildMockOctokit({
+          listReviews: jest
+            .fn<() => Promise<unknown>>()
+            .mockResolvedValue({ data: [] })
+        })
+      )
+
+      await run()
+
+      expect(core.setOutput).toHaveBeenCalledWith(
+        'files-missing-approver',
+        JSON.stringify([])
+      )
+    })
+
+    it('sets output to an empty array when author is in ignore-authors', async () => {
+      core.getInput.mockImplementation((name: string) => {
+        if (name === 'github-token') return 'fake-token'
+        if (name === 'ignore-authors') return 'alice'
+        return ''
+      })
+
+      gh.getOctokit.mockReturnValue(
+        gh.buildMockOctokit({
+          listReviews: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: [{ user: { login: 'bob' }, state: 'APPROVED' }]
+          })
+        })
+      )
+
+      await run()
+
+      expect(core.setOutput).toHaveBeenCalledWith(
+        'files-missing-approver',
+        JSON.stringify([])
+      )
+    })
+
+    it('sets output to an empty array when all changed files are ignored', async () => {
+      core.getInput.mockImplementation((name: string) => {
+        if (name === 'github-token') return 'fake-token'
+        if (name === 'ignore-filepaths') return 'dist/**'
+        return ''
+      })
+
+      gh.getOctokit.mockReturnValue(
+        gh.buildMockOctokit({
+          listReviews: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: [{ user: { login: 'bob' }, state: 'APPROVED' }]
+          }),
+          listFiles: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: [{ filename: 'dist/bundle.js' }]
+          })
+        })
+      )
+
+      await run()
+
+      expect(core.setOutput).toHaveBeenCalledWith(
+        'files-missing-approver',
+        JSON.stringify([])
+      )
+    })
+
+    it('sets output to an empty array when the CODEOWNERS file is empty', async () => {
+      gh.getOctokit.mockReturnValue(
+        gh.buildMockOctokit({
+          listReviews: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: [{ user: { login: 'bob' }, state: 'APPROVED' }]
+          }),
+          listFiles: jest.fn<() => Promise<unknown>>().mockResolvedValue({
+            data: [{ filename: 'src/foo.ts' }]
+          }),
+          getContent: jest
+            .fn<() => Promise<unknown>>()
+            .mockResolvedValue({ data: { content: '', encoding: 'base64' } })
+        })
+      )
+
+      await run()
+
+      expect(core.setOutput).toHaveBeenCalledWith(
+        'files-missing-approver',
+        JSON.stringify([])
+      )
+    })
+  })
 })

action.yml

@@ -58,6 +58,13 @@ inputs:
     required: false
     default: ''
 
+outputs:
+  files-missing-approver:
+    description: >-
+      JSON-encoded array of file paths that are missing a required approver. Use
+      fromJSON() in expressions to parse the value. Returns an empty array when
+      all files have required approvals or the check was skipped entirely.
+
 runs:
   using: node24
   main: dist/index.js

src/main.ts

@@ -88,6 +88,7 @@ export async function run(): Promise<void> {
 
     if (!context.payload.pull_request) {
       core.info('Not a pull request event — skipping CODEOWNERS check.')
+      core.setOutput('files-missing-approver', JSON.stringify([]))
       return
     }
 
@@ -133,6 +134,7 @@ export async function run(): Promise<void> {
     if (approvers.size === 0) {
       if (alwaysSucceedBeforeApproval) {
         core.info('No approvals found — skipping CODEOWNERS check.')
+        core.setOutput('files-missing-approver', JSON.stringify([]))
         return
       }
       core.debug(
@@ -147,6 +149,7 @@ export async function run(): Promise<void> {
       core.info(
         `Author "${prAuthor}" is in ignore-authors — CODEOWNERS check passes.`
       )
+      core.setOutput('files-missing-approver', JSON.stringify([]))
       await setCommitStatus(
         octokit,
         owner,
@@ -182,6 +185,7 @@ export async function run(): Promise<void> {
       core.info(
         'All changed files are in ignore-filepaths — CODEOWNERS check passes.'
       )
+      core.setOutput('files-missing-approver', JSON.stringify([]))
       await setCommitStatus(
         octokit,
         owner,
@@ -227,6 +231,7 @@ export async function run(): Promise<void> {
         }
         if (!data.content) {
           core.info('CODEOWNERS file is empty — CODEOWNERS check passes.')
+          core.setOutput('files-missing-approver', JSON.stringify([]))
           await setCommitStatus(
             octokit,
             owner,
@@ -348,6 +353,10 @@ export async function run(): Promise<void> {
         ({ file, requiredOwners }) =>
           `  ${file}: requires approval from ${requiredOwners.join(' or ')}`
       )
+      core.setOutput(
+        'files-missing-approver',
+        JSON.stringify(failures.map(({ file }) => file))
+      )
       core.setFailed(
         `CODEOWNERS check failed. The following files need approval:\n${lines.join('\n')}`
       )
@@ -361,6 +370,7 @@ export async function run(): Promise<void> {
         'CODEOWNERS check failed'
       )
     } else {
+      core.setOutput('files-missing-approver', JSON.stringify([]))
       core.info('CODEOWNERS check passed.')
       await setCommitStatus(
         octokit,