Early exit when no files are changed.

__tests__/main.test.ts

@@ -47,6 +47,47 @@ describe('run', () => {
     expect(addLabelsMock).toHaveBeenCalledTimes(0);
   });
 
+  it('does not add labels to PRs that have no changed files', async () => {
+    usingLabelerConfigYaml('only_pdfs.yml');
+    mockGitHubResponseChangedFiles();
+
+    await run();
+
+    expect(removeLabelMock).toHaveBeenCalledTimes(0);
+    expect(addLabelsMock).toHaveBeenCalledTimes(0);
+  });
+
+  it('(with sync-labels: true) removes all labels from PRs that have no changed files', async () => {
+    let mockInput = {
+      'repo-token': 'foo',
+      'configuration-path': 'bar',
+      'sync-labels': true
+    };
+
+    jest
+      .spyOn(core, 'getInput')
+      .mockImplementation((name: string, ...opts) => mockInput[name]);
+
+    usingLabelerConfigYaml('only_pdfs.yml');
+    mockGitHubResponseChangedFiles();
+    getPullMock.mockResolvedValue(<any>{
+      data: {
+        labels: [{name: 'touched-a-pdf-file'}]
+      }
+    });
+
+    await run();
+
+    expect(removeLabelMock).toHaveBeenCalledTimes(1);
+    expect(addLabelsMock).toHaveBeenCalledTimes(0);
+    expect(removeLabelMock).toHaveBeenCalledWith({
+      owner: 'monalisa',
+      repo: 'helloworld',
+      issue_number: 123,
+      name: 'touched-a-pdf-file'
+    });
+  });
+
   it('(with sync-labels: true) it deletes preexisting PR labels that no longer match the glob pattern', async () => {
     let mockInput = {
       'repo-token': 'foo',

dist/index.js

@@ -66,6 +66,18 @@ function run() {
             const labelGlobs = yield getLabelGlobs(client, configPath);
             const labels = [];
             const labelsToRemove = [];
+            if (!changedFiles.length) {
+                core.debug(`exiting early because pr #${prNumber} has no changed files.`);
+                if (syncLabels) {
+                    for (let label of pullRequest.labels) {
+                        if (label.name) {
+                            labelsToRemove.push(label.name);
+                        }
+                    }
+                    yield removeLabels(client, prNumber, labelsToRemove);
+                }
+                return;
+            }
             for (const [label, globs] of labelGlobs.entries()) {
                 core.debug(`processing ${label}`);
                 if (checkGlobs(changedFiles, globs)) {

src/labeler.ts

@@ -40,6 +40,23 @@ export async function run() {
 
     const labels: string[] = [];
     const labelsToRemove: string[] = [];
+
+    if (!changedFiles.length) {
+      core.debug(`exiting early because pr #${prNumber} has no changed files.`);
+
+      if (syncLabels) {
+        for (let label of pullRequest.labels) {
+          if (label.name) {
+            labelsToRemove.push(label.name);
+          }
+        }
+
+        await removeLabels(client, prNumber, labelsToRemove);
+      }
+
+      return;
+    }
+
     for (const [label, globs] of labelGlobs.entries()) {
       core.debug(`processing ${label}`);
       if (checkGlobs(changedFiles, globs)) {