Make sure that empty config options don't accidently label things

__tests__/fixtures/not_supported.yml

@@ -0,0 +1,2 @@
+label:
+  - unknown-check: 'this-check-is-not-supported'

__tests__/labeler.test.ts

@@ -17,17 +17,18 @@ describe('toMatchConfig', () => {
       'head-branch': ['testing-head'],
       'base-branch': ['testing-base']
     };
+    const expected: MatchConfig = {
+      changedFiles: {
+        all: ['testing-all'],
+        any: ['testing-any']
+      },
+      headBranch: ['testing-head'],
+      baseBranch: ['testing-base']
+    };
 
     it('returns a MatchConfig object with all options', () => {
       const result = toMatchConfig(config);
-      expect(result).toEqual<MatchConfig>({
-        changedFiles: {
-          all: ['testing-all'],
-          any: ['testing-any']
-        },
-        headBranch: ['testing-head'],
-        baseBranch: ['testing-base']
-      });
+      expect(result).toEqual(expected);
     });
 
     describe('and there are also unexpected options present', () => {
@@ -35,14 +36,7 @@ describe('toMatchConfig', () => {
 
       it('does not include the unexpected items in the returned MatchConfig object', () => {
         const result = toMatchConfig(config);
-        expect(result).toEqual<MatchConfig>({
-          changedFiles: {
-            all: ['testing-all'],
-            any: ['testing-any']
-          },
-          headBranch: ['testing-head'],
-          baseBranch: ['testing-base']
-        });
+        expect(result).toEqual(expected);
       });
     });
   });

__tests__/main.test.ts

@@ -16,7 +16,8 @@ const getPullMock = jest.spyOn(gh.rest.pulls, 'get');
 
 const yamlFixtures = {
   'branches.yml': fs.readFileSync('__tests__/fixtures/branches.yml'),
-  'only_pdfs.yml': fs.readFileSync('__tests__/fixtures/only_pdfs.yml')
+  'only_pdfs.yml': fs.readFileSync('__tests__/fixtures/only_pdfs.yml'),
+  'not_supported.yml': fs.readFileSync('__tests__/fixtures/not_supported.yml')
 };
 
 afterAll(() => jest.restoreAllMocks());
@@ -48,6 +49,14 @@ describe('run', () => {
     expect(addLabelsMock).toHaveBeenCalledTimes(0);
   });
 
+  it('does not add a label when no match config options match', async () => {
+    usingLabelerConfigYaml('not_supported.yml');
+    await run();
+
+    expect(addLabelsMock).toHaveBeenCalledTimes(0);
+    expect(removeLabelMock).toHaveBeenCalledTimes(0);
+  });
+
   it('(with sync-labels: true) it deletes preexisting PR labels that no longer match the glob pattern', async () => {
     const mockInput = {
       'repo-token': 'foo',

src/labeler.ts

@@ -151,6 +151,10 @@ export function checkMatchConfigs(
 }
 
 function checkMatch(changedFiles: string[], matchConfig: MatchConfig): boolean {
+  if (!Object.keys(matchConfig).length) {
+    return false;
+  }
+
   if (matchConfig.changedFiles?.all) {
     if (!checkAll(changedFiles, matchConfig.changedFiles.all)) {
       return false;