add a skip_auth_check input

action.yml

@@ -86,6 +86,18 @@ inputs:
     default: false
     required: false
 
+  skip_auth_check:
+    description: |-
+      Skip the check for an authenticated `gcloud` and suppress the warning
+      emitted when none is found. This is useful when the action is only used
+      to install components or to put `gcloud` on the PATH (for example, to
+      drive a local emulator) and no Google Cloud credentials are needed.
+
+      ⚠️ If you enable this, the action will not tell you when `gcloud` is
+      unauthenticated, even if a later step needs credentials.
+    default: false
+    required: false
+
 outputs:
   version:
     description: |-

src/main.ts

@@ -56,6 +56,7 @@ export async function run(): Promise<void> {
     let version = presence(core.getInput('version'));
     const components = core.getInput('install_components');
     const projectId = core.getInput('project_id');
+    const skipAuthCheck = parseBoolean(core.getInput('skip_auth_check'));
     const cache = parseBoolean(core.getInput('cache'));
 
     if (skipInstall) {
@@ -105,6 +106,8 @@ export async function run(): Promise<void> {
     if (credFile) {
       await authenticateGcloudSDK(credFile);
       core.info('Successfully authenticated');
+    } else if (skipAuthCheck) {
+      core.debug(`Skipping the authentication check ("skip_auth_check" was true)`);
     } else {
       let authed;
       try {

tests/setup-gcloud.test.ts

@@ -214,6 +214,41 @@ test('#run', { concurrency: true }, async (suite) => {
 
     assert.deepStrictEqual(mocks.setProject.mock.callCount(), 0);
   });
+
+  await suite.test('warns when there is no authentication', async (t) => {
+    const mocks = defaultMocks(t.mock, {});
+
+    // The suite restores process.env by assigning a copy back, which does not
+    // remove variables set by previous tests.
+    delete process.env.GOOGLE_GHA_CREDS_PATH;
+
+    await run();
+
+    assert.deepStrictEqual(mocks.isAuthenticated.mock.callCount(), 1);
+    assert.match(mocks.logWarning.mock.calls?.at(0)?.arguments?.at(0), /not authenticated/);
+  });
+
+  await suite.test('skips the authentication check when skip_auth_check is true', async (t) => {
+    const mocks = defaultMocks(t.mock, {
+      skip_auth_check: 'true',
+    });
+    await run();
+
+    assert.deepStrictEqual(mocks.isAuthenticated.mock.callCount(), 0);
+    assert.deepStrictEqual(mocks.logWarning.mock.callCount(), 0);
+  });
+
+  await suite.test('authenticates even when skip_auth_check is true', async (t) => {
+    const mocks = defaultMocks(t.mock, {
+      skip_auth_check: 'true',
+    });
+
+    process.env.GOOGLE_GHA_CREDS_PATH = '/foo/bar/path.json';
+
+    await run();
+
+    assert.deepStrictEqual(mocks.authenticateGcloudSDK.mock.callCount(), 1);
+  });
 });
 
 /**