Fall back to downloading latest version from volta.sh on rate-limit

The GitHub.com server returns a 403 or 429 status code in case of rate-
limiting.
This commit adds a check for those status codes and tries to fetch the
latest volta version from https://volta.sh/latest-version instead.

The implementation is somewhat analog to how setup-node is implemented:
- https://github.com/actions/setup-node/blob/9f3a02bbd17adc05b078145bb8f676c84be77e89/src/installer.ts#L109-L129

Fixes: #108

Author: ZauberNerd

src/installer.test.ts

@@ -101,6 +101,10 @@ describe('buildLayout', () => {
 });
 
 describe('getVoltaVersion', function () {
+  afterAll(() => {
+    nock.restore();
+  });
+
   it('without user provided volta version', async function () {
     try {
       const scope = nock('https://api.github.com')
@@ -111,7 +115,7 @@ describe('getVoltaVersion', function () {
 
       scope.done();
     } finally {
-      nock.restore();
+      nock.cleanAll();
     }
   });
 
@@ -126,4 +130,23 @@ describe('getVoltaVersion', function () {
       `"volta-cli/action: Volta version must be >= 1.0.0 (you specified 0.6.5)"`
     );
   });
+
+  it('falls back to downloading from volta.sh/latest-version', async function () {
+    try {
+      const githubScope = nock('https://api.github.com')
+        .get('/repos/volta-cli/volta/releases/latest')
+        .reply(429, 'rate limit exceeded');
+
+      const voltaSHScope = nock('https://volta.sh')
+        .get('/latest-version')
+        .reply(200, '999.999.999');
+
+      expect(await getVoltaVersion('', 'some-token')).toEqual('999.999.999');
+
+      voltaSHScope.done();
+      githubScope.done();
+    } finally {
+      nock.cleanAll();
+    }
+  });
 });

src/installer.ts

@@ -31,12 +31,45 @@ async function getLatestVolta(authToken: string): Promise<string> {
     };
   }
 
-  const response = await http.getJson<{ name: string }>(url, headers);
-  if (!response.result) {
+  try {
+    const response = await http.getJson<{ name: string }>(url, headers);
+    if (!response.result) {
+      throw new Error(`volta-cli/action: Could not download latest release from ${url}`);
+    }
+
+    return semver.clean(response.result.name) as string;
+  } catch (error: unknown) {
+    if (
+      error instanceof hc.HttpClientError &&
+      (error.statusCode === 403 || error.statusCode === 429)
+    ) {
+      core.info(
+        `Received HTTP status code ${error.statusCode}. This usually indicates the rate limit has been exceeded`
+      );
+
+      return await getLatestVoltaFromVoltaSH();
+    } else {
+      throw error;
+    }
+  }
+}
+
+async function getLatestVoltaFromVoltaSH(): Promise<string> {
+  const url = 'https://volta.sh/latest-version';
+
+  core.info(`Falling back to download from ${url}`);
+
+  const http = new hc.HttpClient('volta-cli/action', [], {
+    allowRetries: true,
+    maxRetries: 3,
+  });
+
+  const response = await http.get(url);
+  if (response.message.statusCode !== 200) {
     throw new Error(`volta-cli/action: Could not download latest release from ${url}`);
   }
 
-  return semver.clean(response.result.name) as string;
+  return semver.clean(await response.readBody()) as string;
 }
 
 function voltaVersionHasSetup(version: string): boolean {