feat: Allow use of --discovery-url parameter (#1377)

Make it possible for the user to call the generate script passing
a --discovery-url parameter

src/generator/generate.ts

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+import * as minimist from 'minimist';
 import * as path from 'path';
 import * as rimraf from 'rimraf';
 import {install} from 'source-map-support';
@@ -24,13 +25,16 @@ import {Generator} from './generator';
 // enable source map support
 install();
 
+const argv = minimist(process.argv.slice(2));
+const DEFAULT_DISCOVERY_URL = 'https://www.googleapis.com/discovery/v1/apis/';
+const discoveryUrl = argv['discovery-url'];
+
 const debug = true;
-const args = process.argv.slice(2);
 const gen = new Generator({debug, includePrivate: false});
 
 async function main() {
-  if (args.length) {
-    args.forEach(async url => {
+  if (!discoveryUrl && argv._.length > 0) {
+    argv._.forEach(async url => {
       await gen.generateAPI(url);
       console.log('Generated API for ' + url);
     });
@@ -39,7 +43,7 @@ async function main() {
     const apiPath = path.join(__dirname, '../../../src/apis');
     await util.promisify(rimraf)(apiPath);
     console.log('Generating APIs...');
-    await gen.generateAllAPIs();
+    await gen.generateAllAPIs(discoveryUrl || DEFAULT_DISCOVERY_URL);
     console.log('Finished generating APIs!');
   }
 }

src/generator/generator.ts

@@ -28,10 +28,6 @@ const cliArgs = argv._;
 const writeFile = util.promisify(fs.writeFile);
 const readDir = util.promisify(fs.readdir);
 
-const DISCOVERY_URL = argv['discovery-url'] ?
-    argv['discovery-url'] :
-    (cliArgs.length ? cliArgs[0] :
-                      'https://www.googleapis.com/discovery/v1/apis/');
 const FRAGMENT_URL =
     'https://storage.googleapis.com/apisnippets-staging/public/';
 
@@ -177,9 +173,9 @@ export class Generator {
   /**
    * Generate all APIs and write to files.
    */
-  async generateAllAPIs() {
+  async generateAllAPIs(discoveryUrl: string) {
     const headers = this.options.includePrivate ? {} : {'X-User-Ip': '0.0.0.0'};
-    const res = await this.request<Schemas>({url: DISCOVERY_URL, headers});
+    const res = await this.request<Schemas>({url: discoveryUrl, headers});
     const apis = res.data.items;
     const queue = new Q({concurrency: 10});
     console.log(`Generating ${apis.length} APIs...`);