chore(infrastructure): Fix local dev server (npm start command) (#3089

)

The `npm run screenshot:serve` command was recently broken by a refactoring. It would immediately exit instead of waiting to be killed by the user. That is now fixed.

test/screenshot/lib/controller.js

@@ -208,28 +208,18 @@ class Controller {
    * @return {!Promise<number>}
    */
   async getTestExitCode(reportData) {
-    const isOnline = await this.cli_.isOnline();
+    // Don't fail Travis builds when screenshots change. The diffs are reported in GitHub instead.
+    if (process.env.TRAVIS === 'true') {
+      return ExitCode.OK;
+    }
 
     // TODO(acdvorak): Store this directly in the proto so we don't have to recalculate it all over the place
     const numChanges =
       reportData.screenshots.changed_screenshot_list.length +
       reportData.screenshots.added_screenshot_list.length +
       reportData.screenshots.removed_screenshot_list.length;
 
-    if (numChanges === 0) {
-      return ExitCode.OK;
-    }
-
-    if (isOnline) {
-      if (process.env.TRAVIS === 'true') {
-        return ExitCode.OK;
-      }
-      return ExitCode.CHANGES_FOUND;
-    }
-
-    // Allow the report HTTP server to keep running by waiting for a promise that never resolves.
-    console.log('\nPress Ctrl-C to kill the report server');
-    await new Promise(() => {});
+    return numChanges > 0 ? ExitCode.CHANGES_FOUND : ExitCode.OK;
   }
 
   /**

test/screenshot/run.js

@@ -60,15 +60,17 @@ async function run() {
       console.log('Offline mode!');
     }
 
-    cmd()
-      .then(
-        (exitCode = 0) => {
+    cmd().then(
+      (exitCode = 0) => {
+        if (exitCode !== 0) {
           process.exit(exitCode);
-        },
-        (err) => {
-          console.error(err);
-          process.exit(ExitCode.UNKNOWN_ERROR);
-        });
+        }
+      },
+      (err) => {
+        console.error(err);
+        process.exit(ExitCode.UNKNOWN_ERROR);
+      }
+    );
   } else {
     console.error(`Error: Unknown command: '${cli.command}'`);
     process.exit(ExitCode.UNSUPPORTED_CLI_COMMAND);