[Debugger, JS] Add configuring debuggable browser

libraries/tools/kotlin-test-js-runner/karma-debug.js

@@ -3,12 +3,18 @@
  * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
+'use strict';
+
 const karma = require('karma');
 
 const cfg = karma.config;
 
 const karmaConfig = cfg.parseConfig(process.argv[2]);
 
+karmaConfig.singleRun = false;
+
+configureBrowsers(karmaConfig);
+
 const Server = karma.Server;
 const server = new Server(karmaConfig, function (exitCode) {
     console.log('Karma has exited with ' + exitCode);
@@ -26,4 +32,64 @@ server.on('browsers_ready', function () {
     }, 1000)
 });
 
-server.start();
+server.start();
+
+function configureBrowsers(config) {
+    let newBrowsers = config.browsers;
+    if (!Array.isArray(newBrowsers)) {
+        newBrowsers = [];
+    }
+
+    let browser = newBrowsers.find(browserName => isDebuggableBrowser(browserName, config));
+
+    if (!browser) {
+        console.warn(
+            'Unable to find debuggable browser: Only Google Chrome with 9222 remote debugging port supported\n',
+            'Fallback on Chrome Headless'
+        );
+        browser = 'ChromeHeadless'
+    }
+
+    config.browsers = [browser];
+}
+
+const REMOTE_DEBUGGING_PORT = '--remote-debugging-port';
+
+function isDebuggableBrowser(browserName, config) {
+    if ([
+        'ChromeHeadless',
+        'ChromeCanaryHeadless',
+        'ChromiumHeadless'
+    ].includes(browserName)) {
+        return true
+    }
+
+    const customLaunchers = config.customLaunchers;
+    if (!customLaunchers) {
+        return false;
+    }
+
+    let customLauncher = customLaunchers[browserName];
+    if (!customLauncher) {
+        return false;
+    }
+
+    const flags = customLauncher.flags;
+    if (!Array.isArray(flags)) {
+        return false;
+    }
+
+    const prefix = REMOTE_DEBUGGING_PORT + '=';
+    const value = flags.find(flag => typeof flag === 'string' && flag.indexOf(prefix) === 0);
+    if (value == null) {
+        return false;
+    }
+
+    const port = parseInt(value.substring(prefix.length), 10);
+    if (isNaN(port) || port !== 9222) {
+        console.warn(`Debugger expect 9222 port, but ${port} found`);
+        return false;
+    }
+
+    return true;
+}