Ensure browsers.json is in a good start before starting

Author: pimterry

src/browsers.ts

@@ -1,12 +1,35 @@
+import * as fs from 'fs';
 import * as path from 'path';
 import * as getBrowserLauncher from '@james-proxy/james-browser-launcher';
-import { Launch, LaunchOptions, BrowserInstance } from '@james-proxy/james-browser-launcher';
+import { LaunchOptions, BrowserInstance } from '@james-proxy/james-browser-launcher';
 import { promisify } from 'util';
 
+const readFile = promisify(fs.readFile);
+const deleteFile = promisify(fs.unlink);
+
+const browserConfigPath = (configPath: string) => path.join(configPath, 'browsers.json');
+
 export { BrowserInstance };
 
+export async function checkBrowserConfig(configPath: string) {
+    // It's not clear why, but sometimes the browser config can become corrupted, so it's not valid JSON
+    // If that happens JBL doesn't catch it, so we crash. To avoid that, we check it here on startup.
+
+    const browserConfig = browserConfigPath(configPath);
+    return readFile(browserConfig, 'utf8')
+    .then((contents) => JSON.parse(contents))
+    .catch((error) => {
+        if (error.code === 'ENOENT') return;
+
+        console.warn('Failed to read browser config on startup', error);
+        return deleteFile(browserConfig).catch((err) => {
+            console.error('Failed to clear broken config file:', err);
+        });
+    });
+}
+
 async function getLauncher(configPath: string) {
-    return await promisify(getBrowserLauncher)(path.join(configPath, 'browsers.json'));
+    return await promisify(getBrowserLauncher)(browserConfigPath(configPath));
 }
 
 export const getAvailableBrowsers = async (configPath: string) => {

src/index.ts

@@ -7,6 +7,7 @@ import { getStandalone, generateCACertificate } from 'mockttp';
 import updateCommand from '@oclif/plugin-update/lib/commands/update';
 
 import { HttpToolkitServer } from './httptoolkit-server';
+import { checkBrowserConfig } from './browsers';
 
 const canAccess = util.promisify(fs.access);
 const mkDir = util.promisify(fs.mkdir);
@@ -46,6 +47,7 @@ export async function runHTK(options: {
     const configPath = options.configPath || envPaths('httptoolkit', { suffix: '' }).config;
 
     await ensureDirectoryExists(configPath);
+    await checkBrowserConfig(configPath);
 
     const httpsConfig = await generateHTTPSConfig(configPath);