fix: `protocol.handle` not intercepting file protocol (#39048)

fix: protocol.handle not intercepting file protocol

lib/browser/api/protocol.ts

@@ -9,7 +9,7 @@ const { registerSchemesAsPrivileged, getStandardSchemes, Protocol } = process._l
 const ERR_FAILED = -2;
 const ERR_UNEXPECTED = -9;
 
-const isBuiltInScheme = (scheme: string) => scheme === 'http' || scheme === 'https';
+const isBuiltInScheme = (scheme: string) => ['http', 'https', 'file'].includes(scheme);
 
 function makeStreamFromPipe (pipe: any): ReadableStream {
   const buf = new Uint8Array(1024 * 1024 /* 1 MB */);

spec/api-protocol-spec.ts

@@ -1114,13 +1114,34 @@ describe('protocol module', () => {
       await expect(net.fetch('test-scheme://foo')).to.eventually.be.rejectedWith(/ERR_UNKNOWN_URL_SCHEME/);
     });
 
-    it('receives requests to an existing scheme', async () => {
+    it('receives requests to the existing https scheme', async () => {
       protocol.handle('https', (req) => new Response('hello ' + req.url));
       defer(() => { protocol.unhandle('https'); });
       const body = await net.fetch('https://foo').then(r => r.text());
       expect(body).to.equal('hello https://foo/');
     });
 
+    it('receives requests to the existing file scheme', (done) => {
+      const filePath = path.join(__dirname, 'fixtures', 'pages', 'a.html');
+
+      protocol.handle('file', (req) => {
+        let file;
+        if (process.platform === 'win32') {
+          file = `file:///${filePath.replace(/\\/g, '/')}`;
+        } else {
+          file = `file://${filePath}`;
+        }
+
+        if (req.url === file) done();
+        return new Response(req.url);
+      });
+
+      defer(() => { protocol.unhandle('file'); });
+
+      const w = new BrowserWindow();
+      w.loadFile(filePath);
+    });
+
     it('receives requests to an existing scheme when navigating', async () => {
       protocol.handle('https', (req) => new Response('hello ' + req.url));
       defer(() => { protocol.unhandle('https'); });