chore: handle CLI responses and formats (#1080)

Initial handling for CLI responses. Note that image responses are not
supported yet.

Author: OrKoN

src/bin/chrome-devtools.ts

@@ -11,8 +11,14 @@ import process from 'node:process';
 import yargs, {type Options, type PositionalOptions} from 'yargs';
 import {hideBin} from 'yargs/helpers';
 
-import {startDaemon, stopDaemon, sendCommand} from '../daemon/client.js';
+import {
+  startDaemon,
+  stopDaemon,
+  sendCommand,
+  handleResponse,
+} from '../daemon/client.js';
 import {isDaemonRunning} from '../daemon/utils.js';
+import type {CallToolResult} from '../third_party/index.js';
 import {VERSION} from '../version.js';
 
 import {commands} from './cliDefinitions.js';
@@ -25,6 +31,8 @@ if (argv.length === 0 || argv[0] === '--custom-help') {
   process.exit(0);
 }
 
+const defaultArgs = ['--viaCli', '--experimentalStructuredContent'];
+
 const y = yargs(argv)
   .scriptName('chrome-devtools')
   .showHelpOnFail(true)
@@ -44,7 +52,7 @@ y.command(
     // Extract args after 'start'
     const startIndex = process.argv.indexOf('start');
     const args = startIndex !== -1 ? process.argv.slice(startIndex + 1) : [];
-    await startDaemon([...args, '--via-cli']);
+    await startDaemon([...args, ...defaultArgs]);
   },
 );
 
@@ -75,6 +83,10 @@ for (const [commandName, commandDef] of Object.entries(commands)) {
     commandStr,
     commandDef.description,
     y => {
+      y.option('format', {
+        choices: ['text', 'json'],
+        default: 'text',
+      });
       for (const [argName, opt] of Object.entries(args)) {
         const type =
           opt.type === 'integer' || opt.type === 'number'
@@ -115,7 +127,7 @@ for (const [commandName, commandDef] of Object.entries(commands)) {
     async argv => {
       try {
         if (!isDaemonRunning()) {
-          await startDaemon(['--via-cli']);
+          await startDaemon(defaultArgs);
         }
 
         const commandArgs: Record<string, unknown> = {};
@@ -132,7 +144,12 @@ for (const [commandName, commandDef] of Object.entries(commands)) {
         });
 
         if (response.success) {
-          console.log(response.result);
+          console.log(
+            handleResponse(
+              JSON.parse(response.result) as unknown as CallToolResult,
+              argv['format'] as 'json' | 'text',
+            ),
+          );
         } else {
           console.error('Error:', response.error);
           process.exit(1);

src/daemon/client.ts

@@ -9,6 +9,7 @@ import fs from 'node:fs';
 import net from 'node:net';
 
 import {logger} from '../logger.js';
+import type {CallToolResult} from '../third_party/index.js';
 import {PipeTransport} from '../third_party/index.js';
 
 import type {DaemonMessage, DaemonResponse} from './types.js';
@@ -124,3 +125,27 @@ export async function stopDaemon() {
 
   await sendCommand({method: 'stop'});
 }
+
+export function handleResponse(
+  response: CallToolResult,
+  format: 'json' | 'text',
+): string {
+  if (response.isError) {
+    return JSON.stringify(response.content);
+  }
+  if (format === 'json') {
+    if (response.structuredContent) {
+      return JSON.stringify(response.structuredContent);
+    }
+    // Fall-through to text for backward compatibility.
+  }
+  const chunks = [];
+  for (const content of response.content) {
+    if (content.type === 'text') {
+      chunks.push(content.text);
+    } else {
+      throw new Error('Not supported response content type');
+    }
+  }
+  return format === 'text' ? chunks.join('') : JSON.stringify(chunks);
+}

src/daemon/types.ts

@@ -16,6 +16,7 @@ export type DaemonMessage =
 
 export interface DaemonResponse {
   success: boolean;
-  result: unknown;
+  // Stringified CallToolResult.
+  result: string;
   error: unknown;
 }

tests/daemon/client.test.ts

@@ -7,43 +7,111 @@
 import assert from 'node:assert';
 import {describe, it, afterEach} from 'node:test';
 
-import {startDaemon, stopDaemon} from '../../src/daemon/client.js';
+import {
+  handleResponse,
+  startDaemon,
+  stopDaemon,
+} from '../../src/daemon/client.js';
 import {isDaemonRunning} from '../../src/daemon/utils.js';
 
 describe('daemon client', () => {
-  afterEach(async () => {
-    if (isDaemonRunning()) {
+  describe('start/stop', () => {
+    afterEach(async () => {
+      if (isDaemonRunning()) {
+        await stopDaemon();
+        // Wait a bit for the daemon to fully terminate and clean up its files.
+        await new Promise(resolve => setTimeout(resolve, 1000));
+      }
+    });
+
+    it('should start and stop daemon', async () => {
+      assert.ok(!isDaemonRunning(), 'Daemon should not be running initially');
+
+      await startDaemon();
+      assert.ok(isDaemonRunning(), 'Daemon should be running after start');
+
       await stopDaemon();
-      // Wait a bit for the daemon to fully terminate and clean up its files.
       await new Promise(resolve => setTimeout(resolve, 1000));
-    }
-  });
+      assert.ok(!isDaemonRunning(), 'Daemon should not be running after stop');
+    });
 
-  it('should start and stop daemon', async () => {
-    assert.ok(!isDaemonRunning(), 'Daemon should not be running initially');
+    it('should handle starting daemon when already running', async () => {
+      await startDaemon();
+      assert.ok(isDaemonRunning(), 'Daemon should be running');
 
-    await startDaemon();
-    assert.ok(isDaemonRunning(), 'Daemon should be running after start');
+      // Starting again should be a no-op
+      await startDaemon();
+      assert.ok(isDaemonRunning(), 'Daemon should still be running');
+    });
 
-    await stopDaemon();
-    await new Promise(resolve => setTimeout(resolve, 1000));
-    assert.ok(!isDaemonRunning(), 'Daemon should not be running after stop');
+    it('should handle stopping daemon when not running', async () => {
+      assert.ok(!isDaemonRunning(), 'Daemon should not be running initially');
+
+      // Stopping when not running should be a no-op
+      await stopDaemon();
+      assert.ok(!isDaemonRunning(), 'Daemon should still not be running');
+    });
   });
 
-  it('should handle starting daemon when already running', async () => {
-    await startDaemon();
-    assert.ok(isDaemonRunning(), 'Daemon should be running');
+  describe('parsing', () => {
+    it('handles MCP response with text format', () => {
+      const textResponse = {content: [{type: 'text' as const, text: 'test'}]};
+      assert.strictEqual(handleResponse(textResponse, 'text'), 'test');
+    });
 
-    // Starting again should be a no-op
-    await startDaemon();
-    assert.ok(isDaemonRunning(), 'Daemon should still be running');
-  });
+    it('handles JSON response', () => {
+      const jsonResponse = {
+        content: [],
+        structuredContent: {
+          test: 'data',
+          number: 123,
+        },
+      };
+      assert.strictEqual(
+        handleResponse(jsonResponse, 'json'),
+        JSON.stringify(jsonResponse.structuredContent),
+      );
+    });
+
+    it('handles error response when isError is true', () => {
+      const errorResponse = {
+        isError: true,
+        content: [{type: 'text' as const, text: 'Something went wrong'}],
+      };
+      assert.strictEqual(
+        handleResponse(errorResponse, 'text'),
+        JSON.stringify(errorResponse.content),
+      );
+    });
 
-  it('should handle stopping daemon when not running', async () => {
-    assert.ok(!isDaemonRunning(), 'Daemon should not be running initially');
+    it('handles text response when json format is requested but no structured content', () => {
+      const textResponse = {
+        content: [{type: 'text' as const, text: 'Fall through text'}],
+      };
+      assert.deepStrictEqual(
+        handleResponse(textResponse, 'json'),
+        JSON.stringify(['Fall through text']),
+      );
+    });
 
-    // Stopping when not running should be a no-op
-    await stopDaemon();
-    assert.ok(!isDaemonRunning(), 'Daemon should still not be running');
+    it('throws error for unsupported content type', () => {
+      const unsupportedContentResponse = {
+        content: [
+          {
+            type: 'resource' as const,
+            resource: {
+              uri: 'data:image/png;base64,base64data',
+              blob: 'base64data',
+              mimeType: 'image/png',
+            },
+          },
+        ],
+        structuredContent: {},
+      };
+      assert.throws(
+        () => handleResponse(unsupportedContentResponse, 'text'),
+        new Error('Not supported response content type'),
+      );
+    });
   });
 });