inspect: add promisified result for session.post

Author: ErickWendel

doc/api/inspector.md

@@ -183,15 +183,27 @@ changes:
 * `method` {string}
 * `params` {Object}
 * `callback` {Function}
+* Returns: {Promise|undefined}
 
 Posts a message to the inspector back-end. `callback` will be notified when
 a response is received. `callback` is a function that accepts two optional
 arguments: error and message-specific result.
 
+If the `callback` is not passed, then it'll return a Promise result.
+
 ```js
 session.post('Runtime.evaluate', { expression: '2 + 2' },
              (error, { result }) => console.log(result));
 // Output: { type: 'number', value: 4, description: '4' }
+
+// or for promise
+session.post('Runtime.evaluate', { expression: '2 + 2' })
+  .then((result) => {
+    console.log(result);
+  })
+  .catch((error) => console.error(error));
+
+// Output: { type: 'number', value: 4, description: '4' }
 ```
 
 The latest version of the V8 inspector protocol is published on the

lib/inspector.js

@@ -22,6 +22,7 @@ const { hasInspector } = internalBinding('config');
 if (!hasInspector)
   throw new ERR_INSPECTOR_NOT_AVAILABLE();
 
+const { promisify } = require('util');
 const EventEmitter = require('events');
 const { queueMicrotask } = require('internal/process/task_queues');
 const {
@@ -108,7 +109,7 @@ class Session extends EventEmitter {
    * @param {string} method
    * @param {Record<unknown, unknown>} [params]
    * @param {Function} [callback]
-   * @returns {void}
+   * @returns {void | Promise}
    */
   post(method, params, callback) {
     validateString(method, 'method');
@@ -128,13 +129,26 @@ class Session extends EventEmitter {
     }
     const id = this[nextIdSymbol]++;
     const message = { id, method };
+    const configureCbAndDispatch = (cb) => {
+      this[messageCallbacksSymbol].set(id, cb);
+      this[connectionSymbol].dispatch(JSONStringify(message));
+    };
+
     if (params) {
       message.params = params;
     }
     if (callback) {
-      this[messageCallbacksSymbol].set(id, callback);
+      configureCbAndDispatch(callback);
+      return;
     }
-    this[connectionSymbol].dispatch(JSONStringify(message));
+
+    const event = new EventEmitter();
+    const kOnFinish = Symbol('kOnFinish');
+    const promisifiedResult = promisify(event.once.bind(event))(kOnFinish);
+    const cb = (err, res) => event.emit(kOnFinish, err, res);
+    configureCbAndDispatch(cb);
+
+    return promisifiedResult;
   }
 
   /**

test/parallel/test-inspector-session-post-promisified.js

@@ -0,0 +1,61 @@
+'use strict';
+
+const common = require('../common');
+common.skipIfInspectorDisabled();
+
+const assert = require('assert');
+const {
+  Session
+} = require('inspector');
+const {
+  basename
+} = require('path');
+const currentFilename = basename(__filename);
+
+{
+  // Ensure that given a callback to session.post it won't return a promise result
+  const session = new Session();
+  session.connect();
+
+  const postResult = session.post('Profiler.enable', () => {
+    session.post('Profiler.start', () => {
+      session.post('Profiler.stop', (err, { profile }) => {
+
+        const { callFrame: { url } } = profile.nodes.find(({
+          callFrame
+        }) => callFrame.url.includes(currentFilename));
+        session.disconnect();
+        assert.deepStrictEqual(basename(url), currentFilename);
+      });
+    });
+  });
+
+  assert.strictEqual(postResult, undefined);
+}
+
+(async () => {
+  {
+    // Ensure that session.post returns a valid promisified result
+    const session = new Session();
+    session.connect();
+
+    await session.post('Profiler.enable');
+    await session.post('Profiler.start');
+
+    const {
+      profile
+    } = await session.post('Profiler.stop');
+
+    const {
+      callFrame: {
+        url
+      }
+    } = profile.nodes.find(({
+      callFrame
+    }) => {
+      return callFrame.url.includes(currentFilename);
+    });
+    session.disconnect();
+    assert.deepStrictEqual(basename(url), currentFilename);
+  }
+})().then(common.mustCall());