How to use inspector - 10 common examples

async function testNoCrashWithExceptionInCallback() {
  // There is a deliberate exception in the callback
  const session = new inspector.Session();
  session.connect();
  const error = new Error('We expect this');
  console.log('Expecting warning to be emitted');
  const promise = new Promise(waitForWarningSkipAsyncStackTraces);
  session.post('Console.enable', () => { throw error; });
  assert.strictEqual(await promise, error);
  session.disconnect();
}

const inspector = require('inspector');

const setDepth = 'Debugger.setAsyncCallStackDepth';

function verifyAsyncHookDisabled(message) {
  assert.strictEqual(async_wrap.async_hook_fields[kTotals], 0);
}

function verifyAsyncHookEnabled(message) {
  assert.strictEqual(async_wrap.async_hook_fields[kTotals], 4);
}

// By default inspector async hooks should not have been installed.
verifyAsyncHookDisabled('inspector async hook should be disabled at startup');

const session = new inspector.Session();
verifyAsyncHookDisabled('creating a session should not enable async hooks');

session.connect();
verifyAsyncHookDisabled('connecting a session should not enable async hooks');

session.post('Debugger.enable', () => {
  verifyAsyncHookDisabled('enabling debugger should not enable async hooks');

  session.post(setDepth, { invalid: 'message' }, () => {
    verifyAsyncHookDisabled('invalid message should not enable async hooks');

    session.post(setDepth, { maxDepth: 'five' }, () => {
      verifyAsyncHookDisabled('invalid maxDepth (string) should not enable ' +
                              'async hooks');

      session.post(setDepth, { maxDepth: NaN }, () => {

'IOPIPE_ENABLE_HEAPSNAPSHOT',
      this.config.heapSnapshot
    );
    this.enabled = this.profilerEnabled || this.heapEnabled;
    this.uploads = [];

    // pre-invoke hooks cannot be async, so create our own promise to wait on
    // before the post-invoke method runs
    this.pluginReadyPromise = Promise.resolve();

    this.hooks = {
      'pre:invoke': this.preInvoke.bind(this),
      'post:invoke': this.postInvoke.bind(this),
      'post:report': this.postReport.bind(this)
    };
    this.session = new inspector.Session();
    // promisify session.post
    this.sessionPost = (key, obj = {}) => {
      this.log(`${key}, opts = ${JSON.stringify(obj)}`);
      return new Promise((resolve, reject) => {
        this.session.post(
          key,
          obj,
          (err, msg) => (err ? reject(err) : resolve(msg))
        );
      });
    };

    this.coreUtil = null;

    return this;
  }

const notify = require("./notify");

const { Byte } = require("./metrics/byte");
const { Logical } = require("./metrics/logical");
const { Arithmetic } = require("./metrics/arithmetic");

/**
 * @see https://nodejs.org/api/modules.html#modules_the_module_wrapper
 */
// @ts-ignore: This uses an internal API.
const [header] = require("module").wrapper;

const { min, max } = Math;

const session = new Session();

const metrics = [
  {
    ...Arithmetic,
    weight: 1 / 3
  },
  {
    ...Byte,
    weight: 1 / 3
  },
  {
    ...Logical,
    weight: 1 / 3
  }
];

async function testNoCrashConsoleLogBeforeThrow() {
  const session = new inspector.Session();
  session.connect();
  let attempt = 1;
  process.on('warning', common.mustCall(3));
  session.on('inspectorNotification', () => {
    if (attempt++ > 3)
      return;
    console.log('console.log in handler');
    throw new Error('Exception in handler');
  });
  session.post('Runtime.enable');
  console.log('Did not crash');
  session.disconnect();
}

async function testConsoleLog() {
  const session = new inspector.Session();
  session.connect();
  session.on('inspectorNotification', (data) => {
    if (data.method === 'Runtime.consoleAPICalled') {
      assert.strictEqual(data.params.args.length, 1);
      assert.strictEqual(data.params.args[0].value, msg);
      asserted = true;
    }
  });
  session.post('Runtime.enable');
  console.log(msg);
  session.disconnect();
}

i: [0, 1, 2, 3, 4],
    accum: [0, 0, 1, 3, 6]
  };
  scopeCallback = function(error, result) {
    const i = cur++;
    let v, actual, expected;
    for (v of result.result) {
      actual = v.value.value;
      expected = expects[v.name][i];
      if (actual !== expected) {
        failures.push(`Iteration ${i} variable: ${v.name} ` +
          `expected: ${expected} actual: ${actual}`);
      }
    }
  };
  const session = new inspector.Session();
  session.connect();
  session.on('Debugger.paused',
             (notification) => debuggerPausedCallback(session, notification));
  let cbAsSecondArgCalled = false;
  assert.throws(() => {
    session.post('Debugger.enable', function() {}, function() {});
  }, TypeError);
  session.post('Debugger.enable', () => cbAsSecondArgCalled = true);
  session.post('Debugger.setBreakpointByUrl', {
    'lineNumber': 14,
    'url': pathToFileURL(path.resolve(__dirname, __filename)).toString(),
    'columnNumber': 0,
    'condition': ''
  });

  debuggedFunction();

'use strict';

const common = require('../common');

common.skipIfInspectorDisabled();

const { Session } = require('inspector');
const { inspect } = require('util');

const session = new Session();

common.expectsError(
  () => session.post('Runtime.evaluate', { expression: '2 + 2' }),
  {
    code: 'ERR_INSPECTOR_NOT_CONNECTED',
    type: Error,
    message: 'Session is not connected'
  }
);

session.connect();
session.post('Runtime.evaluate', { expression: '2 + 2' });

[1, {}, [], true, Infinity, undefined].forEach((i) => {
  common.expectsError(
    () => session.post(i),

const common = require('../common');
const { Worker } = require('worker_threads');

common.skipIfInspectorDisabled();

if (!process.env.HAS_STARTED_WORKER) {
  process.env.HAS_STARTED_WORKER = 1;
  new Worker(__filename);
  return;
}

const assert = require('assert');
const { Session } = require('inspector');

const session = new Session();
session.connect();
session.post('NodeTracing.start', {
  traceConfig: { includedCategories: ['node.perf'] }
}, common.mustCall((err) => {
  assert.deepStrictEqual(err, {
    code: -32000,
    message:
      'Tracing properties can only be changed through main thread sessions'
  });
}));
session.disconnect();

(async () => {
    let enabled = 0;
    registerAsyncHook(() => ++enabled, () => {});
    const session = new Session();
    session.connect();
    session.post = promisify(session.post);
    await session.post('Debugger.enable');
    strictEqual(enabled, 0);
    await session.post('Debugger.setAsyncCallStackDepth', { maxDepth: 42 });
    strictEqual(enabled, 1);
    throw new Error(eyecatcher);
  })();
} else {