debugger: assert test before accessing this.binding

[princejwesley]

assert this.binding before accessing it

[princejwesley]

/cc @indutny

[MylesBorins]

LGTM

[indutny]

LGTM

[thefourtheye]

LGTM

[Trott]

Did you manage to trigger this issue (so that your code failed with cannot read property of undefined or something like that when it should have failed with the assertion error)? Or did you simply see the issue in the code without triggering it?

[princejwesley]

@Trott I saw the issue in the code without triggering it.
Code before:

After:

[Trott]

LGTM

A test might be a good idea, or it might be overkill. Thoughts?

The test would be simple based on your code above:

'use strict';
require('../common');
const assert = require('assert');

assert.throws(() => { require('_debug_agent').start(); },
  assert.AssertionError);

[princejwesley]

@Trott I just have rearranged the code (predicate assertion first).
I couldn't find tests for _debug_agent.js. shall I create test/debugger/test-debugger-agent.js ?

[Trott]

@princejwesley I would put it in test/parallel rather than test/debugger. test-debugger-agent.js is fine for a file name, I think.

[princejwesley]

@Trott I have used test/parallel/test-debug-agent.js.

[Trott]

LGTM

CI: https://ci.nodejs.org/job/node-test-pull-request/1599/

[Trott]

CI looks good! Thanks for doing this!

[jasnell]

LGTM

[jasnell]

Landed in 826844e