1764688 - Misuse of arrow function + this in MessageHandlerFrameActor.jsm

Status: RESOLVED FIXED

(Remote Protocol :: WebDriver BiDi, defect, P3)

Description

[Tooru Fujisawa [:arai]]

https://searchfox.org/mozilla-central/rev/d34f9713ae128a3138c2b70d8041a535f1049d19/remote/shared/messagehandler/transports/js-window-actors/MessageHandlerFrameActor.jsm#44

const MessageHandlerFrameActor = {
  registered: false,

  register: () => {
    if (this.registered) {
      return;
    }

...
    this.registered = true;

arrow function inherits this from the enclosing scope, and the this there is not the this value for the function call (so, MessageHandlerFrameActor for MessageHandlerFrameActor.register()), but the global this value.

The code work as expected because there's only one MessageHandlerFrameActor, and the global registered variable is falsy (undefined) at the beginning, and no other code touches it.

the code should use method definition instead.

Comment 1

[Julian Descottes [:jdescottes]]

Good point, thanks for filing :arai (and for taking the bug :) )

Comment 2

[Tooru Fujisawa [:arai]]

Attachment: Bug 1764688 - Fix this variable in MessageHandlerFrameActor.register. r?jdescottes!

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/52c74d875e24
Fix this variable in MessageHandlerFrameActor.register. r=jdescottes,webdriver-reviewers

Comment 4

[Marian-Vasile Laza]

https://hg.mozilla.org/mozilla-central/rev/52c74d875e24