1883905 - Allow tracing the full, possibly async execution of a given mochitest script line

Status: RESOLVED FIXED

(DevTools :: General, enhancement)

Description

[Alexandre Poirot [:ochameau]]

Bug 1721427 introduced DEBUG_STEP=true or DEBUG_STEP=50 to trace all executions of a given mochitest script, and pause it for a given amount of time in ms when giving a number.
This feature helps easily spot where an async test is stuck within the test script.
Now it doesn't help understanding why the test is paused.

We could introduce another instruction in order to be able to trace all execution, including the possible async execution being initiated from a given test line.

Comment 1

[Alexandre Poirot [:ochameau]]

Attachment: Bug 1883905 - [devtools] Allow the tracer to track all current thread's globals.

This typically help go from shared global to DevTools module loader globals (DevtoolsLoader and BrowserLoaders).

Comment 2

[Alexandre Poirot [:ochameau]]

Attachment: Bug 1883905 - [devtools] Trace test from a given line.

The existing feature DEBUG_STEP will help understand that the test is stuck on line 49
DEBUG_STEP=true ./mach mochitest browser_target_command_detach.js
On [STEP] browser_target_command_detach.js @ 49:3 :: ↦ await secondTargetCommand.startListening();

And the new DEBUG_TRACE_LINE feature will help understand where the code is stuck, deeply nested into async code of DevTools.
DEBUG_TRACE_LINE=49 ./mach mochitest browser_target_command_detach.js
On [STEP] target-command.js @ 512:7 :: ↦ await this._onFirstTarget;

Comment 3

[Alexandre Poirot [:ochameau]]

Attachment: Bug 1883905 - Simulate a timeout to investigate

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/e432142f97da
[devtools] Allow the tracer to track all current thread's globals. r=devtools-reviewers,nchevobbe
https://hg.mozilla.org/integration/autoland/rev/3e88f5e01d26
[devtools] Trace test from a given line. r=devtools-reviewers,nchevobbe

Comment 5

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/e432142f97da
https://hg.mozilla.org/mozilla-central/rev/3e88f5e01d26