1721891 - "Error loading this URI: Unknown source" when trying to debug WebAssembly

Status: NEW

(DevTools :: Debugger, defect, P3)

Description

[teo.samarzija]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:90.0) Gecko/20100101 Firefox/90.0

Steps to reproduce:

Try opening this web-page and debug WebAssembly on it: https://flatassembler.github.io/analogClock.html

Actual results:

I get "Error loading this URI: Unknown source"

Expected results:

It should have shown WebAssembly Text Format, like Chrome does.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Javascript: WebAssembly' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Comment 2

[Lars T Hansen [:lth]]

Specific steps to reproduce:

• Open a new tab
• Open the devtools and select the debugger
• In the URL bar, enter https://flatassembler.github.io/analogClock.html and hit return
• (The page will load)
• In the debugger, expand the wasm:// line and then the flatassembler.github.io line
• Click on the line analogclock.html
• The debugger tab will show "Error loading this URI: Unknown source" instead of the wasm bytecode

However if the tab is now reloaded, the bytecode is shown as it should be.

Ultimately the error seems to originate in https://searchfox.org/mozilla-central/source/devtools/client/debugger/src/actions/sources/loadSourceText.js#30.

Comment 3

[teo.samarzija]

(In reply to Lars T Hansen [:lth] from comment #2)

Specific steps to reproduce:

• Open a new tab
• Open the devtools and select the debugger
• In the URL bar, enter https://flatassembler.github.io/analogClock.html and hit return
• (The page will load)
• In the debugger, expand the wasm:// line and then the flatassembler.github.io line
• Click on the line analogclock.html
• The debugger tab will show "Error loading this URI: Unknown source" instead of the wasm bytecode

However if the tab is now reloaded, the bytecode is shown as it should be.

Ultimately the error seems to originate in https://searchfox.org/mozilla-central/source/devtools/client/debugger/src/actions/sources/loadSourceText.js#30.

Why is this bug still marked "unconfirmed"? Have not you confirmed it is true?

Comment 4

[Lars T Hansen [:lth]]

(In reply to teo.samarzija from comment #3)

Why is this bug still marked "unconfirmed"? Have not you confirmed it is true?

So many buttons, so little time... Thanks for the notification.

Comment 5

[Jan Honza Odvarko [:Honza] (always need-info? me)]

Teo, can you please try this in Firefox 91 or Firefox Nightly. I can reproduce the problem in 90, but not in 91

Here is link to Fx Nightly build
https://www.mozilla.org/en-US/firefox/channel/desktop/

Honza

Comment 6

[teo.samarzija]

(In reply to Jan Honza Odvarko [:Honza] (always need-info? me) from comment #5)

Teo, can you please try this in Firefox 91 or Firefox Nightly. I can reproduce the problem in 90, but not in 91

Here is link to Fx Nightly build
https://www.mozilla.org/en-US/firefox/channel/desktop/

Honza

Just updated to Firefox 91. Apparently, the bug is still there.

Comment 7

[Hubert Boma Manilla (:bomsy)]

I tested this, i seem to be able to reproduce this.

Comment 8

[teo.samarzija]

Why do you think this is S3, AKA, not critical functionality? Firefox is supposed to lead the browsers in terms of WebAssembly support, after all, WebAssembly is the Mozilla's standard. Not being able to debug WebAssembly at all seems like a rather serious issue to me.

Comment 9

[Julian Descottes [:jdescottes]]

We opted for S3 for 2 reasons:

• there is a known workaround which is to reload the browser
• WebAssembly debugging impacts a fraction of devtools users

S3 doesn't mean it's not valid or important, and I understand it is important for your use case. But as a defect, it doesn't break DevTools, doesn't crash Firefox etc... We triage bugs in comparison with other defects, to know what to work on outside of our existing priorities. The team knows that there is a whole range of bugs around wasm debugging (they are all under https://bugzilla.mozilla.org/show_bug.cgi?id=1550784).