Bug 164844 – Web Inspector: Generator functions should have a displayable name when shown in stack traces

• Component: Web Inspector
• Status: RESOLVED FIXED

[Joseph Pecoraro]

Summary:
Generator functions should have a displayable name when shown in stack traces.

Test:
<script>
function* anotherGenerator(i) {
    console.trace();
}

function* generator(i){
    yield* anotherGenerator(i);
}

generator(10).next();
</script>

Steps to Reproduce:
1. Open test case
2. View Console for trace() output
  => Unexpected "anonymous function"s

Safari:

    [Log] Trace
    	(anonymous function) (generator.html:6)
    	generatorResume
    	(anonymous function) (generator.html:12)
    	generatorResume
    	Global Code (generator.html:23)

Chrome:

    console.trace
        anotherGenerator @ generator.html:6

Firefox:

    console.trace()
        anotherGenerator() generator.html:6
        generator() generator.html:12
        <anonymous> generator.html:23

At the very least we should name the anonymous functions to match the generators that generated them, while being careful not to put an identifier name in the lexical scope. So I would expect something like this (and perhaps in the future eliminating the built-in functions):

    [Log] Trace
	anotherGenerator (generator.html:6)
	generatorResume
	generator (generator.html:12)
	generatorResume
	Global Code (generator.html:23)

Note:
• The same is true of async functions, but they also have other issues right now (they show up twice in the stack trace, so we should clean that up differently)

[Radar WebKit Bug Importer]

<rdar://problem/29300697>

[Joseph Pecoraro]

Created attachment 295002 [details]
[PATCH] Proposed Fix

There may be a better way of doing this. And eventually we'll probably want to do the same for Async functions. Lets see what the JSC folks think.

[Joseph Pecoraro]

Comment on attachment 295002 [details]
[PATCH] Proposed Fix

View in context: https://bugs.webkit.org/attachment.cgi?id=295002&action=review

> LayoutTests/inspector/debugger/js-stacktrace-expected.txt:148
> +        "functionName": "generator2",

Without this change all of these "generator#" strings would be the empty string, and show as (anonymous function) in Web Inspector.

[Yusuke Suzuki]

Comment on attachment 295002 [details]
[PATCH] Proposed Fix

Can you add a test to ensure the following case?

function* generator(factory)
{
    console.log(generator === factory); // should be true.
}
generator(generator).next();

[Build Bot]

Comment on attachment 295002 [details]
[PATCH] Proposed Fix

Attachment 295002 [details] did not pass mac-debug-ews (mac):
Output: http://webkit-queues.webkit.org/results/2528657

New failing tests:
js/methods-names-should-not-be-in-lexical-scope.html
imported/w3c/web-platform-tests/custom-elements/attribute-changed-callback.html
fast/dom/MutationObserver/observe-exceptions.html
http/tests/websocket/tests/hybi/websocket-constructor-protocols.html
imported/w3c/web-platform-tests/custom-elements/CustomElementRegistry.html
js/class-syntax-method-names.html
fast/text/font-face-set-javascript.html

[Build Bot]

Created attachment 295014 [details]
Archive of layout-test-results from ews115 for mac-yosemite

The attached test failures were seen while running run-webkit-tests on the mac-debug-ews.
Bot: ews115  Port: mac-yosemite  Platform: Mac OS X 10.10.5

[Joseph Pecoraro]

(In reply to comment #5)
> Comment on attachment 295002 [details]
> [PATCH] Proposed Fix
> 
> Attachment 295002 [details] did not pass mac-debug-ews (mac):
> Output: http://webkit-queues.webkit.org/results/2528657
> 
> New failing tests:
> js/methods-names-should-not-be-in-lexical-scope.html

These are real ASSERTs, I can't set a null string as the inferred name. I'll upload a new patch to let the bots re-run.

[Joseph Pecoraro]

Created attachment 295093 [details]
[PATCH] For Landing

[Joseph Pecoraro]

<https://trac.webkit.org/changeset/208885>