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test(core): fix `Function#name` shim used in IE11 (#41439) 

Since IE11 does not support `Function#name`, we use a shim in tests that
parses the stringified function to extract the name. Previously, that
shim would cache the computed name on the function to speed up future
invocations. However, this resulted in incorrect values for functions
that "extended" other functions (such as the code generated by
TypeScript when downleveling ES2015 classes that extended other
classes).

To avoid issues such as #41416 (see also [internal discussion][1]), this
commit removes the caching of names. This is not expected to noticeably
affect performance, since (a) it is only used in tests, (b) it is only
used on browsers that do not natively support `Function#name` (i.e.
IE11) and (c) accessing function names is rare and inexpensive compared
to other operations that happen during testing.

[1]: https://angular-team.slack.com/archives/CB4UC1932/p1617285258058000

PR Close #41439
This commit is contained in:
George Kalpakas 2021-04-03 21:01:45 +03:00 committed by atscott
parent fcd190aa9c
commit ab47f417d6
1 changed files with 1 additions and 5 deletions
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6
third_party/shims_for_IE.js vendored
View File

@ -6,11 +6,7 @@ if (!Object.hasOwnProperty('name')) {
Object.defineProperty(Function.prototype, 'name', {
get: function() {
var matches = this.toString().match(/^\s*function\s*((?![0-9])[a-zA-Z0-9_$]*)\s*\(/);
var name = matches && matches.length > 1 ? matches[1] : "";
// For better performance only parse once, and then cache the
// result through a new accessor for repeated access.
Object.defineProperty(this, 'name', {value: name});
return name;
return matches && matches.length > 1 ? matches[1] : '';
}
});
}