perf(injector): cache the results of the native class detection check

[thorn0]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Performance improvement

What is the current behavior? (You can also link to an open issue here)

Relatively expensive Function.prototype.toString is called every time a function is checked for being a native class. See #14268.

What is the new behavior (if this is a feature change)?

The results of the check are cached in the $$ngIsClass property of the function.

Does this PR introduce a breaking change?

no

Please check if the PR fulfills these requirements

• The commit message follows our guidelines: https://github.com/angular/angular.js/blob/master/CONTRIBUTING.md#commit-message-format

[lgalfaso]

I would call the property $$ngIsClass just to be sure there is no collision with another library that is also trying to identity if a given function is a class. Otherwise LGTM

[thorn0]

Done

[lgalfaso]

landed as 5ceb5db

[gkalpak]

@lgalfaso, should we backport this to v1.5.x ?

[lgalfaso]

@gkalpak I lean towards not backporting this, as we are adding a property that may or may not be expected. That said, I would not oppose to this being backported.

[gkalpak]

I don't feel strongly about it either. But if we consider the new property a potential BC, maybe we should mention it as such.

[thorn0]

Adding this property to a constructor by hand seems to be a way to turn off the deprecated behavior of the bindings even when native classes aren't used. That's something I'd like to do in my projects, so please backport this PR to 1.5. Or probably let's just add an option to $compileProvider for disabling that behavior .