#3180. Add @staticInterop tests. Part 1.

[sgrekhov]

No description provided.

[sgrekhov]

BTW @srujzs what types are allowed in an extension that provides members for @staticInterop class? I didn't fins any documentation about it.

import 'dart:js_interop';

@staticInterop
@JS()
class C {
}

extension Ext on C {
  external String getString();  // Ok
  external int getNumber();     // Ok
  external bool getBool();      // Ok
  external List<double> getList(); // Error: External JS interop member contains invalid types in its function signature: '*List<double>* Function()'.
  external Object getObject();  // Error: External JS interop member contains invalid types in its function signature: '*Object* Function()'.
  external JSObject getJSObject();  // Ok
}

[eernstg]

Added a handful of comments. A couple of questions came to mind, in particular about the support for having a @staticInterop extension type, and the ability to compile invocations of external extension instance members as raw JavaScript invocations without @JS on the extension.

[sgrekhov]

One description has been updated. Let’s wait for @srujzs’s response. I couldn’t find any documentation on how this annotation is intended to be used or what its limitations are, so the tests were written assuming that the current behavior is correct

[srujzs]

Tricky stuff! My general comments are:

• Annotating a mixin with @JS or @staticInterop or @anonymous should likely be an warning and we should make our transformer be more resilient to mixins.
• The ability to declare external extension members is entirely predicated on whether the on-type is a JS interop type. There are two: interop extension types and JS interop classes. If the on-type is not a valid JS interop type, we should expect an error on each of the external extension members.
• It should be a warning to put @staticInterop on extension types, member declarations, enums, etc. These can safely be a no-op.

This is one of the reasons why I wanted to move away from annotations with extension types with dart:js_interop (besides @JS as we still need renaming): every declaration must be validated that they can use that annotation.

what types are allowed in an extension that provides members for @staticInterop class? I didn't fins any documentation about it.

https://dart.dev/interop/js-interop/js-types#requirements-on-external-declarations-and-function-tojs

edit: Sorry for the back-and-forth around mixins. I believe we can modify our transformer and safely treat JS interop annotations on them as warnings, not errors.

[sgrekhov]

Thank you! Updated. Added new tests that expect errors/warnings for non JS interop classes annotated with @staticInterop. Removed tests checking that mixin and other types can be used in the interop. PTAL.

[eernstg]

LGTM.

@srujzs, it looks like you're happy about this PR at this time? I couldn't spot any comments from you that haven't been processed, as far as I can see.

I'll land it now, and if you have further comments then we can handle them in an additional PR.