test: add Missing unit tests for Grouping.Any

[SEWeiTung]

Seeing there're some missing unit cases for the extension of Enumerable.GroupBy().Any(), here's the fix for it.

[ghost]

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Issue Details

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For 'IIListProvider''s logic: If you want to check whether it has values or not, ">0" is enough. Otherwise, according to the original logic, if the source is IIListProvider and the 'GetCount()' <0, it will go to 'e.MoveNext();'. This is a bit too duplicated.

Author:	MaledongGit
Assignees:	-
Labels:	area-System.Linq, community-contribution
Milestone:	-

[eiriktsarpalis]

Hi @MaledongGit, and thank you for your contribution!

This will actually break the implementation.

The IListProvider.GetCount method will return -1 if it cannot cheaply calculate the count, in which case we need to fall back to the default enumerator-based approach. This change will result in any IListProvider with O(n) count calculation being erroneously reported as being empty.

I'm seeing a few tests fail in CI, but none actually originate from System.Linq.Tests. This suggests a potential gap in our test coverage. @MaledongGit would you be interested in changing this into a PR that adds a test like that?

[SEWeiTung]

@eiriktsarpalis:

Thanks for your tips, and what you said is just what I feel strange about.... XD

I'm seeing a few tests fail in CI, but none actually originate from System.Linq.Tests. This suggests a potential gap in our test coverage

Add into the 'tests' under System.LINQ folder ONLY? Is there anything class or if I should mock a class inherted from IIListProvider?

[SEWeiTung]

@eiriktsarpalis: I'd be happy if I could help :)

[eiriktsarpalis]

This is the file containing all Enumerable.Any tests: https://github.com/dotnet/runtime/blob/main/src/libraries/System.Linq/tests/AnyTests.cs. Adding a test would require finding an IListProvider<T> implementation that returns -1 if onlyIfCheap is set to true. One such example is the outer enumerator used by GroupBy:

runtime/src/libraries/System.Linq/src/System/Linq/Grouping.SpeedOpt.cs

Line 47 in 570efbb

onlyIfCheap ? -1 : Lookup<TKey, TElement>.Create(_source, _keySelector, _elementSelector, _comparer).Count;

[SEWeiTung]

Sorry to misunderstand it, and I've changed my PR to add the missing unit tests for Grouping().Any().

[eiriktsarpalis]

Thank you @MaledongGit!

[SEWeiTung]

Thank you @MaledongGit!

It's my fault, I should be responsible for it ;)