Enable nullability in ArrayEditor

[gpetrou]

Proposed changes

• Enable nullability in ArrayEditor.

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.07980%. Comparing base (b0f86f1) to head (7ddb206).

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #12675         +/-   ##
===================================================
- Coverage   76.08157%   76.07980%   -0.00177%     
===================================================
  Files           3257        3257                 
  Lines         642145      642089         -56     
  Branches       47286       47286                 
===================================================
- Hits          488554      488500         -54     
- Misses        150041      150045          +4     
+ Partials        3550        3544          -6     

Flag	Coverage Δ
Debug	76.07980% <100.00000%> (-0.00177%)	⬇️
integration	18.09422% <20.00000%> (+0.00191%)	⬆️
production	50.01260% <100.00000%> (+0.00611%)	⬆️
test	96.96608% <100.00000%> (-0.00442%)	⬇️
unit	47.46481% <100.00000%> (+0.00719%)	⬆️

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[ricardobossan]

Please add a comment, explaining in detail why CollectionType?.GetElement()! will never return null.

[gpetrou]

This can actually be null, but changing it seems to require changing the base class which does not return null.
@lonitra should I change the base class? Alternatively, I could return string.Empty here instead, but this would mean a breaking change.

[Tanya-Solyanik]

The base class does not guarantee that CollectionType is not null, it should throw in the constructor when a null is passed in. Once we throw this exception, we can get rid of the question mark -
protected override Type CreateCollectionItemType() => CollectionType.GetElementType()!;

And for GetElementType returning null, I would throw InvalidOprationException, it could happen only if this type is not an array

[gpetrou]

@Tanya-Solyanik I added a separate commit with the proposed changes, but this affects lots of tests. Are we sure that we want to apply this change? If yes, I will update the tests. If not, any other suggestions?

[Tanya-Solyanik]

Yes, please update the tests.

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

Files not reviewed (1)

• src/System.Windows.Forms.Design/src/PublicAPI.Shipped.txt: Language not supported