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ObjectFactory<T> delegate should be covariant #101829

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alrz opened this issue May 3, 2024 · 5 comments · May be fixed by #102553
Open

ObjectFactory<T> delegate should be covariant #101829

alrz opened this issue May 3, 2024 · 5 comments · May be fixed by #102553
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api-ready-for-review API is ready for review, it is NOT ready for implementation area-Extensions-DependencyInjection
Milestone
9.0.0

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@alrz
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alrz commented May 3, 2024 •
edited by steveharter

Current workaround is to use the non-generic ObjectFactory and cast but that shouldn't be necessary.

ObjectFactory<A> a = ...;
ObjectFactory<B> b = ...;
ObjectFactory<Base> f = c ? a : b;
return f(...);

API Proposal

namespace Microsoft.Extensions.DependencyInjection;
- public delegate T ObjectFactory<T>(IServiceProvider serviceProvider, object?[]? arguments);
+ public delegate T ObjectFactory<out T>(IServiceProvider serviceProvider, object?[]? arguments);
@dotnet-policy-service dotnet-policy-service bot added the untriaged New issue has not been triaged by the area owner label May 3, 2024
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@stephentoub stephentoub added api-ready-for-review API is ready for review, it is NOT ready for implementation and removed untriaged New issue has not been triaged by the area owner labels May 3, 2024
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runtime/src/libraries/Microsoft.Extensions.DependencyInjection.Abstractions/src/ObjectFactoryT.cs

Line 15 in ee93104

public delegate T ObjectFactory<T>(IServiceProvider serviceProvider, object?[]? arguments);

@stephentoub stephentoub added this to the 9.0.0 milestone May 5, 2024
@alrz
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alrz commented May 5, 2024

Would it be possible to use params ReadOnlySpan<object> for the arguments here?
(I suppose this would be considered as a part of new params span set of APIs though.)

@stephentoub
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Would it be possible to use params ReadOnlySpan<object> for the arguments here? (I suppose this would be considered as a part of new params span set of APIs though.)

That would need to be an entirely different delegate and an entirely different set of APIs that take that delegate... just changing the delegate itself would be a binary breaking change. Feel free to open a separate issue with such a proposal.

@alrz
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alrz commented May 5, 2024

Opened #101889

alrz added a commit to alrz/runtime that referenced this issue May 22, 2024
@alrz
Make ObjectFactory<T> covariant
a233c69 
Closes dotnet#101829
@alrz alrz linked a pull request May 22, 2024 that will close this issue
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Make ObjectFactory<T> covariant alrz/runtime
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