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.NET Runtime Support for Swift Interop #93631

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24 of 41 tasks
Tracked by #95638
agocke opened this issue Oct 17, 2023 · 4 comments
Open
24 of 41 tasks
Tracked by #95638

.NET Runtime Support for Swift Interop #93631

agocke opened this issue Oct 17, 2023 · 4 comments
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area-System.Runtime.InteropServices User Story A single user-facing feature. Can be grouped under an epic.
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@agocke
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agocke commented Oct 17, 2023

Background

The Swift programming language is developed primarily by Apple for use in their product lines. It is a successor to the previous official language for these platforms, Objective-C. C# has had limited Objective-C interop support for quite a while and it powers frameworks like MAUI and Xamarin Forms that run on Apple devices.

Swift is now becoming the dominant language on Apple devices and eclipsing Objective-C. Many important libraries are now Swift-first or Swift-only. Objective-C binding is also becoming more difficult for these libraries. To continue to interoperate with external libraries and frameworks, C# needs to be able to interoperate directly with Swift, without going through an intermediate language.

Goals

In short, we should completely eliminate the required C/assembly sandwich that's currently required to call Swift from C# code, and potentially vice versa. In particular, neither C# nor Swift users should have to deal with lower-level system state, like registers or stack state, to call Swift from C#.

Non-goals

C# and Swift are different languages with different language semantics. It is not a goal to map every construct from one language to the other. However, there are some terms in both languages that are sufficiently similar that they can be mapped to an identical semantic term in the other language. Interop should be seen as a Venn diagram where each language forms its own circle, and interop is in the (much smaller) space of equivalent terms that are shared between them.

Work

The exact scope of work is bind the CryptoKit library with the projection tooling and runtime support. We'll need the calling convention work (described above) in the runtime. Above the OS level we'll need a code generation strategy to generate C# bindings for Swift. An existing project to do that exists as Binding Tools for Swift. This work also needs further definition, but is out of scope of the .NET runtime itself.

For the runtime we can focus on system-level interfacing. For that we will need:

@dotnet-issue-labeler dotnet-issue-labeler bot added the needs-area-label An area label is needed to ensure this gets routed to the appropriate area owners label Oct 17, 2023
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@agocke agocke added this to the 9.0.0 milestone Oct 17, 2023
@ghost ghost removed the untriaged New issue has not been triaged by the area owner label Oct 17, 2023
@vcsjones vcsjones removed the needs-area-label An area label is needed to ensure this gets routed to the appropriate area owners label Oct 17, 2023
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ghost commented Oct 17, 2023

Tagging subscribers to this area: @dotnet/interop-contrib
See info in area-owners.md if you want to be subscribed.

Issue Details

Background

The Swift programming language is developed primarily by Apple for use in their product lines. It is a successor to the previous official language for these platforms, Objective-C. C# has had limited Objective-C interop support for quite a while and it powers frameworks like MAUI and Xamarin Forms that run on Apple devices.

Swift is now becoming the dominant language on Apple devices and eclipsing Objective-C. Many important libraries are now Swift-first or Swift-only. Objective-C binding is also becoming more difficult for these libraries. To continue to interoperate with external libraries and frameworks, C# needs to be able to interoperate directly with Swift, without going through an intermediate language.

Goals

In short, we should completely eliminate the required C/assembly sandwich that's currently required to call Swift from C# code, and potentially vice versa. In particular, neither C# nor Swift users should have to deal with lower-level system state, like registers or stack state, to call Swift from C#.

Non-goals

C# and Swift are different languages with different language semantics. It is not a goal to map every construct from one language to the other. However, there are some terms in both languages that are sufficiently similar that they can be mapped to an identical semantic term in the other language. Interop should be seen as a Venn diagram where each language forms its own circle, and interop is in the (much smaller) space of equivalent terms that are shared between them.

Work

The exact scope of work is TBD. We can start to outline some basic requirements. We'll need the calling convention work (described above) in the runtime. Above the OS level we'll need a code generation strategy to generate C# bindings for Swift. An existing project to do that exists as Binding Tools for Swift. This work also needs further definition, but is out of scope of the .NET runtime itself.

For the runtime we can focus on system-level interfacing. For that we will need:

  • Calling convention design
    • Spec
    • Scenarios
      • Call basic functions
      • Tuples
      • Errors
      • Existential containers
      • Struct/class marshalling
  • Unit tests in .NET runtime
  • Integration tests or in-product usage (in runtime?)
    • CryptoKit?
Author: agocke
Assignees: -
Labels:

area-System.Runtime.InteropServices, area-Interop-coreclr

Milestone: 9.0.0

@agocke agocke added the User Story A single user-facing feature. Can be grouped under an epic. label Oct 23, 2023
@kotlarmilos
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@agocke Here is a list of libraries/frameworks people have asked for: https://github.com/xamarin/xamarin-macios/issues?q=is%3Aopen+is%3Aissue+label%3Arequires-swift. Most of them are Swift-only and could be used as definition of done (DoD) along with the CryptoKit.

@ShikiSuen
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ShikiSuen commented May 31, 2024

Is this PR aim to allow Swift (on Windows / Linux / macOS) to directly use dotNet 9 APIs without RemObject toolchains?

@filipnavara
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Is this PR aim to allow Swift (on Windows / Linux / macOS) to directly use dotNet 9 APIs without RemObject toolchains?

No, this is mapping in the opposite direction, allowing .NET 9+ to call Swift APIs.

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area-System.Runtime.InteropServices User Story A single user-facing feature. Can be grouped under an epic.
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