ReflectionMirror - Swift Stdlib copypasta

Swift's powerful runtime reflection mechanism is gated under a System Programming Interface. To access it, you must add @_spi(Reflection) before a statement that imports the Swift Standard Library. This programming interface is removed from release toolchains, leaving developers with no choice but to use development toolchains for certain projects. Until now.

This package serves a purpose similar to philipturner/differentiation, in that it exposes a private API to the developer on release toolchains. Do not expect Apple to let any Xcode project depending on this package onto the iOS App Store. The purpose of bringing this feature to release toolchains isn't to build iOS apps, but to make it more accessible in situations where a development toolchain cannot be used. For example, iPad Swift Playgrounds.

How to use

This package copies reimplements the contents of ReflectionMirror.swift in the Swift Standard Library. It even gates the API-public functions under an SPI, although this one can be used on release toolchains. To use this library, replace all instances of the following:

@_spi(Reflection) import Swift

With an import of ReflectionMirror. This Swift module re-exports the Swift Standard Library, so you do not need a second import statement for import Swift.

@_spi(Reflection) import ReflectionMirror

You cannot SPI-import both Swift and ReflectionMirror at the same time on development toolchains, because that will cause a name collision with the following two functions. That is not an issue, because ReflectionMirror.swift contains the entire Reflection SPI of the Swift Standard Library (at least for now). This package also contains all of the SPI symbols because it reimplements that file. In other words, follow the instructions above and you'll be fine.

func _forEachField(
  of type: Any.Type,
  options: _EachFieldOptions = [],
  body: (UnsafePointer<CChar>, Int, Any.Type, _MetadataKind) -> Bool
) -> Bool

func _forEachFieldWithKeyPath<Root>(
  of type: Root.Type,
  options: _EachFieldOptions = [],
  body: (UnsafePointer<CChar>, PartialKeyPath<Root>) -> Bool
) -> Bool

Source code borrowed from apple/swift

• stdlib/public/core/Assert.swift (partially)
• stdlib/public/core/KeyPath.swift (partially)
• stdlib/public/core/ReflectionMirror.swift
• test/stdlib/ForEachField.swift

Source code borrowed from s4tf/s4tf

• Sources/TensorFlow/Core/KeyPathIterable.swift (for testing purposes inside the SwiftPM tests)
• Tests/TensorFlowTests/KeyPathIterableTests.swift