Introduce AttributedString

[iCharlesHu]

This patch introduces struct AttributedString and tests. Markdown support is not included in this patch as it will be introduced in a separate package.

See Apple's documentation for more information.

[iCharlesHu]

@swift-ci please test

[millenomi]

cc @shahmishal @drexin @tomerd This is a large commit that is Delicate in a bunch of ways. I'm going to merge tomorrow after doing a deeper review, but keep an eye out for CI breakage in case we miss something.

[millenomi]

See suggestion + issue with AnyHashable bridging above. We should perhaps check if the AnyHashable is a NSObject-conforming value, and wrap it in a __SwiftValue if it isn't.

[iCharlesHu]

Addressed @millenomi 's comments.

[iCharlesHu]

@swift-ci please test

[millenomi]

@swift-ci please test and merge

[lxbndr]

Looks like _loadScopeAttributes(forSymbol:, from:) -> [String : Any.Type]? in Conversion.swift should be wrapped with #if os(macOS) as well. Windows build is failing:

D:\s\swift-corelibs-foundation\Sources\Foundation\AttributedString\Conversion.swift:295:24: error: cannot find 'dlopen' in scope
    guard let handle = dlopen(path, RTLD_NOLOAD) else {
                       ^~~~~~
D:\s\swift-corelibs-foundation\Sources\Foundation\AttributedString\Conversion.swift:295:37: error: cannot find 'RTLD_NOLOAD' in scope
    guard let handle = dlopen(path, RTLD_NOLOAD) else {
                                    ^~~~~~~~~~~
D:\s\swift-corelibs-foundation\Sources\Foundation\AttributedString\Conversion.swift:298:31: error: cannot find 'dlsym' in scope
    guard let symbolPointer = dlsym(handle, symbol) else {
                              ^~~~~

cc @iCharlesHu

[iCharlesHu]

Looks like _loadScopeAttributes(forSymbol:, from:) -> [String : Any.Type]? in Conversion.swift should be wrapped with #if os(macOS) as well. Windows build is failing:

D:\s\swift-corelibs-foundation\Sources\Foundation\AttributedString\Conversion.swift:295:24: error: cannot find 'dlopen' in scope
    guard let handle = dlopen(path, RTLD_NOLOAD) else {
                       ^~~~~~
D:\s\swift-corelibs-foundation\Sources\Foundation\AttributedString\Conversion.swift:295:37: error: cannot find 'RTLD_NOLOAD' in scope
    guard let handle = dlopen(path, RTLD_NOLOAD) else {
                                    ^~~~~~~~~~~
D:\s\swift-corelibs-foundation\Sources\Foundation\AttributedString\Conversion.swift:298:31: error: cannot find 'dlsym' in scope
    guard let symbolPointer = dlsym(handle, symbol) else {
                              ^~~~~

cc @iCharlesHu

Thanks @lxbndr ! I have a PR open here: #3060

[xwu]

Hey @iCharlesHu @millenomi, I must be kind of confused, but is it really the case that this project can no longer be run and tested on macOS at all?

Use of @_spi(Reflection) in this file means that one has to use a dev toolchain to compile the project, because the default toolchain distributed with Xcode doesn't include any SPI symbols. However, due to SR-12177, one must simultaneously also not use a dev toolchain but rather the default toolchain distributed with Xcode?

[millenomi]

Merging this will require that you use a matching toolchain; the main (trunk) snapshot toolchain from https://swift.org/download should in fact work.

In general, even on macOS, you should always be working on this code with a matching toolchain, rather than use Xcode's default. On Linux, this is enforced as build-script will build both the toolchain and Foundation for you in one go.

[millenomi]

… and I'll be looking at the SR this coming week because whoops.

I have been able to run recently on macOS despite that SR; I'll investigate.