swift: force-unwrap file handles in swift-tools-support-core

[paveloom]

Description of changes

Fixes the following build errors:

/build/swift-tools-support-core-ac4871e/Sources/TSCBasic/FileSystem.swift:428:24: error: value of optional type 'UnsafeMutablePointer<FILE>?' (aka 'Optional<UnsafeMutablePointer<_IO_FILE>>') must be unwrapped to a value of type 'UnsafeMutablePointer<FILE>' (aka 'UnsafeMutablePointer<_IO_FILE>')
        defer { fclose(fp) }
                       ^
/build/swift-tools-support-core-ac4871e/Sources/TSCBasic/FileSystem.swift:458:24: error: value of optional type 'UnsafeMutablePointer<FILE>?' (aka 'Optional<UnsafeMutablePointer<_IO_FILE>>') must be unwrapped to a value of type 'UnsafeMutablePointer<FILE>' (aka 'UnsafeMutablePointer<_IO_FILE>')
        defer { fclose(fp) }
                       ^

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

Priorities

Add a 👍 reaction to pull requests you find important.

[hcsch]

The file handles are guaranteed to be non-nil at the point of unwrapping (otherwise the defer statements would not be reached) so force unwrapping them is sane.
I've tested the commits from this PR locally (rebased onto current nixos-unstable) on my Linux x86_64 machine and swift-tools-support-core and with it also swiftpm build for me and can be used to successfully build a swift package.

Thanks for making the PR :)

[hbjydev]

Can we get an urgent merge on this please? Swift has now been broken for over a month...

[donn]

+1 for urgency. Is there anything any of us can do to help this get merged faster?

[stephank]

Sorry for the delay. Maybe the Swift toolchain needs some more maintainers, in light of this.

The change looks good, though.

[hbjydev]

Sorry for the delay. Maybe the Swift toolchain needs some more maintainers, in light of this.

Probably not wrong @stephank -- I'd volunteer myself but I don't know enough about the toolchain to be anywhere near maintainer lmao

[wegank]

Result of nixpkgs-review pr 269015 run on x86_64-linux 1

2 packages failed to build:

• sourcekit-lsp (swiftPackages.sourcekit-lsp)
• swift-format (swiftPackages.swift-format)

5 packages built:

• swift (swiftPackages.swift)
• swift.man (swiftPackages.swift.man)
• swiftPackages.swift-docc
• swiftPackages.swift-driver
• swiftpm (swiftPackages.swiftpm)

[wegank]

Similar error for both failed packages:

error: builder for '/nix/store/91jlv5vxakkfsshlsdb091s7xli09q65-swift-format-5.8.drv' failed with exit code 1;
       last 10 log lines:
       >         defer { fclose(fp) }
       >                        ^
       > /build/swift-format-5.8-src/.build/checkouts/swift-tools-support-core/Sources/TSCBasic/FileSystem.swift:481:24: note: coalesce using '??' to provide a default when the optional value contains 'nil'
       >         defer { fclose(fp) }
       >                        ^
       >                           ?? <#default value#>
       > /build/swift-format-5.8-src/.build/checkouts/swift-tools-support-core/Sources/TSCBasic/FileSystem.swift:481:24: note: force-unwrap using '!' to abort execution if the optional value contains 'nil'
       >         defer { fclose(fp) }
       >                        ^
       >                          !
       For full logs, run 'nix log /nix/store/91jlv5vxakkfsshlsdb091s7xli09q65-swift-format-5.8.drv'.
error: builder for '/nix/store/w6c8ysbq039j51fkq9crzrd9rj5viwzs-sourcekit-lsp-5.8.drv' failed with exit code 1;
       last 10 log lines:
       >                           ?? <#default value#>
       > /build/sourcekit-lsp-5.8-src/.build/checkouts/swift-tools-support-core/Sources/TSCBasic/FileSystem.swift:458:24: note: force-unwrap using '!' to abort execution if the optional value contains 'nil'
       >         defer { fclose(fp) }
       >                        ^
       >                          !
       > [40/634] Compiling llvmSupport Path.cpp
       > [40/634] Compiling llvmSupport SourceMgr.cpp
       > [40/634] Compiling llvmSupport Signals.cpp
       > [40/634] Compiling llvmSupport Program.cpp
       > [40/634] Compiling llvmSupport Process.cpp
       For full logs, run 'nix log /nix/store/w6c8ysbq039j51fkq9crzrd9rj5viwzs-sourcekit-lsp-5.8.drv'.
error: 2 dependencies of derivation '/nix/store/b67sbs9c5zq3xp6fmd4lj49krs73ax1p-review-shell.drv' failed to build

[stephank]

I think this is fine for now. We should probably find a better structure for patches in shared swiftpm deps within the toolchain, but I'd rather have things working soon.

patchFlags may be able to replace the swiftpmMakeMutable hack, I'm not sure. It may not have been around when the swiftpm code was written. But I think that's something we should look at separately as well.