Support using a Swift file as a build tool plugin executable #8807
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A Swift file can be executed directly in the shell. Typically the file begins with a `#/usr/bin/swift` or an equivalent `xcrun` incantation, and then simply running `swift MyFile.swift` will automatically compile and execute it. Build tool plugins often leverage Swift, but to do so they add two targets, a `.plugin` and an `.executableTarget`. The executable target builds a binary that the plugin tool then calls during a build. Often this is more heavyweight than needed. By passing the path to a Swift file to the `executable` argument of the `.buildCommand` returned from your build tool plugin, you could bypass the need to create a separate executable target and just execute the file directly. However, because SwiftPM executes build tool plugins within a sandbox the sandbox script needs to be ammended with the clang module cache temporary directory so that the swift compiler can write the modules it needs to execute the file. Ammend the sandbox script to add write permissions to the root tmp directory that LLVM uses to write clang modules. With this addition you can now use a .swift file as a build tool plugin executable. rdar://152874736
plemarquand
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jakepetroules,
dschaefer2,
shawnhyam,
bripeticca,
owenv,
bkhouri,
cmcgee1024 and
daveyc123
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owenv
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Jun 11, 2025
MahdiBM
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Jun 12, 2025
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| #!/usr/bin/swift | |||
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does this support pointing to any executable or is it locked to swift? just checking ... one might prefer to use e.g. bash sometimes.
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You could use a bash script as a build tool plugin executable and I believe it would work today, without this patch, yes.
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cmcgee1024
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Jun 13, 2025
Fixtures/Miscellaneous/Plugins/SwiftFilePlugin/SimpleSwiftScript.swift
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Fixtures/Miscellaneous/Plugins/SwiftFilePlugin/SimpleSwiftScript.swift
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A Swift file can be executed directly in the shell. Typically the file begins with a
#/usr/bin/swiftor an equivalentxcrunincantation, and then simply runningswift MyFile.swiftwill automatically compile and execute it.Build tool plugins often leverage Swift, but to do so they add two targets, a
.pluginand an.executableTarget. The executable target builds a binary that the plugin tool then calls during a build.Often this is more heavyweight than needed. By passing the path to a Swift file to the
executableargument of the.buildCommandreturned from your build tool plugin, you could bypass the need to create a separate executable target and just execute the file directly.However, because SwiftPM executes build tool plugins within a sandbox the sandbox script needs to be ammended with the clang module cache temporary directory so that the swift compiler can write the modules it needs to execute the file.
Ammend the sandbox script to add write permissions to the root tmp directory that LLVM uses to write clang modules. With this addition you can now use a .swift file as a build tool plugin executable.
rdar://152874736