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Implement FilePath.getCurrentWorkingDirectory() #71

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Implement FilePath.getCurrentWorkingDirectory() #71

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cc9e58a
Implement FilePath.getCurrentWorkingDirectory()
GeorgeLyon Nov 13, 2021
35dfffd
Make process-global nature of working directory more apparent
GeorgeLyon Nov 13, 2021
3aef396
Change name again
GeorgeLyon Nov 15, 2021
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12 changes: 12 additions & 0 deletions Sources/System/FilePath/FilePath.swift
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Original file line number Diff line number Diff line change
@@ -62,6 +62,18 @@ public struct FilePath {

// @available(macOS 10.16, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
extension FilePath {

/// Returns the current working directory of this process.
///
/// - Warning: This value is global to the proess and care should be taken to make sure it does not unexpectedly change.
public static func currentWorkingDirectory() throws -> FilePath {
guard let cwd = system_getcwd(nil, 0) else {
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This will allocate twice -- wouldn't it be better if we supplied this with an appropriately sized FilePath buffer and only resize it if we guessed wrong?

If desired, we can also eliminate allocations altogether by adding a variant that takes an inout FilePath. (I don't think we need that.)

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This might be better but given all the discussion about how this shouldn't be used often, I preferred the simpler variant rather than adding an infrequently taken second codepath.

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FilePath used to have a with-style internal init that used max-path-length, but it turns out there are multiple notions of such a thing and it's probably too complicated as-is (and wastes space). I agree that it doesn't matter for now; in the future we'd like to do it with something like an init on FilePath, which can make the space/speed tradeoffs.

throw Errno.current
}
defer { system_free(cwd) }
return FilePath(platformString: cwd)
}

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Way back when I was thinking this would be hosted on some kind of current process type, but I think this approach makes more sense. It's also available for typename elision IIUC:

func foo(_: FilePath)
let x = foo(.getCurrentWorkingDirectory())

I feel like making this a function rather than a throwing var makes sense (ignoring tools version concerns) as it will make a syscall.

/// The length of the file path, excluding the null terminator.
public var length: Int { _storage.length }
}
21 changes: 21 additions & 0 deletions Sources/System/Internals/Syscalls.swift
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Original file line number Diff line number Diff line change
@@ -123,3 +123,24 @@ internal func system_pipe(_ fds: UnsafeMutablePointer<Int32>) -> CInt {
return pipe(fds)
}
#endif

#if !os(Windows)
internal func system_getcwd(_ buf: UnsafeMutablePointer<CInterop.PlatformChar>?, _ size: size_t) -> UnsafeMutablePointer<CInterop.PlatformChar>? {
#if ENABLE_MOCKING
if mockingEnabled {
/// I'm not really sure how to mock this since `buf` is passed in uninitialized and it needs to return something
fatalError()
}
#endif
return getcwd(buf, size)
}
#endif

#if !os(Windows)
internal func system_free(_ ptr: UnsafeMutableRawPointer?) {
#if ENABLE_MOCKING
if mockingEnabled { _ = _mock(ptr) }
#endif
free(ptr)
}
#endif
6 changes: 6 additions & 0 deletions Tests/SystemTests/FilePathTests/FilePathTest.swift
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Original file line number Diff line number Diff line change
@@ -72,5 +72,11 @@ final class FilePathTest: XCTestCase {
}
}
}

func testCurrentWorkingDirectory() {
XCTAssertEqual(
try FilePath.currentWorkingDirectory().string,
FileManager.default.currentDirectoryPath)
}
}