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FileLock encounters a runtime error when the path of the locked file is long #277

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Merged
merged 1 commit into from
Jan 13, 2022
Merged

FileLock encounters a runtime error when the path of the locked file is long #277

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17 changes: 13 additions & 4 deletions Sources/TSCBasic/Lock.swift
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
/*
This source file is part of the Swift.org open source project

Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
Licensed under Apache License v2.0 with Runtime Library Exception

See http://swift.org/LICENSE.txt for license information
Expand Down Expand Up @@ -178,12 +178,21 @@ public final class FileLock {
throw FileSystemError(.notDirectory, lockFilesDirectory)
}
// use the parent path to generate unique filename in temp
var lockFileName = (resolveSymlinks(fileToLock.parentDirectory).appending(component: fileToLock.basename)).components.joined(separator: "_")
var lockFileName = (resolveSymlinks(fileToLock.parentDirectory).appending(component: fileToLock.basename)).components.joined(separator: "_") + ".lock"
if lockFileName.hasPrefix(AbsolutePath.root.pathString) {
lockFileName = String(lockFileName.dropFirst(AbsolutePath.root.pathString.count))
}
let lockFilePath = lockFilesDirectory.appending(component: lockFileName + ".lock")

// back off until it occupies at most `NAME_MAX` UTF-8 bytes but without splitting scalars
// (we might split clusters but it's not worth the effort to keep them together as long as we get a valid file name)
var lockFileUTF8 = lockFileName.utf8.suffix(Int(NAME_MAX))
while String(lockFileUTF8) == nil {
// in practice this will only be a few iterations
lockFileUTF8 = lockFileUTF8.dropFirst()
}
// we will never end up with nil since we have ASCII characters at the end
lockFileName = String(lockFileUTF8) ?? lockFileName
let lockFilePath = lockFilesDirectory.appending(component: lockFileName)

let lock = FileLock(at: lockFilePath)
return try lock.withLock(type: type, body)
}
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8 changes: 7 additions & 1 deletion Tests/TSCBasicTests/FileSystemTests.swift
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
/*
This source file is part of the Swift.org open source project

Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
Copyright (c) 2014 - 2022 Apple Inc. and the Swift project authors
Licensed under Apache License v2.0 with Runtime Library Exception

See http://swift.org/LICENSE.txt for license information
Expand Down Expand Up @@ -767,6 +767,12 @@ class FileSystemTests: XCTestCase {
let lockFile = tempDir.appending(component: "lockfile")

try _testFileSystemFileLock(fileSystem: localFileSystem, fileA: fileA, fileB: fileB, lockFile: lockFile)

// Test some long and edge case paths. We arrange to split between the C and the Cedilla if NAME_MAX is 255.
let longEdgeCase1 = tempDir.appending(component: String(repeating: "Façade! ", count: Int(NAME_MAX)).decomposedStringWithCanonicalMapping)
try localFileSystem.withLock(on: longEdgeCase1, type: .exclusive, {})
let longEdgeCase2 = tempDir.appending(component: String(repeating: "🏁", count: Int(NAME_MAX)).decomposedStringWithCanonicalMapping)
try localFileSystem.withLock(on: longEdgeCase2, type: .exclusive, {})
}
}

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