Create helper functions for temporary directories which supports new concurrency features

Sources/Basics/TemporaryFile.swift

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+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 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
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+import TSCBasic
+
+/// Creates a temporary directory and evaluates a closure with the directory path as an argument.
+/// The temporary directory will live on disk while the closure is evaluated and will be deleted when
+/// the cleanup closure is called. This allows the temporary directory to have an arbitrary lifetime.
+///
+/// - Parameters:
+///     - fileSystem: `FileSystem` which is used to construct temporary directory.
+///     - dir: If specified the temporary directory will be created in this directory otherwise environment
+///            variables TMPDIR, TEMP and TMP will be checked for a value (in that order). If none of the env
+///            variables are set, dir will be set to `/tmp/`.
+///     - prefix: The prefix to the temporary file name.
+///     - body: A closure to execute that receives the absolute path of the directory as an argument.
+///           If `body` has a return value, that value is also used as the
+///           return value for the `withTemporaryDirectory` function.
+///           The cleanup block should be called when the temporary directory is no longer needed.
+///
+/// - Throws: An error when creating directory and rethrows all errors from `body`.
+@available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+public func withTemporaryDirectory<Result>(
+    fileSystem: FileSystem = localFileSystem,
+    dir: AbsolutePath? = nil,
+    prefix: String = "TemporaryDirectory",
+    _ body: @escaping (AbsolutePath, @escaping (AbsolutePath) -> Void) async throws -> Result
+) throws -> Task<Result, Error> {
+    let temporaryDirectory = try createTemporaryDirectory(fileSystem: fileSystem, dir: dir, prefix: prefix)
+
+    let task: Task<Result, Error> = Task {
+        try await withTaskCancellationHandler {
+            try await body(temporaryDirectory) { path in
+                try? fileSystem.removeFileTree(path)
+            }
+        } onCancel: {
+            try? fileSystem.removeFileTree(temporaryDirectory)
+        }
+
+    }
+
+    return task
+}
+
+/// Creates a temporary directory and evaluates a closure with the directory path as an argument.
+/// The temporary directory will live on disk while the closure is evaluated and will be deleted afterwards.
+///
+/// - Parameters:
+///     - fileSystem: `FileSystem` which is used to construct temporary directory.
+///     - dir: If specified the temporary directory will be created in this directory otherwise environment
+///            variables TMPDIR, TEMP and TMP will be checked for a value (in that order). If none of the env
+///            variables are set, dir will be set to `/tmp/`.
+///     - prefix: The prefix to the temporary file name.
+///     - removeTreeOnDeinit: If enabled try to delete the whole directory tree otherwise remove only if its empty.
+///     - body: A closure to execute that receives the absolute path of the directory as an argument.
+///             If `body` has a return value, that value is also used as the
+///             return value for the `withTemporaryDirectory` function.
+///
+/// - Throws: An error when creating directory and rethrows all errors from `body`.
+@available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+public func withTemporaryDirectory<Result>(
+    fileSystem: FileSystem = localFileSystem,
+    dir: AbsolutePath? = nil,
+    prefix: String = "TemporaryDirectory",
+    removeTreeOnDeinit: Bool = false,
+    _ body: @escaping (AbsolutePath) async throws -> Result
+) throws -> Task<Result, Error> {
+    try withTemporaryDirectory(fileSystem: fileSystem, dir: dir, prefix: prefix) { path, cleanup in
+        defer { if removeTreeOnDeinit { cleanup(path) } }
+        return try await body(path)
+    }
+}
+
+private func createTemporaryDirectory(fileSystem: FileSystem, dir: AbsolutePath?, prefix: String) throws -> AbsolutePath {
+    // This random generation is needed so that
+    // it is more or less equal to generation using `mkdtemp` function
+    let letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+
+    let randomSuffix = String((0..<6).map { _ in letters.randomElement()! })
+
+    let tempDirectory = dir ?? fileSystem.tempDirectory
+    guard fileSystem.isDirectory(tempDirectory) else {
+        throw TempFileError.couldNotFindTmpDir(tempDirectory.pathString)
+    }
+
+    // Construct path to the temporary directory.
+    let templatePath = AbsolutePath(prefix + ".\(randomSuffix)", relativeTo: tempDirectory)
+
+    try fileSystem.createDirectory(templatePath, recursive: true)
+    return templatePath
+}

Tests/BasicsTests/TemporaryFileTests.swift

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+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 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
+ See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+ */
+
+import XCTest
+
+import TSCBasic
+
+import Basics
+
+@available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+class TemporaryAsyncFileTests: XCTestCase {
+    func testBasicTemporaryDirectory() async throws {
+        // Test can create and remove temp directory.
+        let path1: AbsolutePath = try await withTemporaryDirectory(removeTreeOnDeinit: true) { tempDirPath in
+            // Do some async task
+            try await Task.sleep(nanoseconds: 1_000)
+
+            XCTAssertTrue(localFileSystem.isDirectory(tempDirPath))
+            return tempDirPath
+        }.value
+        XCTAssertFalse(localFileSystem.isDirectory(path1))
+
+        // Test temp directory is not removed when its not empty.
+        let path2: AbsolutePath = try await withTemporaryDirectory { tempDirPath in
+            XCTAssertTrue(localFileSystem.isDirectory(tempDirPath))
+            // Create a file inside the temp directory.
+            let filePath = tempDirPath.appending(component: "somefile")
+            // Do some async task
+            try await Task.sleep(nanoseconds: 1_000)
+
+            try localFileSystem.writeFileContents(filePath, bytes: ByteString())
+            return tempDirPath
+        }.value
+        XCTAssertTrue(localFileSystem.isDirectory(path2))
+        // Cleanup.
+        try localFileSystem.removeFileTree(path2)
+        XCTAssertFalse(localFileSystem.isDirectory(path2))
+
+        // Test temp directory is removed when its not empty and removeTreeOnDeinit is enabled.
+        let path3: AbsolutePath = try await withTemporaryDirectory(removeTreeOnDeinit: true) { tempDirPath in
+            XCTAssertTrue(localFileSystem.isDirectory(tempDirPath))
+            let filePath = tempDirPath.appending(component: "somefile")
+            // Do some async task
+            try await Task.sleep(nanoseconds: 1_000)
+
+            try localFileSystem.writeFileContents(filePath, bytes: ByteString())
+            return tempDirPath
+        }.value
+        XCTAssertFalse(localFileSystem.isDirectory(path3))
+    }
+
+    func testCanCreateUniqueTempDirectories() async throws {
+        let (pathOne, pathTwo): (AbsolutePath, AbsolutePath) = try await withTemporaryDirectory(removeTreeOnDeinit: true) { pathOne in
+            let pathTwo: AbsolutePath = try await withTemporaryDirectory(removeTreeOnDeinit: true) { pathTwo in
+                // Do some async task
+                try await Task.sleep(nanoseconds: 1_000)
+
+                XCTAssertTrue(localFileSystem.isDirectory(pathOne))
+                XCTAssertTrue(localFileSystem.isDirectory(pathTwo))
+                // Their paths should be different.
+                XCTAssertTrue(pathOne != pathTwo)
+                return pathTwo
+            }.value
+            return (pathOne, pathTwo)
+        }.value
+        XCTAssertFalse(localFileSystem.isDirectory(pathOne))
+        XCTAssertFalse(localFileSystem.isDirectory(pathTwo))
+    }
+
+    func testCancelOfTask() async throws {
+        let task: Task<AbsolutePath, Error> = try withTemporaryDirectory { path in
+
+            try await Task.sleep(nanoseconds: 1_000_000_000)
+            XCTAssertTrue(Task.isCancelled)
+            XCTAssertFalse(localFileSystem.isDirectory(path))
+            return path
+        }
+        task.cancel()
+        do {
+            // The correct path is to throw an error here
+            let _ = try await task.value
+            XCTFail("The correct path here is to throw an error")
+        } catch {}
+    }
+}