Ensure attachments path directory is created

Sources/Testing/ABI/EntryPoints/EntryPoint.swift

@@ -8,6 +8,7 @@
 // See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 //
 
+private import Foundation
 private import _TestingInternals
 
 #if canImport(Synchronization)
@@ -622,9 +623,7 @@ public func configurationForEntryPoint(from args: __CommandLineArguments_v0) thr
 
   // Attachment output.
   if let attachmentsPath = args.attachmentsPath {
-    guard fileExists(atPath: attachmentsPath) else {
-      throw _EntryPointError.invalidArgument("---attachments-path", value: attachmentsPath)
-    }
+   try FileManager().createDirectory(atPath: attachmentsPath, withIntermediateDirectories: true)
     configuration.attachmentsPath = attachmentsPath
   }
 

Sources/Testing/Testing.docc/Attachments.md

@@ -244,8 +244,8 @@ after your tests finish running:
   `.build/attachments` by default. Visual Studio Code reports the paths to
   individual attachments in its Tests Results panel.
 - When using Swift Package Manager's `swift test` command, you can pass the
-  `--attachments-path` option. The testing library saves attachments to the
-  specified directory.
+  `--attachments-path` option. The testing library creates a directory at the
+  specified path and saves attachments to it.
 
   If you do not pass the `--attachments-path` option, the testing library does
   not save any attachments you record.

Tests/TestingTests/SwiftPMTests.swift

@@ -250,6 +250,78 @@ struct SwiftPMTests {
     #expect(fileContents.contains(UInt8(ascii: ">")))
   }
 
+  @Test(
+    "--attachments-path argument (creates missing directory)",
+    arguments: ["--attachments-path", "--experimental-attachments-path"]
+  )
+  func attachmentsPathCreatesMissingDirectory(argumentName: String) throws {
+    let tempDirPath = try temporaryDirectory()
+    let attachmentsPath = appendPathComponent("swt_attachments_\(UInt64.random(in: 0 ..< .max))", to: tempDirPath)
+    defer {
+      _ = remove(attachmentsPath)
+    }
+    #expect(!fileExists(atPath: attachmentsPath))
+    let configuration = try configurationForEntryPoint(withArguments: ["PATH", argumentName, attachmentsPath])
+    #expect(fileExists(atPath: attachmentsPath))
+    let actualPath = try #require(configuration.attachmentsPath, "Attachments path is not expected to be nil")
+    #expect(canonicalizePath(actualPath) == canonicalizePath(attachmentsPath))
+  }
+
+  @Test("--attachments-path argument (creates missing intermediate directories)")
+  func attachmentsPathCreatesMissingIntermediateDirectories() throws {
+    let tempDirPath = try temporaryDirectory()
+    let root = appendPathComponent("swt_attachments_\(UInt64.random(in: 0 ..< .max))", to: tempDirPath)
+    let intermediate = appendPathComponent("foo", to: root)
+    let attachmentsPath = appendPathComponent("bar", to: intermediate)
+    defer {
+      _ = remove(attachmentsPath)
+      _ = remove(intermediate)
+      _ = remove(root)
+    }
+    #expect(!fileExists(atPath: root))
+    let configuration = try configurationForEntryPoint(withArguments: ["PATH", "--attachments-path", attachmentsPath])
+    #expect(fileExists(atPath: root))
+    #expect(fileExists(atPath: intermediate))
+    #expect(fileExists(atPath: attachmentsPath))
+    let actualPath = try #require(configuration.attachmentsPath, "Attachments path is not expected to be nil")
+    #expect(canonicalizePath(actualPath) == canonicalizePath(attachmentsPath))
+  }
+
+  @Test("--attachments-path argument (accepts existing directory)")
+  func attachmentsPathAcceptsExistingDirectory() throws {
+    let tempDirPath = try temporaryDirectory()
+    #expect(fileExists(atPath: tempDirPath))
+    let configuration = try configurationForEntryPoint(withArguments: ["PATH", "--attachments-path", tempDirPath])
+    let actualPath = try #require(configuration.attachmentsPath, "Attachments path is not expected to be nil")
+    #expect(
+      canonicalizePath(actualPath) == canonicalizePath(tempDirPath),
+      "Canonicalized actual path (\(actualPath)) is not equal to canonicalized expected path (\(tempDirPath))",
+    )
+  }
+
+  @Test("--attachments-path argument (bad path)")
+  func attachmentsPathWithBadPath() throws {
+    let attachmentPathParent: String
+    let attachmentPath: String
+    #if !os(Windows)
+    attachmentPathParent = "/usr/bin"
+    attachmentPath = "\(attachmentPathParent)/cannot-save-attachments-here"
+    #else
+    attachmentPathParent = #"C:\Windows\System32"#
+    attachmentPath = "\(attachmentPathParent)\\cannot-save-attachments-here"
+    #endif
+
+    #expect(throws: (any Error).self) {
+      _ = try configurationForEntryPoint(withArguments: ["PATH", "--attachments-path", attachmentPath])
+    }
+  }
+
+  @Test("--attachments-path argument (missing path)")
+  func attachmentsPathWithMissingPath() throws {
+    let args = try parseCommandLineArguments(from: ["PATH", "--attachments-path"])
+    #expect(args.attachmentsPath == nil)
+  }
+
   @Test("--configuration-path argument", arguments: [
     "--configuration-path", "--experimental-configuration-path",
   ])