Include the path to the platform's PrivateFrameworks directory in DYLD_FRAMEWORK_PATH when launching test runners (#8199)

This modifies the logic which sets the value of the
`DYLD_FRAMEWORK_PATH` environment variable when launching test runners
on Darwin when Xcode is installed: currently it includes the path to the
platform's developer "Frameworks" directory, and this change adds the
sibling "PrivateFrameworks" directory as well.

### Motivation:

XCTest includes some private support frameworks, and these frameworks
must be aligned with the public framework for testing to work correctly.
This ensures that if the path to the (public) frameworks directory is
specified, the aligned private frameworks directory is also included.

### Modifications:

- Add `$PLATFORM/Developer/Library/PrivateFrameworks` to the
`DYLD_FRAMEWORK_PATH` env var.

Resolves rdar://141564191

Author: stmontgomery

Sources/Commands/Utilities/TestingSupport.swift

@@ -219,8 +219,12 @@ enum TestingSupport {
         // Since XCTestHelper targets macOS, we need the macOS platform paths here.
         if let sdkPlatformPaths = try? SwiftSDK.sdkPlatformPaths(for: .macOS) {
             // appending since we prefer the user setting (if set) to the one we inject
-            env.appendPath(key: "DYLD_FRAMEWORK_PATH", value: sdkPlatformPaths.frameworks.pathString)
-            env.appendPath(key: "DYLD_LIBRARY_PATH", value: sdkPlatformPaths.libraries.pathString)
+            for frameworkPath in sdkPlatformPaths.frameworks {
+                env.appendPath(key: "DYLD_FRAMEWORK_PATH", value: frameworkPath.pathString)
+            }
+            for libraryPath in sdkPlatformPaths.libraries {
+                env.appendPath(key: "DYLD_LIBRARY_PATH", value: libraryPath.pathString)
+            }
         }
 
         // We aren't using XCTest's harness logic to run Swift Testing tests.

Sources/PackageModel/SwiftSDKs/SwiftSDK.swift

@@ -582,10 +582,10 @@ public struct SwiftSDK: Equatable {
         #if os(macOS)
         do {
             let sdkPaths = try SwiftSDK.sdkPlatformPaths(for: darwinPlatform, environment: environment)
-            extraCCFlags += ["-F", sdkPaths.frameworks.pathString]
-            extraSwiftCFlags += ["-F", sdkPaths.frameworks.pathString]
-            extraSwiftCFlags += ["-I", sdkPaths.libraries.pathString]
-            extraSwiftCFlags += ["-L", sdkPaths.libraries.pathString]
+            extraCCFlags.append(contentsOf: sdkPaths.frameworks.flatMap { ["-F", $0.pathString] })
+            extraSwiftCFlags.append(contentsOf: sdkPaths.frameworks.flatMap { ["-F", $0.pathString] })
+            extraSwiftCFlags.append(contentsOf: sdkPaths.libraries.flatMap { ["-I", $0.pathString] })
+            extraSwiftCFlags.append(contentsOf: sdkPaths.libraries.flatMap { ["-L", $0.pathString] })
             xctestSupport = .supported
         } catch {
             xctestSupport = .unsupported(reason: String(describing: error))
@@ -617,11 +617,11 @@ public struct SwiftSDK: Equatable {
     ///
     /// - SeeAlso: ``sdkPlatformPaths(for:environment:)``
     public struct PlatformPaths {
-        /// Path to the directory containing auxiliary platform frameworks.
-        public var frameworks: AbsolutePath
+        /// Paths of directories containing auxiliary platform frameworks.
+        public var frameworks: [AbsolutePath]
 
-        /// Path to the directory containing auxiliary platform libraries.
-        public var libraries: AbsolutePath
+        /// Paths of directories containing auxiliary platform libraries.
+        public var libraries: [AbsolutePath]
     }
 
     /// Returns `macosx` sdk platform framework path.
@@ -630,7 +630,13 @@ public struct SwiftSDK: Equatable {
         environment: Environment = .current
     ) throws -> (fwk: AbsolutePath, lib: AbsolutePath) {
         let paths = try sdkPlatformPaths(for: .macOS, environment: environment)
-        return (fwk: paths.frameworks, lib: paths.libraries)
+        guard let frameworkPath = paths.frameworks.first else {
+            throw StringError("could not determine SDK platform framework path")
+        }
+        guard let libraryPath = paths.libraries.first else {
+            throw StringError("could not determine SDK platform library path")
+        }
+        return (fwk: frameworkPath, lib: libraryPath)
     }
 
     /// Returns ``SwiftSDK/PlatformPaths`` for the provided Darwin platform.
@@ -652,17 +658,20 @@ public struct SwiftSDK: Equatable {
             throw StringError("could not determine SDK platform path")
         }
 
-        // For XCTest framework.
-        let fwk = try AbsolutePath(validating: platformPath).appending(
+        // For testing frameworks.
+        let frameworksPath = try AbsolutePath(validating: platformPath).appending(
             components: "Developer", "Library", "Frameworks"
         )
+        let privateFrameworksPath = try AbsolutePath(validating: platformPath).appending(
+            components: "Developer", "Library", "PrivateFrameworks"
+        )
 
-        // For XCTest Swift library.
-        let lib = try AbsolutePath(validating: platformPath).appending(
+        // For testing libraries.
+        let librariesPath = try AbsolutePath(validating: platformPath).appending(
             components: "Developer", "usr", "lib"
         )
 
-        let sdkPlatformFrameworkPath = PlatformPaths(frameworks: fwk, libraries: lib)
+        let sdkPlatformFrameworkPath = PlatformPaths(frameworks: [frameworksPath, privateFrameworksPath], libraries: [librariesPath])
         _sdkPlatformFrameworkPath[darwinPlatform] = sdkPlatformFrameworkPath
         return sdkPlatformFrameworkPath
     }