Add a hostRuntimeEnvironment test helper function

This may fix the few tests which are failing due to missing DLLs on Windows in certain environments.

Author: jakepetroules

Sources/SWBTestSupport/RunDestinationTestSupport.swift

@@ -296,6 +296,26 @@ extension RunDestinationInfo {
             return .elf
         }
     }
+
+    /// An `Environment` object with `PATH` or `LD_LIBRARY_PATH` set appropriately pointing into the toolchain to be able to run a built Swift binary in tests.
+    ///
+    /// - note: On macOS, the OS provided Swift runtime is used, so `DYLD_LIBRARY_PATH` is never set for Mach-O destinations.
+    package func hostRuntimeEnvironment(_ core: Core, initialEnvironment: Environment = Environment()) -> Environment {
+        var environment = initialEnvironment
+        guard let toolchain = core.toolchainRegistry.defaultToolchain else {
+            return environment
+        }
+        switch imageFormat(core) {
+        case .elf:
+            environment.prependPath(key: "LD_LIBRARY_PATH", value: toolchain.path.join("usr/lib/swift/\(platform)").str)
+        case .pe:
+            environment.prependPath(key: .path, value: core.developerPath.path.join("Runtimes").join(toolchain.version.description).join("usr/bin").str)
+        case .macho:
+            // Fall back to the OS provided Swift runtime
+            break
+        }
+        return environment
+    }
 }
 
 extension _RunDestinationInfo {

Tests/SWBBuildSystemTests/BuildOperationTests.swift

@@ -144,15 +144,7 @@ fileprivate struct BuildOperationTests: CoreBasedTests {
             try await tester.checkBuild(runDestination: destination, signableTargets: Set(provisioningInputs.keys), signableTargetInputs: provisioningInputs) { results in
                 results.checkNoErrors()
 
-                let toolchain = try #require(core.toolchainRegistry.defaultToolchain)
-                let environment: Environment
-                if destination.imageFormat(core) == .elf {
-                    environment = ["LD_LIBRARY_PATH": toolchain.path.join("usr/lib/swift/\(destination.platform)").str]
-                } else {
-                    environment = .init()
-                }
-
-                let executionResult = try await Process.getOutput(url: URL(fileURLWithPath: projectDir.join("build").join("Debug\(destination.builtProductsDirSuffix)").join(core.hostOperatingSystem.imageFormat.executableName(basename: "tool")).str), arguments: [], environment: environment)
+                let executionResult = try await Process.getOutput(url: URL(fileURLWithPath: projectDir.join("build").join("Debug\(destination.builtProductsDirSuffix)").join(core.hostOperatingSystem.imageFormat.executableName(basename: "tool")).str), arguments: [], environment: destination.hostRuntimeEnvironment(core))
                 #expect(executionResult.exitStatus == .exit(0))
                 if core.hostOperatingSystem == .windows {
                     #expect(String(decoding: executionResult.stdout, as: UTF8.self) == "Hello world\r\n")
@@ -377,15 +369,7 @@ fileprivate struct BuildOperationTests: CoreBasedTests {
                     }
                 }
 
-                let toolchain = try #require(try await getCore().toolchainRegistry.defaultToolchain)
-                let environment: Environment
-                if destination.platform == "linux" {
-                    environment = ["LD_LIBRARY_PATH": toolchain.path.join("usr/lib/swift/linux").str]
-                } else {
-                    environment = .init()
-                }
-
-                let executionResult = try await Process.getOutput(url: URL(fileURLWithPath: projectDir.join("build").join("Debug\(destination.builtProductsDirSuffix)").join(core.hostOperatingSystem.imageFormat.executableName(basename: "tool")).str), arguments: [], environment: environment)
+                let executionResult = try await Process.getOutput(url: URL(fileURLWithPath: projectDir.join("build").join("Debug\(destination.builtProductsDirSuffix)").join(core.hostOperatingSystem.imageFormat.executableName(basename: "tool")).str), arguments: [], environment: destination.hostRuntimeEnvironment(core))
                 #expect(executionResult.exitStatus == .exit(0))
                 if core.hostOperatingSystem == .windows {
                     #expect(String(decoding: executionResult.stdout, as: UTF8.self) == "Hello world\r\n")
@@ -480,13 +464,7 @@ fileprivate struct BuildOperationTests: CoreBasedTests {
             try await tester.checkBuild(runDestination: destination, persistent: true) { results in
                 results.checkNoErrors()
 
-                let toolchain = try #require(try await getCore().toolchainRegistry.defaultToolchain)
-                let environment: Environment
-                if destination.platform == "linux" {
-                    environment = ["LD_LIBRARY_PATH": toolchain.path.join("usr/lib/swift/linux").str]
-                } else {
-                    environment = .init()
-                }
+                let environment = destination.hostRuntimeEnvironment(core)
 
                 let executionResult = try await Process.getOutput(url: URL(fileURLWithPath: projectDir.join("build").join("Debug\(destination.builtProductsDirSuffix)").join(core.hostOperatingSystem.imageFormat.executableName(basename: "test.xctest")).str), arguments: ["--testing-library", "swift-testing"], environment: environment)
                 #expect(String(decoding: executionResult.stderr, as: UTF8.self).contains("Test run started"))

Tests/SWBBuildSystemTests/CustomTaskBuildOperationTests.swift

@@ -30,12 +30,7 @@ fileprivate struct CustomTaskBuildOperationTests: CoreBasedTests {
             let destination: RunDestinationInfo = .host
             let core = try await getCore()
             let toolchain = try #require(core.toolchainRegistry.defaultToolchain)
-            let environment: [String: String]
-            if  destination.imageFormat(core) == .elf {
-                environment = ["LD_LIBRARY_PATH": toolchain.path.join("usr/lib/swift/\(destination.platform)").str]
-            } else {
-                environment = ProcessInfo.processInfo.environment.filter { $0.key.uppercased() == "PATH" } // important to allow swift to be looked up in PATH on Windows/Linux
-            }
+            let environment = destination.hostRuntimeEnvironment(core)
 
             let testProject = TestProject(
                 "aProject",
@@ -69,7 +64,7 @@ fileprivate struct CustomTaskBuildOperationTests: CoreBasedTests {
                         customTasks: [
                             TestCustomTask(
                                 commandLine: ["$(BUILD_DIR)/$(CONFIGURATION)$(EFFECTIVE_PLATFORM_NAME)/tool\(destination == .windows ? ".exe" : "")"],
-                                environment: environment,
+                                environment: .init(environment),
                                 workingDirectory: tmpDir.str,
                                 executionDescription: "My Custom Task",
                                 inputs: ["$(BUILD_DIR)/$(CONFIGURATION)$(EFFECTIVE_PLATFORM_NAME)/tool\(destination == .windows ? ".exe" : "")"],