Build plugin executables with debug symbols

Sources/SPMTestSupport/Toolchain.swift

@@ -14,6 +14,7 @@ import Foundation
 import PackageModel
 import Workspace
 import TSCBasic
+import struct TSCUtility.SerializedDiagnostics
 
 #if os(macOS)
 private func macOSBundleRoot() throws -> AbsolutePath {
@@ -93,5 +94,28 @@ extension UserToolchain {
         return true
       #endif
     }
-
+
+    /// Helper function to determine whether serialized diagnostics work properly in the current environment.
+    public func supportsSerializedDiagnostics(otherSwiftFlags: [String] = []) -> Bool {
+        do {
+            try testWithTemporaryDirectory { tmpPath in
+                let inputPath = tmpPath.appending(component: "best.swift")
+                try localFileSystem.writeFileContents(inputPath, string: "func foo() -> Bool {\nvar unused: Int\nreturn true\n}\n")
+                let outputPath = tmpPath.appending(component: "foo")
+                let serializedDiagnosticsPath = tmpPath.appending(component: "out.dia")
+                let toolchainPath = self.swiftCompilerPath.parentDirectory.parentDirectory
+                try Process.checkNonZeroExit(arguments: ["/usr/bin/xcrun", "--toolchain", toolchainPath.pathString, "swiftc", inputPath.pathString, "-Xfrontend", "-serialize-diagnostics-path", "-Xfrontend", serializedDiagnosticsPath.pathString, "-g", "-o", outputPath.pathString] + otherSwiftFlags)
+                try Process.checkNonZeroExit(arguments: [outputPath.pathString])
+
+                let diaFileContents = try localFileSystem.readFileContents(serializedDiagnosticsPath)
+                let diagnosticsSet = try SerializedDiagnostics(bytes: diaFileContents)
+                if diagnosticsSet.diagnostics.isEmpty {
+                    throw StringError("does not support diagnostics")
+                }
+            }
+            return true
+        } catch {
+            return false
+        }
+    }
 }

Sources/Workspace/DefaultPluginScriptRunner.swift

@@ -17,6 +17,7 @@ import PackageModel
 import SPMBuildCore
 import TSCBasic
 
+import struct TSCUtility.SerializedDiagnostics
 import struct TSCUtility.Triple
 
 /// A plugin script runner that compiles the plugin source files as an executable binary for the host platform, and invokes it as a subprocess.
@@ -121,6 +122,8 @@ public struct DefaultPluginScriptRunner: PluginScriptRunner, Cancellable {
 
         // We use the toolchain's Swift compiler for compiling the plugin.
         var commandLine = [self.toolchain.swiftCompilerPathForManifests.pathString]
+
+        observabilityScope.emit(debug: "Using compiler \(self.toolchain.swiftCompilerPathForManifests.pathString)")
 
         // Get access to the path containing the PackagePlugin module and library.
         let pluginLibraryPath = self.toolchain.swiftPMLibrariesLocation.pluginLibraryPath
@@ -166,6 +169,8 @@ public struct DefaultPluginScriptRunner: PluginScriptRunner, Cancellable {
         // Add any extra flags required as indicated by the ManifestLoader.
         commandLine += self.toolchain.swiftCompilerFlags
 
+        commandLine.append("-g")
+
         // Add the Swift language version implied by the package tools version.
         commandLine += ["-swift-version", toolsVersion.swiftLanguageVersion.rawValue]
 

Tests/SPMBuildCoreTests/PluginInvocationTests.swift

@@ -412,12 +412,14 @@ class PluginInvocationTests: XCTestCase {
                 XCTAssertEqual(delegate.compiledResult, result)
                 XCTAssertNil(delegate.cachedResult)
 
-                // Check the serialized diagnostics. We should no longer have an error but now have a warning.
-                let diaFileContents = try localFileSystem.readFileContents(result.diagnosticsFile)
-                let diagnosticsSet = try SerializedDiagnostics(bytes: diaFileContents)
-                XCTAssertEqual(diagnosticsSet.diagnostics.count, 1)
-                let warningDiagnostic = try XCTUnwrap(diagnosticsSet.diagnostics.first)
-                XCTAssertTrue(warningDiagnostic.text.hasPrefix("variable \'unused\' was never used"), "\(warningDiagnostic)")
+                if try UserToolchain.default.supportsSerializedDiagnostics() {
+                    // Check the serialized diagnostics. We should no longer have an error but now have a warning.
+                    let diaFileContents = try localFileSystem.readFileContents(result.diagnosticsFile)
+                    let diagnosticsSet = try SerializedDiagnostics(bytes: diaFileContents)
+                    XCTAssertEqual(diagnosticsSet.diagnostics.count, 1, "unexpected diagnostics count in \(diagnosticsSet.diagnostics) from \(result.diagnosticsFile.pathString)")
+                    let warningDiagnostic = try XCTUnwrap(diagnosticsSet.diagnostics.first)
+                    XCTAssertTrue(warningDiagnostic.text.hasPrefix("variable \'unused\' was never used"), "\(warningDiagnostic)")
+                }
 
                 // Check that the executable file exists.
                 XCTAssertTrue(localFileSystem.exists(result.executableFile), "\(result.executableFile.pathString)")
@@ -455,12 +457,14 @@ class PluginInvocationTests: XCTestCase {
                 XCTAssertNil(delegate.compiledResult)
                 XCTAssertEqual(delegate.cachedResult, result)
 
-                // Check that the diagnostics still have the same warning as before.
-                let diaFileContents = try localFileSystem.readFileContents(result.diagnosticsFile)
-                let diagnosticsSet = try SerializedDiagnostics(bytes: diaFileContents)
-                XCTAssertEqual(diagnosticsSet.diagnostics.count, 1)
-                let warningDiagnostic = try XCTUnwrap(diagnosticsSet.diagnostics.first)
-                XCTAssertTrue(warningDiagnostic.text.hasPrefix("variable \'unused\' was never used"), "\(warningDiagnostic)")
+                if try UserToolchain.default.supportsSerializedDiagnostics() {
+                    // Check that the diagnostics still have the same warning as before.
+                    let diaFileContents = try localFileSystem.readFileContents(result.diagnosticsFile)
+                    let diagnosticsSet = try SerializedDiagnostics(bytes: diaFileContents)
+                    XCTAssertEqual(diagnosticsSet.diagnostics.count, 1)
+                    let warningDiagnostic = try XCTUnwrap(diagnosticsSet.diagnostics.first)
+                    XCTAssertTrue(warningDiagnostic.text.hasPrefix("variable \'unused\' was never used"), "\(warningDiagnostic)")
+                }
 
                 // Check that the executable file exists.
                 XCTAssertTrue(localFileSystem.exists(result.executableFile), "\(result.executableFile.pathString)")