[6.0][Macros] Ensure plugin process is alive before sending a message

lib/ASTGen/Sources/ASTGen/PluginHost.swift

@@ -138,15 +138,15 @@ struct CompilerPlugin {
   }
 
   func sendMessageAndWaitWithoutLock(_ message: HostToPluginMessage) throws -> PluginToHostMessage {
+    guard !Plugin_spawnIfNeeded(opaqueHandle) else {
+      throw PluginError.stalePlugin
+    }
     try sendMessage(message)
     return try waitForNextMessage()
   }
 
   func sendMessageAndWait(_ message: HostToPluginMessage) throws -> PluginToHostMessage {
     try self.withLock {
-      guard !Plugin_spawnIfNeeded(opaqueHandle) else {
-        throw PluginError.stalePlugin
-      }
       return try sendMessageAndWaitWithoutLock(message);
     }
   }

test/Macros/macro_plugin_server_mod.swift

@@ -0,0 +1,122 @@
+// REQUIRES: swift_swift_parser
+// REQUIRES: OS=macosx
+
+// RUN: %empty-directory(%t)
+// RUN: %empty-directory(%t/plugins)
+// RUN: split-file %s %t
+
+//== Build the plugin library
+// RUN: %host-build-swift \
+// RUN:   -swift-version 5 \
+// RUN:   -emit-library \
+// RUN:   -o %t/plugins/%target-library-name(MacroDefinition) \
+// RUN:   -module-name=MacroDefinition \
+// RUN:   %t/MacroDefinition.swift \
+// RUN:   -g -no-toolchain-stdlib-rpath
+
+// RUN: %host-build-swift \
+// RUN:   -swift-version 5 \
+// RUN:   -emit-library \
+// RUN:   -o %t/plugins/%target-library-name(EvilMacros) \
+// RUN:   -module-name=EvilMacros \
+// RUN:   %t/EvilMacros.swift \
+// RUN:   -g -no-toolchain-stdlib-rpath
+
+// RUN: %cmake-c-compiler \
+// RUN:   %c-flags -target %host_triple -isysroot %host_sdk \
+// RUN:   -shared -o %t/plugins/libCrashOnLoad.dylib \
+// RUN:   %t/CrashOnLoad.c
+
+// RUN: %target-swift-frontend \
+// RUN:   -swift-version 5 \
+// RUN:   -emit-module -o \
+// RUN:   %t/MacroLibrary.swiftmodule \
+// RUN:   %t/MacroLibrary.swift \
+// RUN:   -module-name MacroLibrary \
+// RUN:   -external-plugin-path %t/plugins#%swift-plugin-server
+
+// RUN: env SWIFT_DUMP_PLUGIN_MESSAGING=1 %target-swift-frontend \
+// RUN:   -typecheck -verify \
+// RUN:   -I %t \
+// RUN:   -swift-version 5 \
+// RUN:   -external-plugin-path %t/plugins#%swift-plugin-server \
+// RUN:   -module-name MyApp \
+// RUN:   %t/app.swift \
+// RUN:   2>&1 | tee %t/macro-expansions.txt
+
+// RUN: %FileCheck -strict-whitespace %s < %t/macro-expansions.txt
+
+// CHECK: ->(plugin:[[#PID1:]]) {"getCapability":{"capability":{"protocolVersion":[[#PROTOCOL_VERSION:]]}}}
+// CHECK-NEXT: <-(plugin:[[#PID1]]) {"getCapabilityResult":{"capability":{"features":["load-plugin-library"],"protocolVersion":[[#PROTOCOL_VERSION]]}}}
+// CHECK-NEXT: ->(plugin:[[#PID1]]) {"loadPluginLibrary":{"libraryPath":"{{.*}}CrashOnLoad.{{.*}}","moduleName":"CrashOnLoad"}}
+
+// CHECK-NEXT: ->(plugin:[[#PID2:]]) {"getCapability":{"capability":{"protocolVersion":[[#PROTOCOL_VERSION]]}}}
+// CHECK-NEXT: <-(plugin:[[#PID2]]) {"getCapabilityResult":{"capability":{"features":["load-plugin-library"],"protocolVersion":[[#PROTOCOL_VERSION]]}}}
+// CHECK-NEXT: ->(plugin:[[#PID2]]) {"loadPluginLibrary":{"libraryPath":"{{.*}}EvilMacros{{.*}},"moduleName":"EvilMacros"}}
+// CHECK-NEXT: <-(plugin:[[#PID2]]) {"loadPluginLibraryResult":{"diagnostics":[],"loaded":true}}
+// CHECK-NEXT: ->(plugin:[[#PID2]]) {"expandFreestandingMacro":{"discriminator":"{{.*}}","lexicalContext":{{.*}},"macro":{"moduleName":"EvilMacros","name":"evil","typeName":"CrashingMacro"}{{.*}}
+
+// CHECK-NEXT: ->(plugin:[[#PID3:]]) {"getCapability":{"capability":{"protocolVersion":[[#PROTOCOL_VERSION]]}}}
+// CHECK-NEXT: <-(plugin:[[#PID3]]) {"getCapabilityResult":{"capability":{"features":["load-plugin-library"],"protocolVersion":[[#PROTOCOL_VERSION]]}}}
+// CHECK-NEXT: ->(plugin:[[#PID3]]) {"loadPluginLibrary":{"libraryPath":"{{.*}}EvilMacros{{.*}}","moduleName":"EvilMacros"}}
+// CHECK-NEXT: <-(plugin:[[#PID3]]) {"loadPluginLibraryResult":{"diagnostics":[],"loaded":true}}
+// CHECK-NEXT: ->(plugin:[[#PID3]]) {"loadPluginLibrary":{"libraryPath":"{{.*}}MacroDefinition{{.*}}","moduleName":"MacroDefinition"}}
+// CHECK-NEXT: <-(plugin:[[#PID3]]) {"loadPluginLibraryResult":{"diagnostics":[],"loaded":true}}
+// CHECK-NEXT: ->(plugin:[[#PID3]]) {"expandFreestandingMacro":{"discriminator":"{{.*}}","lexicalContext":{{.*}},"macro":{"moduleName":"MacroDefinition","name":"stringify","typeName":"StringifyMacro"}{{.*}}
+// CHECK-NEXT: <-(plugin:[[#PID3]]) {"expandMacroResult":{"diagnostics":[],"expandedSource":"(1, \"1\")"}}
+
+//--- MacroDefinition.swift
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import SwiftSyntaxMacros
+
+public struct StringifyMacro: ExpressionMacro {
+  public static func expansion(
+    of macro: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    guard let argument = macro.arguments.first?.expression else {
+      fatalError("boom")
+    }
+
+    return "(\(argument), \(StringLiteralExprSyntax(content: argument.description)))"
+  }
+}
+
+//--- EvilMacros.swift
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import SwiftSyntaxMacros
+
+public struct CrashingMacro: ExpressionMacro {
+  public static func expansion(
+    of macro: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    let arg: UInt = UInt(macro.argumentList.first!.expression.description)!
+    let zero: UInt = 0
+    return "\(raw: zero - arg).description"
+  }
+}
+
+//--- CrashOnLoad.c
+#include <stdlib.h>
+
+__attribute__((constructor))
+void crashMe(void) {
+  abort();
+}
+
+//--- MacroLibrary.swift
+@freestanding(expression) public macro crash() -> Int = #externalMacro(module: "CrashOnLoad", type: "WhateverMacro")
+@freestanding(expression) public macro stringify<T>(_ value: T) -> (T, String) = #externalMacro(module: "MacroDefinition", type: "StringifyMacro")
+@freestanding(expression) public macro evil(_ value: Int) -> String = #externalMacro(module: "EvilMacros", type: "CrashingMacro")
+
+//--- app.swift
+import MacroLibrary 
+
+func test() {
+  _ = #crash() // expected-error {{external macro implementation type 'CrashOnLoad.WhateverMacro' could not be found for macro 'crash()'; failed to load library plugin}}
+  _ = #evil(1) // expected-error {{failed to receive result from plugin (from macro 'evil')}}
+  _ = #stringify(1)
+}