[Macros] Build and test a macro plugin based on SwiftSyntax

Author: DougGregor

lib/ASTGen/CMakeLists.txt

@@ -121,7 +121,7 @@ if (SWIFT_SWIFT_PARSER)
        OUTPUT_VARIABLE SWIFT_SYNTAX_MODULE_DIRS)
   foreach(module_dir ${SWIFT_SYNTAX_MODULE_DIRS})
     file(GLOB module_files
-         "${SWIFT_SYNTAX_LIBRARIES_SOURCE_DIR}/${module_dir}/*.swift*")
+         "${SWIFT_SYNTAX_LIBRARIES_SOURCE_DIR}/${module_dir}/*.swiftinterface")
     add_custom_command(
       TARGET swiftASTGen PRE_BUILD
       COMMAND ${CMAKE_COMMAND} -E make_directory ${SWIFT_SYNTAX_LIBRARIES_DEST_DIR}/${module_dir}

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -0,0 +1,24 @@
+import SwiftSyntax
+import SwiftSyntaxBuilder
+import _SwiftSyntaxMacros
+
+public struct FileIDMacro: ExpressionMacro {
+  public static func apply(
+    _ macro: MacroExpansionExprSyntax, in context: MacroEvaluationContext
+  ) -> MacroResult<ExprSyntax> {
+    var fileName = context.sourceLocationConverter.location(
+      for: .init(utf8Offset: 0)
+    ).file ?? "<unknown file>"
+
+    // Only keep everything after the last slash.
+    if let lastSlash = fileName.lastIndex(of: "/") {
+      fileName = String(fileName[fileName.index(after: lastSlash)...])
+    }
+
+    let fileLiteral: ExprSyntax = #""\#(context.moduleName)/\#(fileName)""#
+    if let leadingTrivia = macro.leadingTrivia {
+      return MacroResult(fileLiteral.withLeadingTrivia(leadingTrivia))
+    }
+    return MacroResult(fileLiteral)
+  }
+}

test/Macros/macro_external_exec.swift

@@ -0,0 +1,17 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift -Xfrontend -disable-availability-checking -I %swift-host-lib-dir -L %swift-host-lib-dir -emit-library -emit-library-path=%t/%target-library-name(MacroDefinition) -working-directory=%t -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift
+// RUN: %target-build-swift -enable-experimental-feature Macros -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir -L %swift-host-lib-dir %s -o %t/main -module-name MacroUser
+// RUN: %target-run %t/main | %FileCheck %s
+// REQUIRES: executable_test
+
+// FIXME: Swift parser is not enabled on Linux CI yet.
+// REQUIRES: OS=macosx
+
+macro customFileID: String = MacroDefinition.FileIDMacro
+
+func testFunc(a: Int, b: Int) {
+  // CHECK: MacroUser/macro_external_exec.swift
+  print("Result is \(#customFileID)")
+}
+
+testFunc(a: 1, b: 2)