[cfe] Recognize indirect use of macros

When a macro declaration is supplied as dill, the macro api library
is not directly needed by the source libraries. Therefore, in order
to determine whether macro declarations are available, we need to also
look up the macro api library in the dill loader.

Closes #54560

Change-Id: I131d3881f557566871d9e8c9f38c19029637c534
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/346000
Reviewed-by: Morgan :) <davidmorgan@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Nicholas Shahan <nshahan@google.com>

pkg/dev_compiler/test/macros/macros_test.dart

@@ -7,6 +7,7 @@ import 'dart:io';
 import 'package:_fe_analyzer_shared/src/macros/bootstrap.dart';
 import 'package:_fe_analyzer_shared/src/macros/executor/serialization.dart';
 import 'package:bazel_worker/bazel_worker.dart';
+import 'package:dev_compiler/ddc.dart' as ddc;
 import 'package:frontend_server/compute_kernel.dart';
 import 'package:test/test.dart';
 
@@ -25,6 +26,7 @@ void main() {
     late File bootstrapDillFileDdc;
     late Uri testMacroUri;
     late File packageConfig;
+    late List<String> ddcArgs;
     late List<String> executableArgs;
 
     final applyTestMacroDart = file('apply_test_macro.dart');
@@ -120,12 +122,7 @@ macro class TestMacro implements ClassDeclarationsMacro {
       expect(bootstrapResultDdc.succeeded, true);
 
       // Write source that applies the macro.
-      // TODO(davidmorgan): the `api` import should not be needed, but without
-      // it the macro application does nothing: `computeMacroDeclarations` in
-      // `source_loader.dart` does nothing because
-      // `lookupLibraryBuilder(macroLibraryUri)` returns null. Fix.
       applyTestMacroDart.writeAsStringSync('''
-import 'package:_fe_analyzer_shared/src/macros/api.dart';
 import 'package:test_macro/test_macro.dart';
 
 @TestMacro()
@@ -137,10 +134,7 @@ void main() {
   print(TestClass().x);
 }
 ''');
-
-      executableArgs = [
-        '--enable-experiment=macros',
-        _resolvePath('../../gen/dartdevc.dart.snapshot'),
+      ddcArgs = [
         '--enable-experiment=macros',
         '--sound-null-safety',
         '--dart-sdk-summary',
@@ -148,12 +142,53 @@ void main() {
         '--enable-experiment=macros',
         '--packages=${packageConfig.uri}',
       ];
+
+      executableArgs = [
+        '--enable-experiment=macros',
+        _resolvePath('../../gen/dartdevc.dart.snapshot'),
+        ...ddcArgs
+      ];
     });
 
     tearDown(() {
       if (tmp.existsSync()) tmp.deleteSync(recursive: true);
     });
 
+    test('compile in direct mode', () async {
+      await ddc.internalMain([
+        ...ddcArgs,
+        '--no-source-map',
+        '-o',
+        testMacroJS.path,
+        testMacroDart.path,
+      ]);
+      // TODO(johnniwinther): Is there a way to verify that no errors/warnings
+      // were reported?
+      expect(exitCode, EXIT_CODE_OK);
+
+      expect(testMacroJS.existsSync(), isTrue);
+      expect(testMacroSummary.existsSync(), isTrue);
+
+      await ddc.internalMain([
+        ...ddcArgs,
+        '--precompiled-macro',
+        '${bootstrapDillFileVm.path};$testMacroUri',
+        '--no-source-map',
+        '--no-summarize',
+        '-s',
+        testMacroSummary.path,
+        '-s',
+        bootstrapDillFileDdc.path,
+        '-o',
+        applyTestMacroJS.path,
+        applyTestMacroDart.path,
+      ]);
+      // TODO(johnniwinther): Is there a way to verify that no errors/warnings
+      // were reported?
+      expect(exitCode, EXIT_CODE_OK);
+      expect(applyTestMacroJS.existsSync(), isTrue);
+    });
+
     test('compile in basic mode', () {
       var result = Process.runSync(Platform.executable, [
         ...executableArgs,
@@ -165,6 +200,7 @@ void main() {
       expect(result.stdout, isEmpty);
       expect(result.stderr, isEmpty);
       expect(result.exitCode, EXIT_CODE_OK);
+
       expect(testMacroJS.existsSync(), isTrue);
       expect(testMacroSummary.existsSync(), isTrue);
 

pkg/front_end/lib/src/fasta/source/source_loader.dart

@@ -1515,7 +1515,15 @@ severity: $severity
   /// If no macros need precompilation, `null` is returned.
   NeededPrecompilations? computeMacroDeclarations() {
     LibraryBuilder? macroLibraryBuilder = lookupLibraryBuilder(macroLibraryUri);
-    if (macroLibraryBuilder == null) return null;
+    if (macroLibraryBuilder == null) {
+      // The macro library might not be directly imported by the source
+      // libraries, so we look up in the dill loader as well.
+      macroLibraryBuilder =
+          target.dillTarget.loader.lookupLibraryBuilder(macroLibraryUri);
+      if (macroLibraryBuilder == null) {
+        return null;
+      }
+    }
 
     Builder? macroClassBuilder =
         macroLibraryBuilder.lookupLocalMember(macroClassName);