Support annotations on unnamed libraries; 4.9.0 (#440)

Author: srawlins

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 4.9.0
 
 * Add `Library.generatedByComment` to support emitting 'generated by' comments.
+* Support emitting an unnamed library with annotations.
 
 ## 4.8.0
 

lib/src/emitter.dart

@@ -512,13 +512,16 @@ class DartEmitter extends Object
       }
     }
 
+    for (var a in spec.annotations) {
+      visitAnnotation(a, output);
+    }
     if (spec.name != null) {
-      for (var a in spec.annotations) {
-        visitAnnotation(a, output);
-      }
       output.write('library ${spec.name!};');
     } else if (spec.annotations.isNotEmpty) {
-      throw StateError('a library name is required for annotations');
+      // An explicit _unnamed_ library directive is only required if there are
+      // annotations or doc comments on the library (though doc comments are not
+      // currently supported in code_builder).
+      output.write('library;');
     }
 
     final directives = <Directive>[...allocator.imports, ...spec.directives];

test/specs/library_test.dart

@@ -277,17 +277,19 @@ void main() {
       );
     });
 
-    test('should error on unnamed library with annotations', () {
+    test('should emit an unnamed library source file with annotations', () {
       expect(
-        () {
-          Library(
-            (b) => b
-              ..annotations.add(
-                refer('JS', 'package:js/js.dart').call([]),
-              ),
-          ).accept(DartEmitter());
-        },
-        throwsStateError,
+        Library(
+          (b) => b
+            ..annotations.add(
+              refer('JS', 'package:js/js.dart').call([]),
+            ),
+        ),
+        equalsDart(r'''
+          @JS()
+          library;
+          import 'package:js/js.dart';
+        ''', DartEmitter(allocator: Allocator())),
       );
     });
   });