pkg/docgen: support better const rendering of String, List, and empty Map

pkg/docgen/test/constant_argument_test.dart

Index: pkg/docgen/test/constant_argument_test.dart
diff --git a/pkg/docgen/test/typedef_test.dart b/pkg/docgen/test/constant_argument_test.dart
similarity index 51%
copy from pkg/docgen/test/typedef_test.dart
copy to pkg/docgen/test/constant_argument_test.dart
index 9911f0852193d75afc4c54d23cc298ab5a67817f..ca735f4781e98c4faa69cfa0c537039fff092dfe 100644
--- a/pkg/docgen/test/typedef_test.dart
+++ b/pkg/docgen/test/constant_argument_test.dart
@@ -20,7 +20,7 @@ void main() {
     scheduleTempDir();
   });
 
-  test('typedef gen', () {
+  test('argument default values', () {
     schedule(() {
       var codeDir = getMultiLibraryCodePath();
       expect(FileSystemEntity.isDirectorySync(codeDir), isTrue);
@@ -28,7 +28,7 @@ void main() {
     });
 
     schedule(() {
-      var path = p.join(d.defaultRoot, 'docs', 'test_lib-bar.json');
+      var path = p.join(d.defaultRoot, 'docs', 'test_lib.json');
       var dartCoreJson = new File(path).readAsStringSync();
 
       var testLibBar = JSON.decode(dartCoreJson) as Map<String, dynamic>;
@@ -36,30 +36,27 @@ void main() {
       //
       // Validate function doc references
       //
-      var generateFoo = testLibBar['functions']['methods']['generateFoo']
+      var functionDef =
+          testLibBar['functions']['methods']['positionalDefaultValues']
           as Map<String, dynamic>;
 
-      expect(generateFoo['comment'], '<p><a>test_lib-bar.generateFoo.input</a> '
-          'is of type <a>test_lib-bar.C</a> returns an <a>test_lib.A</a>.</p>');
+      var params = functionDef['parameters'] as Map<String, dynamic>;
 
-      var classes = testLibBar['classes'] as Map<String, dynamic>;
-
-      expect(classes, hasLength(3));
-
-      expect(classes['class'], isList);
-      expect(classes['error'], isList);
-
-      var typeDefs = classes['typedef'] as Map<String, dynamic>;
-      var comparator = typeDefs['AnATransformer'] as Map<String, dynamic>;
-
-      var expectedPreview = '<p>Processes a [C] instance for testing.</p>';
-
-      expect(comparator['preview'], expectedPreview);
-
-      var expectedComment = expectedPreview + '\n'
-          '<p>To eliminate import warnings for [A] and to test typedefs.</p>';
-
-      expect(comparator['comment'], expectedComment);
+      var vals = {};
+      params.forEach((paramName, paramHash) {
+        expect(_PARAM_VALUES, contains(paramName));
+        expect(paramHash['value'], _PARAM_VALUES[paramName],
+            reason: 'Value for $paramName should match expected');
+      });
     });
   });
 }
+
+final _PARAM_VALUES = {
+  "boolConst": "true",
+  "intConst": "42",
+  "listConst": '[true, 42, "Shanna", null, 3.14, []]',
+  "mapConst": startsWith("Map"),
+  "emptyMap": '{}',
+  "stringConst": "\"Shanna\""
+};