diff --git a/pkgs/_analyzer_macros/lib/query_service.dart b/pkgs/_analyzer_macros/lib/query_service.dart
index f7cd94f8..e3199ec4 100644
--- a/pkgs/_analyzer_macros/lib/query_service.dart
+++ b/pkgs/_analyzer_macros/lib/query_service.dart
@@ -20,7 +20,7 @@ analyzer.LinkedElementFactory get _elementFactory =>
 class AnalyzerQueryService implements QueryService {
   @override
   Future<QueryResponse> handle(QueryRequest request) async {
-    return QueryResponse(model: _evaluateClassQuery(request.query.target));
+    return QueryResponse(model: _evaluateClassQuery(request.query!.target!));
   }
 
   Model _evaluateClassQuery(QualifiedName target) {
diff --git a/pkgs/_cfe_macros/lib/query_service.dart b/pkgs/_cfe_macros/lib/query_service.dart
index 9fec81a4..6ef38614 100644
--- a/pkgs/_cfe_macros/lib/query_service.dart
+++ b/pkgs/_cfe_macros/lib/query_service.dart
@@ -15,7 +15,7 @@ class CfeQueryService implements QueryService {
   @override
   Future<QueryResponse> handle(QueryRequest request) async {
     return QueryResponse(
-        model: await _evaluateClassQuery(request.query.target));
+        model: await _evaluateClassQuery(request.query!.target!));
   }
 
   Future<Model> _evaluateClassQuery(QualifiedName target) async {
diff --git a/pkgs/_macro_client/lib/macro_client.dart b/pkgs/_macro_client/lib/macro_client.dart
index 45628800..f08274c1 100644
--- a/pkgs/_macro_client/lib/macro_client.dart
+++ b/pkgs/_macro_client/lib/macro_client.dart
@@ -30,7 +30,8 @@ class MacroClient {
     // Tell the host which macros are in this bundle.
     for (final macro in macros) {
       _sendRequest(MacroRequest.macroStartedRequest(
-          MacroStartedRequest(macroDescription: macro.description)));
+          MacroStartedRequest(macroDescription: macro.description),
+          id: nextRequestId));
     }
 
     const Utf8Decoder()
@@ -64,7 +65,8 @@ class MacroClient {
     switch (hostRequest.type) {
       case HostRequestType.augmentRequest:
         _sendResponse(Response.augmentResponse(
-            await macros.single.augment(_host, hostRequest.asAugmentRequest)));
+            await macros.single.augment(_host, hostRequest.asAugmentRequest),
+            requestId: hostRequest.id));
       default:
       // Ignore unknown request.
       // TODO(davidmorgan): make handling of unknown request types a designed
@@ -96,7 +98,8 @@ class RemoteMacroHost implements Host {
 
   @override
   Future<Model> query(Query query) async {
-    _client._sendRequest(MacroRequest.queryRequest(QueryRequest(query: query)));
+    _client._sendRequest(MacroRequest.queryRequest(QueryRequest(query: query),
+        id: nextRequestId));
     // TODO(davidmorgan): this is needed because the constructor doesn't wait
     // for responses to `MacroStartedRequest`, so we need to discard the
     // responses. Properly track requests and responses.
@@ -105,7 +108,7 @@ class RemoteMacroHost implements Host {
       if (nextResponse.type == ResponseType.macroStartedResponse) {
         continue;
       }
-      return nextResponse.asQueryResponse.model;
+      return nextResponse.asQueryResponse.model!;
     }
   }
 
diff --git a/pkgs/_macro_client/test/macro_client_test.dart b/pkgs/_macro_client/test/macro_client_test.dart
index 05cc1fe3..c3f0645d 100644
--- a/pkgs/_macro_client/test/macro_client_test.dart
+++ b/pkgs/_macro_client/test/macro_client_test.dart
@@ -45,13 +45,15 @@ void main() {
           '{"type":"MacroStartedRequest","value":'
           '{"macroDescription":{"runsInPhases":[2]}}}');
 
-      socket.writeln(
-          json.encode(HostRequest.augmentRequest(AugmentRequest(phase: 2))));
+      var requestId = nextRequestId;
+      socket.writeln(json.encode(
+          HostRequest.augmentRequest(AugmentRequest(phase: 2), id: requestId)));
       final augmentResponse = await responses.next;
       expect(
           augmentResponse,
           '{"type":"AugmentResponse","value":'
-          '{"augmentations":[{"code":"int get x => 3;"}]}}');
+          '{"augmentations":[{"code":"int get x => 3;"}]},'
+          '"requestId":$requestId}');
     });
 
     test('sends query requests to host, sends reponse', () async {
@@ -73,23 +75,30 @@ void main() {
           '{"type":"MacroStartedRequest","value":'
           '{"macroDescription":{"runsInPhases":[3]}}}');
 
-      socket.writeln(json.encode(HostRequest.augmentRequest(AugmentRequest(
-          phase: 3, target: QualifiedName('package:foo/foo.dart#Foo')))));
+      var requestId = nextRequestId;
+      socket.writeln(json.encode(HostRequest.augmentRequest(
+          AugmentRequest(
+              phase: 3, target: QualifiedName('package:foo/foo.dart#Foo')),
+          id: nextRequestId)));
       final queryRequest = await responses.next;
       expect(
         queryRequest,
         '{"type":"QueryRequest","value":'
-        '{"query":{"target":"package:foo/foo.dart#Foo"}}}',
+        '{"query":{"target":"package:foo/foo.dart#Foo"}},'
+        '"id":$requestId}',
       );
 
-      socket.writeln(json.encode(Response.queryResponse(QueryResponse(
-          model: Model(uris: {'package:foo/foo.dart': Library()})))));
+      socket.writeln(json.encode(Response.queryResponse(
+          QueryResponse(
+              model: Model(uris: {'package:foo/foo.dart': Library()})),
+          requestId: requestId)));
 
       final augmentRequest = await responses.next;
       expect(
         augmentRequest,
         '{"type":"AugmentResponse","value":'
-        '{"augmentations":[{"code":"// {\\"uris\\":{\\"package:foo/foo.dart\\":{}}}"}]}}',
+        '{"augmentations":[{"code":"// {\\"uris\\":{\\"package:foo/foo.dart\\":{}}}"}]},'
+        '"requestId":$requestId}',
       );
     });
   });
diff --git a/pkgs/_macro_host/lib/macro_host.dart b/pkgs/_macro_host/lib/macro_host.dart
index 4ebfe1ea..6c804106 100644
--- a/pkgs/_macro_host/lib/macro_host.dart
+++ b/pkgs/_macro_host/lib/macro_host.dart
@@ -67,7 +67,7 @@ class MacroHost {
     // TODO(davidmorgan): this just assumes the macro is running, actually
     // track macro lifecycle.
     final response = await macroServer.sendToMacro(
-        name, HostRequest.augmentRequest(request));
+        name, HostRequest.augmentRequest(request, id: nextRequestId));
     return response.asAugmentResponse;
   }
 }
@@ -88,12 +88,15 @@ class _HostService implements HostService {
         _macroPhases!.complete(request
             .asMacroStartedRequest.macroDescription.runsInPhases
             .toSet());
-        return Response.macroStartedResponse(MacroStartedResponse());
+        return Response.macroStartedResponse(MacroStartedResponse(),
+            requestId: request.id);
       case MacroRequestType.queryRequest:
         return Response.queryResponse(
-            await queryService.handle(request.asQueryRequest));
+            await queryService.handle(request.asQueryRequest),
+            requestId: request.id);
       default:
-        return Response.errorResponse(ErrorResponse(error: 'unsupported'));
+        return Response.errorResponse(ErrorResponse(error: 'unsupported'),
+            requestId: request.id);
     }
   }
 }
diff --git a/pkgs/_macro_server/test/macro_server_test.dart b/pkgs/_macro_server/test/macro_server_test.dart
index a2b5ff40..41a501a2 100644
--- a/pkgs/_macro_server/test/macro_server_test.dart
+++ b/pkgs/_macro_server/test/macro_server_test.dart
@@ -36,8 +36,10 @@ class TestHostService implements HostService {
   Future<Response> handle(MacroRequest request) async {
     if (request.type == MacroRequestType.macroStartedRequest) {
       _macroStartedRequestsController.add(request.asMacroStartedRequest);
-      return Response.macroStartedResponse(MacroStartedResponse());
+      return Response.macroStartedResponse(MacroStartedResponse(),
+          requestId: request.id);
     }
-    return Response.errorResponse(ErrorResponse(error: 'unimplemented'));
+    return Response.errorResponse(ErrorResponse(error: 'unimplemented'),
+        requestId: request.id);
   }
 }
diff --git a/pkgs/dart_model/lib/src/dart_model.g.dart b/pkgs/dart_model/lib/src/dart_model.g.dart
index cfd82b12..6e1e7c7c 100644
--- a/pkgs/dart_model/lib/src/dart_model.g.dart
+++ b/pkgs/dart_model/lib/src/dart_model.g.dart
@@ -1,5 +1,5 @@
 // This file is generated. To make changes edit schemas/*.schema.json
-// then run from the repo root: dart tool/model_generator/bin/main.dart
+// then run from the repo root: dart tool/dart_model_generator/bin/main.dart
 
 /// An augmentation to Dart code. TODO(davidmorgan): this is a placeholder.
 extension type Augmentation.fromJson(Map<String, Object?> node) {
@@ -165,12 +165,19 @@ enum StaticTypeType {
 }
 
 extension type StaticType.fromJson(Map<String, Object?> node) {
-  static StaticType neverType(NeverType neverType) =>
-      StaticType.fromJson({'type': 'NeverType', 'value': null});
+  static StaticType neverType(NeverType neverType) => StaticType.fromJson({
+        'type': 'NeverType',
+        'value': neverType,
+      });
   static StaticType nullableType(NullableType nullableType) =>
-      StaticType.fromJson({'type': 'NullableType', 'value': nullableType.node});
-  static StaticType voidType(VoidType voidType) =>
-      StaticType.fromJson({'type': 'VoidType', 'value': voidType.string});
+      StaticType.fromJson({
+        'type': 'NullableType',
+        'value': nullableType,
+      });
+  static StaticType voidType(VoidType voidType) => StaticType.fromJson({
+        'type': 'VoidType',
+        'value': voidType,
+      });
   StaticTypeType get type {
     switch (node['type'] as String) {
       case 'NeverType':
diff --git a/pkgs/macro_service/lib/src/macro_service.dart b/pkgs/macro_service/lib/src/macro_service.dart
index 5b6725ab..16b854eb 100644
--- a/pkgs/macro_service/lib/src/macro_service.dart
+++ b/pkgs/macro_service/lib/src/macro_service.dart
@@ -18,3 +18,20 @@ abstract interface class MacroService {
   /// Handles [request].
   Future<Response> handle(HostRequest request);
 }
+
+/// Shared implementation of auto incrementing 32 bit IDs.
+///
+/// These roll back to 0 once it is greater than 2^32.
+///
+/// These are only unique to the process which generates the request,
+/// so for instance the host and macro services may generate conflicting ids
+/// and that is allowed.
+int get nextRequestId {
+  final next = _nextRequestId++;
+  if (_nextRequestId > 2 ^ 32) {
+    _nextRequestId = 0;
+  }
+  return next;
+}
+
+int _nextRequestId = 0;
diff --git a/pkgs/macro_service/lib/src/macro_service.g.dart b/pkgs/macro_service/lib/src/macro_service.g.dart
index 8c3d8371..80cd4678 100644
--- a/pkgs/macro_service/lib/src/macro_service.g.dart
+++ b/pkgs/macro_service/lib/src/macro_service.g.dart
@@ -1,5 +1,5 @@
 // This file is generated. To make changes edit schemas/*.schema.json
-// then run from the repo root: dart tool/model_generator/bin/main.dart
+// then run from the repo root: dart tool/dart_model_generator/bin/main.dart
 
 import 'package:dart_model/dart_model.dart';
 
@@ -66,9 +66,15 @@ enum HostRequestType {
 }
 
 extension type HostRequest.fromJson(Map<String, Object?> node) {
-  static HostRequest augmentRequest(AugmentRequest augmentRequest) =>
-      HostRequest.fromJson(
-          {'type': 'AugmentRequest', 'value': augmentRequest.node});
+  static HostRequest augmentRequest(
+    AugmentRequest augmentRequest, {
+    required int id,
+  }) =>
+      HostRequest.fromJson({
+        'type': 'AugmentRequest',
+        'value': augmentRequest,
+        'id': id,
+      });
   HostRequestType get type {
     switch (node['type'] as String) {
       case 'AugmentRequest':
@@ -84,6 +90,9 @@ extension type HostRequest.fromJson(Map<String, Object?> node) {
     }
     return AugmentRequest.fromJson(node['value'] as Map<String, Object?>);
   }
+
+  /// The id of this request, must be returned in responses.
+  int get id => node['id'] as int;
 }
 
 /// Information about a macro that the macro provides to the host.
@@ -125,12 +134,23 @@ enum MacroRequestType {
 
 extension type MacroRequest.fromJson(Map<String, Object?> node) {
   static MacroRequest macroStartedRequest(
-          MacroStartedRequest macroStartedRequest) =>
-      MacroRequest.fromJson(
-          {'type': 'MacroStartedRequest', 'value': macroStartedRequest.node});
-  static MacroRequest queryRequest(QueryRequest queryRequest) =>
-      MacroRequest.fromJson(
-          {'type': 'QueryRequest', 'value': queryRequest.node});
+    MacroStartedRequest macroStartedRequest, {
+    required int id,
+  }) =>
+      MacroRequest.fromJson({
+        'type': 'MacroStartedRequest',
+        'value': macroStartedRequest,
+        'id': id,
+      });
+  static MacroRequest queryRequest(
+    QueryRequest queryRequest, {
+    required int id,
+  }) =>
+      MacroRequest.fromJson({
+        'type': 'QueryRequest',
+        'value': queryRequest,
+        'id': id,
+      });
   MacroRequestType get type {
     switch (node['type'] as String) {
       case 'MacroStartedRequest':
@@ -155,6 +175,9 @@ extension type MacroRequest.fromJson(Map<String, Object?> node) {
     }
     return QueryRequest.fromJson(node['value'] as Map<String, Object?>);
   }
+
+  /// The id of this request, must be returned in responses.
+  int get id => node['id'] as int;
 }
 
 /// Macro's query about the code it should augment.
@@ -189,17 +212,42 @@ enum ResponseType {
 }
 
 extension type Response.fromJson(Map<String, Object?> node) {
-  static Response augmentResponse(AugmentResponse augmentResponse) =>
-      Response.fromJson(
-          {'type': 'AugmentResponse', 'value': augmentResponse.node});
-  static Response errorResponse(ErrorResponse errorResponse) =>
-      Response.fromJson({'type': 'ErrorResponse', 'value': errorResponse.node});
+  static Response augmentResponse(
+    AugmentResponse augmentResponse, {
+    required int requestId,
+  }) =>
+      Response.fromJson({
+        'type': 'AugmentResponse',
+        'value': augmentResponse,
+        'requestId': requestId,
+      });
+  static Response errorResponse(
+    ErrorResponse errorResponse, {
+    required int requestId,
+  }) =>
+      Response.fromJson({
+        'type': 'ErrorResponse',
+        'value': errorResponse,
+        'requestId': requestId,
+      });
   static Response macroStartedResponse(
-          MacroStartedResponse macroStartedResponse) =>
-      Response.fromJson(
-          {'type': 'MacroStartedResponse', 'value': macroStartedResponse.node});
-  static Response queryResponse(QueryResponse queryResponse) =>
-      Response.fromJson({'type': 'QueryResponse', 'value': queryResponse.node});
+    MacroStartedResponse macroStartedResponse, {
+    required int requestId,
+  }) =>
+      Response.fromJson({
+        'type': 'MacroStartedResponse',
+        'value': macroStartedResponse,
+        'requestId': requestId,
+      });
+  static Response queryResponse(
+    QueryResponse queryResponse, {
+    required int requestId,
+  }) =>
+      Response.fromJson({
+        'type': 'QueryResponse',
+        'value': queryResponse,
+        'requestId': requestId,
+      });
   ResponseType get type {
     switch (node['type'] as String) {
       case 'AugmentResponse':
@@ -242,4 +290,7 @@ extension type Response.fromJson(Map<String, Object?> node) {
     }
     return QueryResponse.fromJson(node['value'] as Map<String, Object?>);
   }
+
+  /// The id of the [AugmentRequest] this is responding to.
+  int get requestId => node['requestId'] as int;
 }
diff --git a/schemas/macro_service.schema.json b/schemas/macro_service.schema.json
index a182795a..09d1dc17 100644
--- a/schemas/macro_service.schema.json
+++ b/schemas/macro_service.schema.json
@@ -62,6 +62,10 @@
     "HostRequest": {
       "$description": "A request sent from host to macro.",
       "properties": {
+        "id": {
+          "description": "The id of this request, must be returned in responses.",
+          "type": "integer"
+        },
         "type": {
           "type": "string"
         },
@@ -72,7 +76,12 @@
             }
           ]
         }
-      }
+      },
+      "required": [
+        "id",
+        "type",
+        "value"
+      ]
     },
     "MacroDescription": {
       "type": "object",
@@ -103,6 +112,10 @@
     "MacroRequest": {
       "$description": "A request sent from macro to host.",
       "properties": {
+        "id": {
+          "description": "The id of this request, must be returned in responses.",
+          "type": "integer"
+        },
         "type": {
           "type": "string"
         },
@@ -116,7 +129,12 @@
             }
           ]
         }
-      }
+      },
+      "required": [
+        "id",
+        "type",
+        "value"
+      ]
     },
     "QueryRequest": {
       "type": "object",
@@ -139,6 +157,10 @@
     "Response": {
       "$description": "A response to a [MacroRequest] or [HostRequest].",
       "properties": {
+        "requestId": {
+          "description": "The id of the [AugmentRequest] this is responding to.",
+          "type": "integer"
+        },
         "type": {
           "type": "string"
         },
@@ -158,7 +180,12 @@
             }
           ]
         }
-      }
+      },
+      "required": [
+        "requestId",
+        "type",
+        "value"
+      ]
     }
   }
 }
diff --git a/tool/dart_model_generator/lib/generate_dart_model.dart b/tool/dart_model_generator/lib/generate_dart_model.dart
index aa1ab901..7deb9fcb 100644
--- a/tool/dart_model_generator/lib/generate_dart_model.dart
+++ b/tool/dart_model_generator/lib/generate_dart_model.dart
@@ -26,11 +26,13 @@ void run() {
 
 /// Generates and returns code for [schemaJson].
 String generate(String schemaJson,
-    {bool importDartModel = false, String? dartModelJson}) {
+    {bool importDartModel = false,
+    bool importMacroService = false,
+    String? dartModelJson}) {
   final result = <String>[
     '// This file is generated. To make changes edit schemas/*.schema.json',
     '// then run from the repo root: '
-        'dart tool/model_generator/bin/main.dart',
+        'dart tool/dart_model_generator/bin/main.dart',
     '',
     if (importDartModel) "import 'package:dart_model/dart_model.dart';",
   ];
@@ -45,7 +47,7 @@ String generate(String schemaJson,
     if (_isUnion(value)) {
       result.add(_generateUnion(
         key,
-        value.properties['value']!.oneOf,
+        value,
         allDefinitions: allDefinitions,
       ));
     } else {
@@ -108,22 +110,11 @@ String _generateExtensionType(String name, JsonSchema definition) {
       } else {
         result.writeln('  $name({');
         for (final property in propertyMetadatas) {
-          result.writeln(switch (property.type) {
-            PropertyType.object =>
-              '${property.elementTypeName}? ${property.name},',
-            PropertyType.bool => 'bool? ${property.name},',
-            PropertyType.string => 'String? ${property.name},',
-            PropertyType.integer => 'int? ${property.name},',
-            PropertyType.list =>
-              'List<${property.elementTypeName}>? ${property.name},',
-            PropertyType.map =>
-              'Map<String, ${property.elementTypeName}>? ${property.name},',
-          });
+          result.writeParameter(property, definition);
         }
         result.writeln('}) : this.fromJson({');
         for (final property in propertyMetadatas) {
-          result.writeln('if (${property.name} != null) '
-              "'${property.name}': ${property.name},");
+          result.writeMapElement(property, definition);
         }
         result.writeln('});');
       }
@@ -135,33 +126,8 @@ String _generateExtensionType(String name, JsonSchema definition) {
       throw UnsupportedError('Unsupported type: ${definition.type}');
   }
 
-  // Generate a getter for every field that looks up in the JSON and "creates"
-  // extension types or casts collections as needed. The getters assume the
-  // data is present and will throw if it's not.
   for (final property in propertyMetadatas) {
-    if (property.description != null) {
-      result.writeln('/// ${property.description}');
-    }
-    result.writeln(switch (property.type) {
-      PropertyType.object =>
-        // TODO(davidmorgan): use the extension type constructor instead of
-        // casting.
-        '${property.elementTypeName} get ${property.name} => '
-            'node[\'${property.name}\'] '
-            'as ${property.elementTypeName};',
-      PropertyType.bool => 'bool get ${property.name} => '
-          'node[\'${property.name}\'] as bool;',
-      PropertyType.string => 'String get ${property.name} => '
-          'node[\'${property.name}\'] as String;',
-      PropertyType.integer => 'int get ${property.name} => '
-          'node[\'${property.name}\'] as int;',
-      PropertyType.list =>
-        'List<${property.elementTypeName}> get ${property.name} => '
-            '(node[\'${property.name}\'] as List).cast();',
-      PropertyType.map =>
-        'Map<String, ${property.elementTypeName}> get ${property.name} => '
-            '(node[\'${property.name}\'] as Map).cast();',
-    });
+    result.writePropertyGetter(property);
   }
   result.writeln('}');
   return result.toString();
@@ -175,7 +141,7 @@ bool _isUnion(JsonSchema schema) =>
     schema.properties['type']?.schemaMap!['type'] == 'string' &&
     schema.properties['value']?.oneOf != null;
 
-/// Generates a type called [name] that is a union of the specified [oneOf]
+/// Generates a type called [name] that is a union of the specified `oneOf`
 /// types, which must all be `$ref`s to class definitions.
 ///
 /// An enum is generated next to it called `${name}Type` with one value for
@@ -184,12 +150,14 @@ bool _isUnion(JsonSchema schema) =>
 /// The union type has a `type` getter that returns an instance of this enum,
 /// and `asFoo` getters that "cast" to each type.
 ///
-/// On the wire the union type is: `{"type": <name>, "value": <value>}`
+/// On the wire the union type is: `{"type": <name>, "value": <value>}` and
+/// may have additional properties as well.
 String _generateUnion(
   String name,
-  List<JsonSchema> oneOf, {
+  JsonSchema definition, {
   required Map<String, JsonSchema> allDefinitions,
 }) {
+  final oneOf = definition.properties['value']!.oneOf;
   final result = StringBuffer();
   final unionEntries = oneOf
       .map((s) => _refName(s.schemaMap![r'$ref'] as String))
@@ -205,15 +173,33 @@ String _generateUnion(
     ..writeln('bool get isKnown => this != _unknown;')
     ..writeln('}');
 
+  final extraPropertyMetadatas = [
+    for (var MapEntry(:key, :value) in definition.properties.entries)
+      // These are handled specially for union types.
+      if (key != 'type' && key != 'value') _readPropertyMetadata(key, value)
+  ];
+
   // TODO(davidmorgan): add description.
   result.writeln('extension type $name.fromJson(Map<String, Object?> node) {');
-  for (final (type, def) in unionEntries) {
+  for (final (type, _) in unionEntries) {
     final lowerType = _firstToLowerCase(type);
+    result.writeln('static $name $lowerType($type $lowerType');
+    if (extraPropertyMetadatas.isNotEmpty) {
+      result.writeln(', {');
+      for (final property in extraPropertyMetadatas) {
+        result.writeParameter(property, definition);
+      }
+      result.write('}');
+    }
     result
-      ..writeln('static $name $lowerType($type $lowerType) =>')
+      ..writeln(') =>')
       ..writeln('$name.fromJson({')
       ..writeln("'type': '$type',")
-      ..writeln("'value': ${_dartWrapperToJson(lowerType, def)}});");
+      ..writeln("'value': $lowerType,");
+    for (final property in extraPropertyMetadatas) {
+      result.writeMapElement(property, definition);
+    }
+    result.writeln('});');
   }
 
   result
@@ -237,6 +223,11 @@ String _generateUnion(
           "return $type.fromJson(node['value'] as ${_dartJsonType(schema)});")
       ..writeln('}');
   }
+
+  for (final property in extraPropertyMetadatas) {
+    result.writePropertyGetter(property);
+  }
+
   result.writeln('}');
 
   return result.toString();
@@ -361,3 +352,65 @@ class LocalRefProvider implements RefProvider<SyncJsonProvider> {
         return json.decode(dartModelJson) as Map<String, Object?>;
       };
 }
+
+extension on StringBuffer {
+  void writeType(PropertyMetadata property, {bool nullable = false}) {
+    write(switch (property.type) {
+      PropertyType.object => property.elementTypeName,
+      PropertyType.bool => 'bool',
+      PropertyType.string => 'String',
+      PropertyType.integer => 'int',
+      PropertyType.list => 'List<${property.elementTypeName}>',
+      PropertyType.map => 'Map<String, ${property.elementTypeName}>',
+    });
+    if (nullable) write('?');
+  }
+
+  /// Writes a map element for [property], assuming there is a variable in
+  /// scope with the same name (usually, a function parameter).
+  ///
+  /// If the property is not required, the element will be omitted if the
+  /// variable is null.
+  void writeMapElement(PropertyMetadata property, JsonSchema schema) {
+    if (!schema.propertyRequired(property.name)) {
+      write('if (${property.name} != null) ');
+    }
+    writeln("'${property.name}': ${property.name},");
+  }
+
+  /// Writes a named function parameter for [property].
+  ///
+  /// If the property is required, it will be non-nullable and marked as
+  /// `required`, otherwise it will be nullable and optional.
+  void writeParameter(PropertyMetadata property, JsonSchema schema) {
+    var required = schema.propertyRequired(property.name);
+    if (required) write('required ');
+    writeType(property, nullable: !required);
+    writeln(' ${property.name},');
+  }
+
+  /// Writes a getter for [property] that looks up in the JSON and "creates"
+  /// extension types or casts collections as needed. The getters assume the
+  /// data is present and will throw if it's not, and return types are always
+  /// non-nullable.
+  void writePropertyGetter(PropertyMetadata property) {
+    if (property.description != null) {
+      writeln('/// ${property.description}');
+    }
+    writeType(property);
+    write(' get ${property.name} => ');
+    switch (property.type) {
+      case PropertyType.object ||
+            PropertyType.bool ||
+            PropertyType.string ||
+            PropertyType.integer:
+        write("node['${property.name}'] as ");
+        writeType(property);
+      case PropertyType.list:
+        write("(node['${property.name}'] as List).cast()");
+      case PropertyType.map:
+        write("(node['${property.name}'] as Map).cast()");
+    }
+    writeln(';');
+  }
+}