Initial support for generating client and server stubs for Dart.

lib/client_generator.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+part of protoc;
+
+class ClientApiGenerator extends ProtobufContainer {
+  final String classname;
+  final String fqname;
+
+  final ProtobufContainer _parent;
+  final GenerationContext _context;
+  final ServiceDescriptorProto _descriptor;
+
+  ClientApiGenerator(ServiceDescriptorProto descriptor,
+      ProtobufContainer parent, this._context)
+      : _descriptor = descriptor,
+        _parent = parent,
+        classname = descriptor.name,
+        fqname = (parent == null || parent.fqname == null)
+            ? descriptor.name
+            : (parent.fqname == '.'
+                ? '.${descriptor.name}'
+                : '${parent.fqname}.${descriptor.name}') {
+    _context.register(this);
+  }
+
+  String get package => _parent.package;
+
+  String _shortType(String typename) {
+    return typename.substring(typename.lastIndexOf('.')+1);
+  }
+
+  void generate(IndentingWriter out) {
+    out.addBlock('class ${classname}Api {', '}', () {
+      out.println('ProtobufClient _client;');

[Søren Gjesse, 2015/06/24 09:08:02]

We could just make this 'var' then the class name can change... - or put in
RpcClient as we agreed upon.

+      out.println('${classname}Api(this._client);');
+      out.println();
+      for (MethodDescriptorProto m in _descriptor.method) {
+        out.addBlock('Future<${_shortType(m.outputType)}> ${m.name}('
+            'ClientContext ctx, ${_shortType(m.inputType)} request) '
+            'async {', '}', () {
+          out.println(
+              'var resultBytes = await _client.Invoke(ctx, '
+              '\'/${_descriptor.name}.${m.name}\', request.writeToBuffer());');

[skybrian, 2015/06/24 16:16:29]

It seems like ProtobufClient should have the responsibility for constructing
whatever URL it needs, so just pass in the descriptor name and method name as
separate arguments here?

Also, a PbClient might be using JSON instead of a binary transport, so I think
we should pass it two GeneratedMessage instances for the request and response,
and let PbClient do the serialization/deserialization?

(So the only work we're really doing here is calling the appropriate
GeneratedMessage subclass constructor for the response, which would be difficult
for PbClient to do.)

+          out.println('return new ${_shortType(m.outputType)}'
+              '.fromBuffer(resultBytes);');
+        });
+      }
+    });
+    out.println();
+  }
+}