[inspector_protocol] support fall through and moveable Maybe

lib/DispatcherBase_cpp.template

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 //#include "DispatcherBase.h"
 //#include "Parser.h"
 
 {% for namespace in config.protocol.namespace %}
 namespace {{namespace}} {
 {% endfor %}
 
 // static
-const char DispatcherBase::kInvalidRequest[] = "Invalid request";
+DispatchResponse DispatchResponse::OK()
+{
+    DispatchResponse result;
+    result.m_status = kSuccess;
+    result.m_errorCode = kParseError;
+    return result;
+}
+
+// static
+DispatchResponse DispatchResponse::Error(const String& error)
+{
+    DispatchResponse result;
+    result.m_status = kError;
+    result.m_errorCode = kServerError;
+    result.m_errorMessage = error;
+    return result;
+}
+
+// static
+DispatchResponse DispatchResponse::InternalError()
+{
+    DispatchResponse result;
+    result.m_status = kError;
+    result.m_errorCode = kInternalError;
+    result.m_errorMessage = "Internal error";
+    return result;
+}
+
+// static
+DispatchResponse DispatchResponse::FallThrough()
+{
+    DispatchResponse result;
+    result.m_status = kFallThrough;
+    result.m_errorCode = kParseError;
+    return result;
+}
+
+// static
+const char DispatcherBase::kInvalidParamsString[] = "Invalid parameters";
 
 DispatcherBase::WeakPtr::WeakPtr(DispatcherBase* dispatcher) : m_dispatcher(dispatcher) { }
 
 DispatcherBase::WeakPtr::~WeakPtr()
 {
     if (m_dispatcher)
         m_dispatcher->m_weakPtrs.erase(this);
 }
 
 DispatcherBase::Callback::Callback(std::unique_ptr<DispatcherBase::WeakPtr> backendImpl, int callId)
     : m_backendImpl(std::move(backendImpl))
     , m_callId(callId) { }
 
 DispatcherBase::Callback::~Callback() = default;
 
 void DispatcherBase::Callback::dispose()
 {
     m_backendImpl = nullptr;
 }
 
-void DispatcherBase::Callback::sendIfActive(std::unique_ptr<protocol::DictionaryValue> partialMessage, const ErrorString& invocationError)
+void DispatcherBase::Callback::sendIfActive(std::unique_ptr<protocol::DictionaryValue> partialMessage, const DispatchResponse& response)
 {
     if (!m_backendImpl || !m_backendImpl->get())
         return;
-    m_backendImpl->get()->sendResponse(m_callId, invocationError, nullptr, std::move(partialMessage));
+    m_backendImpl->get()->sendResponse(m_callId, response, std::move(partialMessage));
     m_backendImpl = nullptr;
 }
 
 DispatcherBase::DispatcherBase(FrontendChannel* frontendChannel)
     : m_frontendChannel(frontendChannel) { }
 
 DispatcherBase::~DispatcherBase()
 {
     clearFrontend();
 }
 
 // static
 bool DispatcherBase::getCommandName(const String& message, String* result)
 {
     std::unique_ptr<protocol::Value> value = parseJSON(message);
     if (!value)
         return false;
 
     protocol::DictionaryValue* object = DictionaryValue::cast(value.get());
     if (!object)
         return false;
 
     if (!object->getString("method", result))
         return false;
 
     return true;
 }
 
-void DispatcherBase::sendResponse(int callId, const ErrorString& invocationError, ErrorSupport* errors, std::unique_ptr<protocol::DictionaryValue> result)
+void DispatcherBase::sendResponse(int callId, const DispatchResponse& response, std::unique_ptr<protocol::DictionaryValue> result)
 {
-    if (invocationError.length() || (errors && errors->hasErrors())) {
-        reportProtocolError(callId, ServerError, invocationError, errors);
+    if (response.status() == DispatchResponse::kError) {
+        reportProtocolError(callId, response.errorCode(), response.errorMessage(), nullptr);
         return;
     }
 
     std::unique_ptr<protocol::DictionaryValue> responseMessage = DictionaryValue::create();
     responseMessage->setInteger("id", callId);
     responseMessage->setObject("result", std::move(result));
     if (m_frontendChannel)
         m_frontendChannel->sendProtocolResponse(callId, responseMessage->toJSONString());
 }
 
-void DispatcherBase::sendResponse(int callId, const ErrorString& invocationError, std::unique_ptr<protocol::DictionaryValue> result)
+void DispatcherBase::sendResponse(int callId, const DispatchResponse& response)
 {
-    sendResponse(callId, invocationError, nullptr, std::move(result));
+    sendResponse(callId, response, DictionaryValue::create());
 }
 
-void DispatcherBase::sendResponse(int callId, const ErrorString& invocationError)
-{
-    sendResponse(callId, invocationError, nullptr, DictionaryValue::create());
-}
-
-static void reportProtocolErrorTo(FrontendChannel* frontendChannel, int callId, DispatcherBase::CommonErrorCode code, const String& errorMessage, ErrorSupport* errors)
+static void reportProtocolErrorTo(FrontendChannel* frontendChannel, int callId, DispatchResponse::ErrorCode code, const String& errorMessage, ErrorSupport* errors)
 {
     if (!frontendChannel)
         return;
     std::unique_ptr<protocol::DictionaryValue> error = DictionaryValue::create();
     error->setInteger("code", code);
     error->setString("message", errorMessage);
-    DCHECK(error);
     if (errors && errors->hasErrors())
         error->setString("data", errors->errors());
     std::unique_ptr<protocol::DictionaryValue> message = DictionaryValue::create();
     message->setObject("error", std::move(error));
     message->setInteger("id", callId);
     frontendChannel->sendProtocolResponse(callId, message->toJSONString());
 }
 
-void DispatcherBase::reportProtocolError(int callId, CommonErrorCode code, const String& errorMessage, ErrorSupport* errors)
+static void reportProtocolErrorTo(FrontendChannel* frontendChannel, DispatchResponse::ErrorCode code, const String& errorMessage)
+{
+    if (!frontendChannel)
+        return;
+    std::unique_ptr<protocol::DictionaryValue> error = DictionaryValue::create();
+    error->setInteger("code", code);
+    error->setString("message", errorMessage);
+    std::unique_ptr<protocol::DictionaryValue> message = DictionaryValue::create();
+    message->setObject("error", std::move(error));
+    frontendChannel->sendProtocolNotification(message->toJSONString());
+}
+
+void DispatcherBase::reportProtocolError(int callId, DispatchResponse::ErrorCode code, const String& errorMessage, ErrorSupport* errors)
 {
     reportProtocolErrorTo(m_frontendChannel, callId, code, errorMessage, errors);
 }
 
 void DispatcherBase::clearFrontend()
 {
     m_frontendChannel = nullptr;
     for (auto& weak : m_weakPtrs)
         weak->dispose();
     m_weakPtrs.clear();
 }
 
 std::unique_ptr<DispatcherBase::WeakPtr> DispatcherBase::weakPtr()
 {
     std::unique_ptr<DispatcherBase::WeakPtr> weak(new DispatcherBase::WeakPtr(this));
     m_weakPtrs.insert(weak.get());
     return weak;
 }
 
 UberDispatcher::UberDispatcher(FrontendChannel* frontendChannel)
     : m_frontendChannel(frontendChannel) { }
 
 void UberDispatcher::registerBackend(const String& name, std::unique_ptr<protocol::DispatcherBase> dispatcher)
 {
     m_dispatchers[name] = std::move(dispatcher);
 }
 
-void UberDispatcher::dispatch(std::unique_ptr<Value> parsedMessage)
+DispatchResponse::Status UberDispatcher::dispatch(std::unique_ptr<Value> parsedMessage)
 {
-    if (!parsedMessage)
-        return;
+    if (!parsedMessage) {
+        reportProtocolErrorTo(m_frontendChannel, DispatchResponse::kParseError, "Message must be a valid JSON");
+        return DispatchResponse::kError;
+    }
     std::unique_ptr<protocol::DictionaryValue> messageObject = DictionaryValue::cast(std::move(parsedMessage));
-    if (!messageObject)
-        return;
+    if (!messageObject) {
+        reportProtocolErrorTo(m_frontendChannel, DispatchResponse::kInvalidRequest, "Message must be an object");
+        return DispatchResponse::kError;
+    }
 
     int callId = 0;
     protocol::Value* callIdValue = messageObject->get("id");
     bool success = callIdValue && callIdValue->asInteger(&callId);
-    if (!success)
-        return;
+    if (!success) {
+        reportProtocolErrorTo(m_frontendChannel, DispatchResponse::kInvalidRequest, "Message must have integer 'id' porperty");
+        return DispatchResponse::kError;
+    }
 
     protocol::Value* methodValue = messageObject->get("method");
     String method;
     success = methodValue && methodValue->asString(&method);
-    if (!success)
-        return;
+    if (!success) {
+        reportProtocolErrorTo(m_frontendChannel, callId, DispatchResponse::kInvalidRequest, "Message must have string 'method' porperty", nullptr);
+        return DispatchResponse::kError;
+    }
 
     size_t dotIndex = method.find(".");
     if (dotIndex == StringUtil::kNotFound) {
-        reportProtocolErrorTo(m_frontendChannel, callId, DispatcherBase::MethodNotFound, "'" + method + "' wasn't found", nullptr);
-        return;
+        reportProtocolErrorTo(m_frontendChannel, callId, DispatchResponse::kMethodNotFound, "'" + method + "' wasn't found", nullptr);
+        return DispatchResponse::kError;
     }
     String domain = StringUtil::substring(method, 0, dotIndex);
     auto it = m_dispatchers.find(domain);
     if (it == m_dispatchers.end()) {
-        reportProtocolErrorTo(m_frontendChannel, callId, DispatcherBase::MethodNotFound, "'" + method + "' wasn't found", nullptr);
-        return;
+        reportProtocolErrorTo(m_frontendChannel, callId, DispatchResponse::kMethodNotFound, "'" + method + "' wasn't found", nullptr);
+        return DispatchResponse::kError;
     }
-    it->second->dispatch(callId, method, std::move(messageObject));
+    return it->second->dispatch(callId, method, std::move(messageObject));
 }
 
 UberDispatcher::~UberDispatcher() = default;
 
 {% for namespace in config.protocol.namespace %}
 } // namespace {{namespace}}
 {% endfor %}