LSP: add convenient log function for a response error

Change-Id: I50c6667af572e7e8133da587c75d3e55a0f2cac4
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/libs/languageserverprotocol/jsonrpcmessages.h

@@ -155,6 +155,8 @@ public:
                 && checkOptional<Error>(error, dataKey);
     }
 
+    QString toString() const { return errorCodesToString(code()) + ": " + message(); }
+
     // predefined error codes
     enum ErrorCodes {
         // Defined by JSON RPC
@@ -320,8 +322,6 @@ template <typename Error>
 inline QDebug operator<<(QDebug stream,
                 const LanguageServerProtocol::ResponseError<Error> &error)
 {
-    stream.nospace() << LanguageServerProtocol::ResponseError<Error>::errorCodesToString(error.code())
-                     << ":"
-                     << error.message();
+    stream.nospace() << error.toString();
     return stream;
 }

src/plugins/languageclient/baseclient.h

@@ -120,6 +120,10 @@ public:
 
     void log(const QString &message,
              Core::MessageManager::PrintToOutputPaneFlag flag = Core::MessageManager::NoModeSwitch);
+    template<typename Error>
+    void log(const LanguageServerProtocol::ResponseError<Error> &responseError,
+             Core::MessageManager::PrintToOutputPaneFlag flag = Core::MessageManager::NoModeSwitch)
+    { log(responseError.toString(), flag); }
 
 signals:
     void initialized(LanguageServerProtocol::ServerCapabilities capabilities);

src/plugins/languageclient/languageclientcodeassist.cpp

@@ -350,7 +350,7 @@ void LanguageClientCompletionAssistProcessor::handleCompletionResponse(
     m_running = false;
     QTC_ASSERT(m_client, return);
     if (auto error = response.error()) {
-        m_client->log(error.value().message());
+        m_client->log(error.value());
         return;
     }
     const Utils::optional<CompletionResult> &result = response.result();