Introduce operator+= to simplify response creation.

src/server/internalServer.cpp

@@ -683,20 +683,17 @@ std::unique_ptr<Response> InternalServer::handle_search(const RequestContext& re
     } catch(std::runtime_error& e) {
       // Searcher->search will throw a runtime error if there is no valid xapian database to do the search.
       // (in case of zim file not containing a index)
-      auto response = std::move(
-          HTTPErrorHtmlResponse(*this, request, MHD_HTTP_NOT_FOUND,
-                                "fulltext-search-unavailable",
-                                "404-page-heading",
-                                m_root + "/skin/search_results.css")
-        + nonParameterizedMessage("no-search-results")
-      );
+      HTTPErrorHtmlResponse response(*this, request, MHD_HTTP_NOT_FOUND,
+                                     "fulltext-search-unavailable",
+                                     "404-page-heading",
+                                     m_root + "/skin/search_results.css");
+      response += nonParameterizedMessage("no-search-results");
       if(bookIds.size() == 1) {
         auto bookId = *bookIds.begin();
         auto bookName = mp_nameMapper->getNameForId(bookId);
-        return response + TaskbarInfo(bookName, mp_library->getArchiveById(bookId).get());
-      } else {
-        return response;
+        response += TaskbarInfo(bookName, mp_library->getArchiveById(bookId).get());
       }
+      return response;
     }
 
     auto start = 0;

src/server/internalServer.h

@@ -148,7 +148,9 @@ class InternalServer {
 
     bool etag_not_needed(const RequestContext& r) const;
     ETag get_matching_if_none_match_etag(const RequestContext& request) const;
-    Library::BookIdSet selectBooks(const RequestContext& r, const std::string& prefix) const;
+    Library::
+
+    BookIdSet selectBooks(const RequestContext& r, const std::string& prefix) const;
     SearchInfo getSearchInfo(const RequestContext& r, const std::string& prefix) const;
 
   private: // data

src/server/response.cpp

@@ -150,6 +150,12 @@ HTTPErrorHtmlResponse& HTTPErrorHtmlResponse::operator+(const ParameterizedMessa
   return *this + details.getText(m_request.get_user_language());
 }
 
+HTTPErrorHtmlResponse& HTTPErrorHtmlResponse::operator+=(const ParameterizedMessage& details)
+{
+  // operator+() is already a state-modifying operator (akin to operator+=)
+  return *this + details;
+}
+
 
 HTTP400HtmlResponse::HTTP400HtmlResponse(const InternalServer& server,
                                          const RequestContext& request)
@@ -202,6 +208,13 @@ ContentResponseBlueprint& ContentResponseBlueprint::operator+(const TaskbarInfo&
   return *this;
 }
 
+ContentResponseBlueprint& ContentResponseBlueprint::operator+=(const TaskbarInfo& taskbarInfo)
+{
+  // operator+() is already a state-modifying operator (akin to operator+=)
+  return *this + taskbarInfo;
+}
+
+
 std::unique_ptr<Response> Response::build_416(const InternalServer& server, size_t resourceLength)
 {
   auto response = Response::build(server);

src/server/response.h

@@ -168,6 +168,7 @@ class ContentResponseBlueprint
 
 
   ContentResponseBlueprint& operator+(const TaskbarInfo& taskbarInfo);
+  ContentResponseBlueprint& operator+=(const TaskbarInfo& taskbarInfo);
 
 protected: // functions
   std::string getMessage(const std::string& msgId) const;
@@ -193,8 +194,10 @@ struct HTTPErrorHtmlResponse : ContentResponseBlueprint
                       const std::string& cssUrl = "");
 
   using ContentResponseBlueprint::operator+;
+  using ContentResponseBlueprint::operator+=;
   HTTPErrorHtmlResponse& operator+(const std::string& msg);
   HTTPErrorHtmlResponse& operator+(const ParameterizedMessage& errorDetails);
+  HTTPErrorHtmlResponse& operator+=(const ParameterizedMessage& errorDetails);
 };
 
 class UrlNotFoundMsg {};