Remove all the empty “options” members in Column classes

By using SFINAE to use that member only when it exists.

src/database/database.hpp

@@ -20,79 +20,56 @@ class Database
  public:
   using time_point = std::chrono::system_clock::time_point;
 
-  struct Uuid: Column<std::string> { static constexpr auto name = "uuid_";
-    static constexpr auto options = ""; };
+  struct Uuid: Column<std::string> { static constexpr auto name = "uuid_"; };
 
-  struct Owner: Column<std::string> { static constexpr auto name = "owner_";
-    static constexpr auto options = ""; };
+  struct Owner: Column<std::string> { static constexpr auto name = "owner_"; };
 
-  struct IrcChanName: Column<std::string> { static constexpr auto name = "ircChanName_";
-    static constexpr auto options = ""; };
+  struct IrcChanName: Column<std::string> { static constexpr auto name = "ircChanName_"; };
 
-  struct Channel: Column<std::string> { static constexpr auto name = "channel_";
-    static constexpr auto options = ""; };
+  struct Channel: Column<std::string> { static constexpr auto name = "channel_"; };
 
-  struct IrcServerName: Column<std::string> { static constexpr auto name = "ircServerName_";
-    static constexpr auto options = ""; };
+  struct IrcServerName: Column<std::string> { static constexpr auto name = "ircServerName_"; };
 
-  struct Server: Column<std::string> { static constexpr auto name = "server_";
-    static constexpr auto options = ""; };
+  struct Server: Column<std::string> { static constexpr auto name = "server_"; };
 
-  struct Date: Column<time_point::rep> { static constexpr auto name = "date_";
-    static constexpr auto options = ""; };
+  struct Date: Column<time_point::rep> { static constexpr auto name = "date_"; };
 
-  struct Body: Column<std::string> { static constexpr auto name = "body_";
-    static constexpr auto options = ""; };
+  struct Body: Column<std::string> { static constexpr auto name = "body_"; };
 
-  struct Nick: Column<std::string> { static constexpr auto name = "nick_";
-    static constexpr auto options = ""; };
+  struct Nick: Column<std::string> { static constexpr auto name = "nick_"; };
 
-  struct Pass: Column<std::string> { static constexpr auto name = "pass_";
-    static constexpr auto options = ""; };
+  struct Pass: Column<std::string> { static constexpr auto name = "pass_"; };
 
   struct Ports: Column<std::string> { static constexpr auto name = "ports_";
-    static constexpr auto options = "";
     Ports(): Column<std::string>("6667") {} };
 
   struct TlsPorts: Column<std::string> { static constexpr auto name = "tlsPorts_";
-    static constexpr auto options = "";
     TlsPorts(): Column<std::string>("6697;6670") {} };
 
-  struct Username: Column<std::string> { static constexpr auto name = "username_";
-    static constexpr auto options = ""; };
+  struct Username: Column<std::string> { static constexpr auto name = "username_"; };
 
-  struct Realname: Column<std::string> { static constexpr auto name = "realname_";
-    static constexpr auto options = ""; };
+  struct Realname: Column<std::string> { static constexpr auto name = "realname_"; };
 
-  struct AfterConnectionCommand: Column<std::string> { static constexpr auto name = "afterConnectionCommand_";
-    static constexpr auto options = ""; };
+  struct AfterConnectionCommand: Column<std::string> { static constexpr auto name = "afterConnectionCommand_"; };
 
-  struct TrustedFingerprint: Column<std::string> { static constexpr auto name = "trustedFingerprint_";
-    static constexpr auto options = ""; };
+  struct TrustedFingerprint: Column<std::string> { static constexpr auto name = "trustedFingerprint_"; };
 
-  struct EncodingOut: Column<std::string> { static constexpr auto name = "encodingOut_";
-    static constexpr auto options = ""; };
+  struct EncodingOut: Column<std::string> { static constexpr auto name = "encodingOut_"; };
 
-  struct EncodingIn: Column<std::string> { static constexpr auto name = "encodingIn_";
-    static constexpr auto options = ""; };
+  struct EncodingIn: Column<std::string> { static constexpr auto name = "encodingIn_"; };
 
   struct MaxHistoryLength: Column<int> { static constexpr auto name = "maxHistoryLength_";
-    static constexpr auto options = "";
     MaxHistoryLength(): Column<int>(20) {} };
 
   struct RecordHistory: Column<bool> { static constexpr auto name = "recordHistory_";
-    static constexpr auto options = "";
     RecordHistory(): Column<bool>(true) {}};
 
-  struct RecordHistoryOptional: Column<OptionalBool> { static constexpr auto name = "recordHistory_";
-    static constexpr auto options = ""; };
+  struct RecordHistoryOptional: Column<OptionalBool> { static constexpr auto name = "recordHistory_"; };
 
   struct VerifyCert: Column<bool> { static constexpr auto name = "verifyCert_";
-    static constexpr auto options = "";
     VerifyCert(): Column<bool>(true) {} };
 
   struct Persistent: Column<bool> { static constexpr auto name = "persistent_";
-    static constexpr auto options = "";
     Persistent(): Column<bool>(false) {} };
 
   using MucLogLineTable = Table<Id, Uuid, Owner, IrcChanName, IrcServerName, Date, Body, Nick>;

src/database/table.hpp

@@ -28,6 +28,17 @@ void add_column_to_table(sqlite3* db, const std::string& table_name)
     }
 }
 
+
+template <typename ColumnType, decltype(ColumnType::options) = nullptr>
+void append_option(std::string& s)
+{
+  s += " "s + ColumnType::options;
+}
+
+template <typename>
+void append_option(...)
+{ }
+
 template <typename... T>
 class Table
 {
@@ -110,14 +121,13 @@ class Table
     str += ColumnType::name;
     str += " ";
     str += TypeToSQLType<RealType>::type;
-    str += " "s + ColumnType::options;
+    append_option<ColumnType>(str);
     if (N != sizeof...(T) - 1)
       str += ",";
     str += "\n";
 
     add_column_create<N+1>(str);
   }
-
   template <std::size_t N=0>
   typename std::enable_if<N == sizeof...(T), void>::type
   add_column_create(std::string&)