Argument Parsing

- On task modification, all attributes are canonicalized.

src/commands/Command.cpp

@@ -299,7 +299,8 @@ void Command::modify_task (Task& task, Arguments& arguments)
       std::string name;
       std::string value;
       Arguments::extract_attr (arg->_first, name, value);
-
+      if (Arguments::is_attribute (name, name))
+      {
         // TODO All 'value's must be eval'd first.
 
         // Dependencies must be resolved to UUIDs.
@@ -325,6 +326,9 @@ void Command::modify_task (Task& task, Arguments& arguments)
         else
           task.set (name, value);
       }
+      else
+        throw format (STRING_CMD_ADD_BAD_ATTRIBUTE, name);
+    }
 
     // Tags need special handling because they are essentially a vector stored
     // in a single string, therefore Task::{add,remove}Tag must be called as

src/en-US.h

@@ -173,6 +173,7 @@
 #define STRING_CMD_URGENCY_RESULT    "task {1} urgency {2}"
 #define STRING_CMD_ADD_USAGE         "Adds a new task."
 #define STRING_CMD_ADD_FEEDBACK      "Created task {1}."
+#define STRING_CMD_ADD_BAD_ATTRIBUTE "Unrecognized attribute '{1}'."
 #define STRING_CMD_MOD_UNEXPECTED    "Unexpected argument '{1}' found while modifying a task."
 #define STRING_CMD_LOG_USAGE         "Adds a new task that is already completed."
 #define STRING_CMD_IDS_USAGE_RANGE   "Shows only the IDs of matching tasks, in the form of a range."