Conflicts and overrides

Conflicts between arguments, be them options, positional arguments or commands, can arise for a variety of reasons:

• Two options have the same name (either long or short)
• Two arguments have the same destination key, but different types (e.g. one is Any and the other String)
• Two arguments have the same destination key, but incompatible actions (e.g. one does :store_arg and the other :append_arg)
• Two positional arguments have the same metavar (and are therefore indistinguishable in the usage and help screens and in error messages)
• An argument and a command, or two commands, have the same destination key.

When the general setting error_on_conflict is true, or any time the specific force_override table entry setting is false, any of the above conditions leads to an error.

On the other hand, setting error_on_conflict to false, or force_override to true, will try to force the resolution of most of the conflicts in favor of the newest added entry. The general rules are the following:

• In case of duplicate options, all conflicting forms of the older options are removed; if all forms of an option are removed, the option is deleted entirely
• In case of duplicate destination key and incompatible types or actions, the older argument is deleted
• In case of duplicate positional arguments metavars, the older argument is deleted
• A command can override an argument with the same destination key
• However, an argument can never override a command if they have the same destination key; neither can a command override another command when added with @add_arg_table (compatible commands are merged by import_settings though)