The 'key' field is mandatory and it must be of type integer.
Its purpose is to provide a primary key that is independent from the default GRASS primary key (normally in integer field 'cat').
Since input maps will often not have an extra integer field with unique values, some users might struggle with this requirement.
An easy convenience fix would be the following:
If 'key' field exist: check it for validity (already implemented).
If 'key' field does not exist: Add a new INT field with that name, then fill it with a 1..n pkey sequence.
The 'key' field is mandatory and it must be of type integer. Its purpose is to provide a primary key that is independent from the default GRASS primary key (normally in integer field 'cat').
Since input maps will often not have an extra integer field with unique values, some users might struggle with this requirement.
An easy convenience fix would be the following: