Fix Vector info bug #359

[linakrisztian]

#359: By changing v.info -c to v.db.connect -c, GRASS does not return an error for vector maps with missing table. Instead this message is printed: "Map <test_random_vect> is not connected to a database". Thus the endpoint does not return an error anymore.

[griembauer]

Thanks, looks good and tested successfully locally!

[metzm]

Do you really want to print types/names of table columns for the specified layer (default is layer 1) or rather print all map connection parameters for all layers, would be empty if there are no connections?

Suggested change

	"flags": "c"}
	"flags": "g"}

[linakrisztian]

@anikaweinmann or @mmacata : The old case (v.info -c) also printed only type/names of the specified layer (default layer 1). Should we change it as @metzm suggested?

[anikaweinmann]

I think v.db.connect -c is the one which is like it is now. So I would prefer this. The style of g is anonther one than we have a breaking change, or not?

[anikaweinmann]

Check with v.db.connect -g if there are more than 1 layer/tables or no layers (count number of rows). If there is only one layer the output should be v.info -c as before, by multiple layer/tables v.db.connect -g should be inside the results. By no layer/table nothing has to be added to the results.

Open question: how to write this in the api docs.

[metzm]

A GRASS vector can have no database connection at all or one or several database connections, one possible connection for each layer. The common case is that a vector has one database connection, the corresponding layer is layer 1. For other cases v.info -c or v.db.connect -c does not make sense because no columns would be reported or only columns for layer 1, ignoring attribute columns for other layers.
The class EphemeralVectorInfo()reports general information about a vector. Therefore I would argue that this is the wrong place for column names and types of a specific layer. Instead, any database connections as reported by v.db.connect -g() would be useful information in this place. After that, a user might want to know column names and types of a specific vector layer, see also https://github.com/OSGeo/grass/blob/main/python/grass/script/vector.py#L101.

Maybe introduce a new endpoint where the layer of a vector can be specified?

[metzm]

Instead of a new endpoint for a vector layer, the syntax also recognized by TGIS could be used: <name>:<layer>@<mapset>. If a layer is given, v.db.connect -c layer=<layer> map=<name> could be used, otherwise v.db.connect -g map=<name>.