Don't register berkelydb as a store if it is not available on the system

[aucampia]

Currently we are always registering BerkelyDB regardless of whether it is available or not:

rdflib/rdflib/plugin.py

Lines 202 to 207 in cdaee27

	register(
	"BerkeleyDB",
	Store,
	"rdflib.plugins.stores.berkeleydb",
	"BerkeleyDB",
	)

This causes problems if we want to operate on all stores, for example to test some functionality, as a special exception is needed for BerkeleyDB:

rdflib/test/test_graph/test_graph.py

Lines 68 to 84 in 13ec1df

	def get_store_names() -> Set[Optional[str]]:
	names: Set[Optional[str]] = {*get_unique_plugin_names(plugin.Store)}
	names.difference_update({
	"default",
	"Memory",
	"Auditable",
	"Concurrent",
	"SPARQLStore",
	"SPARQLUpdateStore",
	"SimpleMemory",
	})
	names.add(None)
	if not has_bsddb:
	names.remove("BerkeleyDB")
	logging.debug("names = %s", names)
	return names

I think it would be best to only register the plugin if the store is available.

[eden-logistics]

Gonna try working on this, would adding some kind of availability check in the register method work?

[eden-logistics]

Also, I'm assuming the method should check if all plugins are available. Should I do that or just have a specific check for berkelydb?

[aucampia]

Gonna try working on this, would adding some kind of availability check in the register method work?

Also, I'm assuming the method should check if all plugins are available. Should I do that or just have a specific check for berkelydb?

Hi @Jtmcflea I think first and most critical is to just not register plugins we know won't work, sadly there is no generic check we can do for all plugins, we know berkeleydb won't work unless we can import berkeleydb - but berkelydb is really an exception here, not the rule. Most (all?) other stores will work fine with stock python. For other plugins like https://github.com/RDFLib/rdflib-sqlalchemy there may be similar considerations, but that is not something to worry about in this repo.

So I would suggest just do it for berkeleydb.

[eden-logistics]

Ok, I've moved the berkeleydb register to the top of the list and added if rdflib.plugins.stores.berkeleydb.has_bsddb: before it to check if the system has berkeleydb. I've also removed the exception in test_graph.py, which passed, and I'm currently running the validate action in github.

Any more tests or formatting things I might need to do? Sorry to ask, but I'm new at open source contribution in general.