Conditional Registration of Custom Source

[christoph-blessing]

Is it currently possible to conditionally register custom sources or is that only supported for builtin sources? I would be very grateful if anyone could show me how to do it if it is possible. :)

[jose-elias-alvarez]

Yes, you can dynamically register any source (custom or built-in) by using null_ls.register, described here. You can use an autocommand, custom function, or whatever else you want and everything should work as expected.

[christoph-blessing]

Thanks for the answer. I am aware that I can register any source dynamically. What I meant to ask is whether there is an interface similar to what is available for builtin sources. Sorry, I should have been more precise when asking my original question.
I tried passing the condition argument to generator_factory but that doesn't seem to work. Is that not supported or am I doing it wrong?

[jose-elias-alvarez]

generator_factory (which is part of the public API) is meant to make spawning commands and capturing their output easier by handling (most) common cases. make_builtin (which is not part of the public API) is meant to allow modifying built-in sources and handle common registration cases. condition belongs to the latter, which is why passing condition into generator_factory didn't do anything.

You can see here that the condition logic is pretty trivial – the source should be wrapped with a function that either returns the source itself or nil depending on whether the source should be registered.

You can use make_builtin outside of null-ls, but that API isn't public and may change at any time. Also, at the moment, you cannot use condition when creating a built-in, only when modifying it via with (though #413 will change that).