Allow production lists to refer to tokens from other production groups.

[silene]

Feature or Bugfix

• Feature

Purpose

Outside production lists, syntax `foo:bar` already makes it possible to refer to the production bar of group foo. This commit offers the same feature inside production lists. Similarly to the reference syntax, prefixing with a tilde prevents the group from being displayed.

This commit also makes it possible to use `:bar` to refer to production bar from a production list without a group name. This is especially useful when one has a main (unnamed) grammar and one or several named extensions that need to refer to it.

[tk0miya]

Looks good. Could you add testcases for this new syntax?

[silene]

I am a bit confused with the testing framework. I suppose I can add some testcases to tests/roots/test-productionlist/. But are there some reference files somewhere else that are used to assert that the output is correct? Or is it just a matter of getting the files to compile without errors/warnings?

[tk0miya]

This is a testcase that corresponds with tests/roots/test-productionlist/. It builds the document and inspect the result.
https://github.com/sphinx-doc/sphinx/blob/3.x/tests/test_domain_std.py#L352-L405

It's okay to modify them or to add new pair of project under tests/roots/ and testcase in test_domain_std.py.

[silene]

Thanks for the help. It seemed a bit too frail and tedious to parse the HTML output. (Contrarily to the other tests for productionlist, it is the productions themselves that had to be parsed, and they have no structure.) So, I instead decided to check the doctree, as many other tests do.

[tk0miya]

Thank you for your work. LGTM!

[tk0miya]

Note: I was wrongly labeled this as "4.0.0". But it's unexpected.