Add a way to use currently defined reader macros with hy.read-many and hy.read

[Kodiologist]

Currently there is no (official) way to read code that uses reader macros defined by the active reader.

[scauligi]

This currently works:

(defreader foo 3)
(setv reader (hy.reader.HyReader))

;; import all readers from current module into reader
(hy.eval (hy.read f"(require {__name__} :readers *)" :reader reader))

(hy.read "#foo" :reader reader)

A slightly more direct solution is:

(hy.macros.enable-readers None reader "ALL")

since that's the only part of require we actually need.

Is enable-readers considered part of the public API?

[Kodiologist]

I'd say it isn't, currently. Originally Allie had intended it to be, the idea being that reader macros can be surprising, and so by calling enable-readers explicitly the user would be opting into reader macros. I argued that (defreader …) or (require foo :readers …) was enough of an opt-in. So in her final version of the PR, enable-readers no longer had to be called by the user, but it remained part of the implementation.

[scauligi]

I can make a PR to clean up and expose enable-readers for this use-case; the only caveat is that since (like many of the functions from hy/macros.py) it uses inspect.stack()[1] to get the module of the immediate caller, which can lead to potential confusion on the off chance a user is wrapping/calling this indirectly from a utility submodule or something. I don't have a solution to that aside from making sure it's documented, so hopefully that will suffice.

[Kodiologist]

Maybe hy.read could have a special parameter that would enable loading all reader macros from the current module first. Or it could be a parameter of the HyReader constructor.

…it uses inspect.stack()[1] to get the module of the immediate caller, which can lead to potential confusion on the off chance a user is wrapping/calling this indirectly from a utility submodule or something. I don't have a solution to that aside from making sure it's documented, so hopefully that will suffice.

Yes, I think just documenting it should suffice.