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Literal type of engine argument incompatible with custom backends

See original GitHub issue

What is your issue?

In the recent typing improvements the engine argument for open_dataset was changed from Str to a Literal of xarrays internal engines. This will cause problems for all third party backend plugins.

We have several possibilities:

I don’t know if there is a way to know installed backends at type checking time. Then we could add this support. (I doubt this is possible seeing how dynamic these imports are)
Is it possible for these plugins to tell type checkers that their engine is valid, i.e. change the type signature of xarrays function? Then we should add a how-to in the docu.
Else we should probably revert to using Str.

Any typing experts here that could help?

Issue Analytics

State:
Created a year ago
Comments:5 (3 by maintainers)

Top GitHub Comments

1reaction

headtr1ckcommented, May 24, 2022

Or we could just have a global variable like SUPPORTED_BACKENDS: List[str] = Literal['netcdf4', 'zarr'] which is appended to when a user registers a new backend?

If you know how that works statically, I don’t see a way to do that. You can only get dynamic content from static types and not the other way around.

0reactions

headtr1ckcommented, May 24, 2022

Ok, let’s keep this issue open for a bit in case someone still finds a solution. But we should go back to Str before releasing the next version.

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