Feat: Expose enum types as actual enums in py-rattler

[iamthebot]

Feat: Expose enum types as actual enums in py-rattler

[iamthebot]

Yeah, I can put up a PR Friday.

Update: Ended up a little busy today (4/26) so didn't get to this but will add it next week.

[baszalmstra]

Do you have an example and how you would change it?

[iamthebot]

For example, the current PathType class in rattler (eg; here) has getters for hardlink, softlink, etc. that just return True if the PathType is of that value. In other words, to get the path type you have to do a bunch of if/else until you hit a possible value that returns True. That's not really idiomatic and a major hassle if you have a lot of values. It also means downstream code needs to worry about any new enum values not being handled.

So for example, to determine the type of a path in Python I have to do something like:

(currently)

...
if path_type.directory:
  return "directory"
elif path_type.softlink:
  return "softlink"
elif path_type.hardlink:
  return "hardlink"

In the rust code in rattler-conda-types however (eg; here this is an enum. That is, the values are mutually exclusive. This means it would be also safe to expose these types as python enums.

If we did that, now it would be easy in python to:

1. Get all possible valid values for the enum
2. Convert from a string to the enum type easily
3. Convert from the enum type to a string
4. Check equality across enums of the same type

For example:

>>> print(path_type.value)
PathType.hardlink

>>> PathType["hardlink"] == PathType.hardlink
`True`

>>> assert path_type == PathType.symlink, "some assertion error"

Doing some cursory research, PyO3 does not natively have a way to export rust enums as Python enums. But a few approaches are suggested in this SO post. Another approach I don't see listed there that might be cleaner (and backwards compatible with older versions of Python) is to expose an int member for these types and on the python side have a matching int based enum with those values. That's more memory efficient too.

[baszalmstra]

Thanks for the writeup! That makes total sense to me. Would you be able to whip up a Pr?