Allow typing.Self as a hint-type.

[lojack5]

Initial implementation for allowing typing.Self as a hint-type for Structured classes.

Note there are no safeguards to prevent hitting the recursion limit. I'm thinking of just allowing it, with the warning in the readme.

Should be backwards-compatible with < Python 3.11 via typing-extensions.

[lojack5]

@davidcurie Implementing the typing.Self typehint as a Serializable type wasn't too bad (had to troubleshoot some CI stuff due to the last 3.12 tests running when 3.12 was still in RC stage).

You can check out this branch and let me know if it suits your needs (as mentioned in #2 ), I'm guessing you can at least get unpacking to work with this. It's ready to go into main, just wanted to run it by you in case there was anything you wanted added/changed in this aspect.

[davidcurie]

In my use case, I'm using typing.Self as a conditional unpacking based on LookbackDecider.

from typing import Self, Union
from structured import Structured, LookbackDecider, uint16  # and other types

dtype_map = {
    0: Self,
    1: uint16,
    ⋮
}

class MyStruct(Structured):
    key: unicode[uint32]
    dtype: uint32
    start: uint64
    stop: uint64
    value: Annotated[Union[dtype_map.values], LookbackDecider(attrgetter("dtype"), dtype_map)]

The sanitation check taking place in serializers/unions.py prevents me from using this structure.

Traceback:
  File "path/to/my/example_test-self.py", line 39, in MyStruct
    value: Annotated[Union[dtype_map.values], LookbackDecider(attrgetter("dtype"), dtype_map)]
                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/anaconda3/envs/testing-env/lib/python3.11/site-packages/structured/serializers/unions.py", line 120, in __init__
    super().__init__(result_map, default)
  File "/opt/anaconda3/envs/witec-testing/lib/python3.11/site-packages/structured/serializers/unions.py", line 47, in __init__
    self.result_map = {
                      ^
  File "/opt/anaconda3/envs/testing-env/lib/python3.11/site-packages/structured/serializers/unions.py", line 48, in <dictcomp>
    key: self.validate_serializer(serializer)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/anaconda3/envs/witec-testing/lib/python3.11/site-packages/structured/serializers/unions.py", line 57, in validate_serializer
    raise TypeError(f'Union results must be serializable types, got {hint!r}.')
TypeError: Union results must be serializable types, got typing.Self.

Am I understanding the intended implementation incorrectly?

[lojack5]

Ah, thanks for the test. Nope that is supposed to work, but I forgot to dig into the method than handles transforms for all other types. Will push a fix for that in a bit.

[lojack5]

Might take a while longer than I thought. Some added tests revealed issues brought up due to the recursive possibilities. Thought I had it, everything was working except for array[Header[...], Self]. Now I gotta think carefully about recursion - probably brought on that the serializer on a Structured object is actually a class variable (and so shared between instances).

[lojack5]

Ok, took another pass at this, should be good to go for testing on your end. typing.Self should now be properly handled in all container-type hints (unions, arrays, etc).

[davidcurie]

I haven't explored all edge cases, but I can confirm that the error I described above no longer shows up. At the Structured level, this seems to work with how I would use it.

[lojack5]

Sounds good, if you run into any issues let me know.