Draft: Add type hints #267

igorp-collabora · 2025-08-01T15:30:09Z

Work in progress.

Files type hints added to:

src/configobj/validate.py
src/configobj/__init__.py
Add py.typed marker

CI stages added to verify typing:

Mypy. Mypy has to be version 1.16 at it is the last version that can type check Python 3.8.

igorp-collabora · 2025-08-01T15:32:23Z

src/configobj/validate.py

            arg_match = self._matchfinder.match(arg_string)
            if arg_match is None:
                # Bad syntax
                raise VdtParamError('Bad syntax in check "%s".' % check)


I believe there is a real bug here:

src/configobj/validate.py:643: error: Missing positional argument "value" in call to "VdtParamError" [call-arg] raise VdtParamError('Bad syntax in check "%s".' % check) ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Found 1 error in 1 file (checked 1 source file)

VdtParamError takes 2 arguments to its initializer but only 1 is passed here. I haven't changed the code as it probably belongs to another PR.

Yeah, I agree - it would be great if you could submit a separate PR for this.

Hmmm... After some investigation I believe this was already fixed in the master branch but not release branch: dff3ca0

I am not entirely sure what is the relationship between those two branches.

igorp-collabora · 2025-08-01T15:35:38Z

The dict[..., ...] syntax was added in the Python 3.9 but from __future__ import annotations should prevent the code from evaluating on older Python versions. (older versions used typing.Dict[..., ...])

src/configobj/validate.py

jelmer · 2025-08-01T17:52:52Z

src/configobj/validate.py

    """An unknown check function was requested"""

-    def __init__(self, value):
+    def __init__(self, value: Any):


There is no value in adding "Any" annotations; can we be more specific here? Even just having a "Value" type alias might be useful for readability - and there are certain constraints on Values I think.

The value will be converted to a string anyway:

ValidateError.__init__(self, 'the check "%s" is unknown.' % (value,))

The object can be used here because any object can be converted to string: https://github.com/python/typeshed/blob/2888ec7011f5f2623fd3f3718d4668311932bb30/stdlib/builtins.pyi#L123

My plan is to add type hints with as minimal changes to the code as possible. Because of dynamic nature of existing code the use of Any is basically required. If you look at how serialization libraries are typed in standard library, all of them return Any when serialising or deserialising data: https://github.com/python/typeshed/blob/2888ec7011f5f2623fd3f3718d4668311932bb30/stdlib/json/__init__.pyi#L60

src/configobj/validate.py

igorp-collabora · 2025-08-04T16:25:31Z

I added very early __init__.py. This file is pretty large. I will refine them in the following days.

igorp-collabora · 2025-08-04T16:26:21Z

src/configobj/__init__.py

+def getObj(s) -> Any:
    global compiler
    if compiler is None:
        import compiler


I have no idea what this compiler module is. Nothing on PyPI matches it.

igorp-collabora · 2025-08-04T16:27:26Z

src/configobj/__init__.py

    pass


 class Builder(object):


I don't believe this class is actually used anywhere?:

$ rg '_builder' src/ src/configobj/__init__.py 197:_builder = Builder()

igorp-collabora · 2025-08-05T10:42:22Z

src/configobj/__init__.py

+    def _interpolate(self, key: str, value: Any) -> Any:
        try:
            # do we already have an interpolation engine?
            engine = self._interpolation_engine


I believe there might be a bug in this function. First the name = self.main.interpolation where interpolation is a bool. If interpolation then name will be assigned a string and .lower() will be called. However, if interpolation then name will remain a bool that does not have .lower() method.

I belive what prevents it is that __getitem__ checks for self.main.interpolation before calling _interpolate but if this check was omitted this function would definitely raise an error.

igorp-collabora · 2025-08-05T12:33:14Z

src/configobj/__init__.py

-    def _decode(self, infile, encoding):
+    def _decode(self, infile: str | bytes | list[bytes] | list[str] | tuple[str, ...], encoding: str | None) -> list[str]:
        """
        Decode infile to unicode. Using the specified encoding.


There is an issue with this function. It says that it will decode file to unicode (str) but if encoding is None it will happily return bytes. encoding can be None because self.encoding can also be None.

igorp-collabora · 2025-08-05T13:10:10Z

src/configobj/__init__.py

-        self.configspec = None
+        self.initial_comment: list[str] = []
+        self.final_comment: list[str] = []
+        self.configspec: ConfigObj | None = None


There are a lot of type checking errors because self.configspec can be None. The None is not being checked for.

igorp-collabora · 2025-08-05T13:21:08Z

I reduced number of type errors from over 300 to 44 but it is still pretty ugly. Here is the mypy output: https://gist.github.com/igorp-collabora/5eaa20e23b063d04f986d08d53d7c29a

jelmer · 2025-09-28T23:14:13Z

Hi @igorp-collabora , are you still working on this?

igorp-collabora · 2025-09-29T10:27:55Z

Hi @igorp-collabora , are you still working on this?

I ran in to some questions that I didn't have answers for:

What is the relationship between release and master branches. For example, dff3ca0 bug fix is in master but not release. Should PR target master or release?
What is this whole compiler and getObj thing that does not seems to be reachable? Can it be removed? (this will simplify type hint)

jelmer · 2025-09-30T22:20:17Z

Hi @igorp-collabora , are you still working on this?

I ran in to some questions that I didn't have answers for:

1. What is the relationship between `release` and `master` branches. For example, [dff3ca0](https://github.com/DiffSK/configobj/commit/dff3ca058d1d98f3078c17836435ca5af3a8c4a6) bug fix is in master but not release. Should PR target master or release?

Please target master. I'm working to simplify the branch situation.

2. What is this whole `compiler` and `getObj` thing that does not seems to be reachable? Can it be removed? (this will simplify type hint)

We can remove this. The compiler module used to be shipped with Python 2 (prior to 2.7?). Since we only support Python 3, we can drop it.

igorp-collabora · 2025-10-02T09:58:41Z

Looks like master branch has already removed the compiler module. I will see if I can rework this MR to target master.

igorp-collabora · 2025-10-17T15:13:15Z

I've changed the target of this PR to master branch. There is still some difference between release and master .

igorp-collabora commented Aug 1, 2025

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igorp-collabora mentioned this pull request Aug 1, 2025

mypy stub for ConfigObj #184

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jelmer requested changes Aug 1, 2025

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igorp-collabora force-pushed the type-checking branch from 0165c35 to d741891 Compare August 4, 2025 13:04

igorp-collabora commented Aug 4, 2025

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igorp-collabora commented Aug 5, 2025

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igorp-collabora force-pushed the type-checking branch from d398e2c to c165064 Compare August 5, 2025 12:15

igorp-collabora commented Aug 5, 2025

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igorp-collabora force-pushed the type-checking branch from c165064 to 8c1f63e Compare August 5, 2025 13:19

Draft: Add type hints to src/configobj/validate.py

1c90267

igorp-collabora force-pushed the type-checking branch from 8c1f63e to 1c90267 Compare October 17, 2025 15:02

igorp-collabora changed the base branch from release to master October 17, 2025 15:03

Draft: Add type hints #267

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Draft: Add type hints #267

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