interfaces: introduce and use a protocol class for the `base85` module See f2832de2a46c for details when this was done for the `bdiff` module. It looks like PEP-688 removed the special casing of `bytes` being a standin for any type of `ByteString`, and defines a `typing.Buffer` class (with a backport in `typing_extensions` for Python prior to 3.12). There's been a lot of churn in this area with pytype, but recent versions of pytype and PyCharm recognize this, and e.g. have `mercurial.node.hex()` defined as: from typing_extensions import Buffer def hex(data: Buffer, sep: str | bytes = ..., bytes_per_sep: int = ...) -> bytes This covers `bytes`, `bytearray`, and `memoryview` by default. Both of the C functions here use `y#` to parse the arguments, which means the arg is a byte-like object[2], so the args would appear to be better typed as `Buffer`. However, pytype has a bug that prevents using this from `typing_extensions`[3], and mypy complained `Unsupported left operand type for + ("memoryview")` in the pure module on line 37 (meaning it's only a subset of `Buffer`). So hold off on changing any of that for now. [1] https://peps.python.org/pep-0688/#no-special-meaning-for-bytes [2] https://docs.python.org/3/glossary.html#term-bytes-like-object [3] https://github.com/google/pytype/issues/1772

base85: avoid a spurious use-before-initialized warning in `pure` module The error wasn't possible because the only way for `acc` to not be initialized was if `len(text) == 0`. But then `0 % 5 == 0`, so no attempt at padding was done. It's a simple enough fix to not have PyCharm flag this though. The value needs to be reset on each loop iteration, so it's a line copy, not a line move.

typing: add type annotations to `mercurial/mdiff.py` We'll leave converting `diffopts` to `attrs` as another project.

mdiff: convert a few block definitions from lists to tuples These were flagged by adding type hints. Some places were using a tuple of 4 ints to define a block, and others were using a list of 4. A tuple is better for typing, because we can define the length and the type of each entry. One of the places had to redefine the tuple, since writing to a tuple at an index isn't supported. This change spills out into the tests, and archeology says it was added to the repo in this state. There was no reason given for the divergence, and I suspect it wasn't intentional. It looks like `splitblock()` is completely unused in the codebase.

interfaces: add the optional `bdiff.xdiffblocks()` method PyCharm flagged where this was called on the protocol class in `mdiff.py` in the previous commit, but pytype completely missed it. PyCharm is correct here, but I'm committing this separately to highlight this potential problem- some of the implementations don't implement _all_ of the methods the others do, and there's not a great way to indicate on a protocol class that a method or attribute is optional- that's kinda the opposite of what static typing is about. Making the method an `Optional[Callable]` attribute works here, and keeps both PyCharm and pytype happy, and the generated `mdiff.pyi` and `modules.pyi` look reasonable. We might be getting a little lucky, because the method isn't invoked directly- it is returned from another method that selects which block function to use. Except since it is declared on the protocol class, every module needs this attribute (in theory, but in practice this doesn't seem to be checked), so the check for it on the module has to change from `hasattr()` to `getattr(..., None)`. We defer defining the optional attrs to the type checking phase as an extra precaution- that way it isn't an attr with a `None` value at runtime if someone is still using `hasattr()`. As to why pytype missed this, I have no clue. The generated `mdiff.pyi` even has the global variable typed as `bdiff: intmod.BDiff`, so uses of it really should comply with what is on the class, protocol class or not.

interfaces: introduce and use a protocol class for the `bdiff` module This is allowed by PEP 544[1], and we basically follow the example there. The class here is copied from `mercurial.pure.bdiff`, and the implementation removed. There are several modules that have a few different implementations, and the implementation chosen is controlled by `HGMODULEPOLICY`. The module is loaded via `mercurial/policy.py`, and has been inferred by pytype as `Any` up to this point. Therefore it and PyCharm were blind to all functions on the module, and their signatures. Also, having multiple instances of the same module allows their signatures to get out of sync. Introducing a protocol class allows the loaded module that is stored in a variable to be given type info, which cascades through the various places it is used. This change alters 11 *.pyi files, for example. In theory, this would also allow us to ensure the various implementations of the same module are kept in alignment- simply import the module in a test module, attempt to pass it to a function that uses the corresponding protocol as an argument, and run pytype on it. In practice, this doesn't work (yet). PyCharm (erroneously) flags imported modules being passed where a protocol class is used[2]. Pytype has problems the other way- it fails to detect when a module that doesn't adhere to the protocol is passed to a protocol argument. The good news is that mypy properly detects this case. The bad news is that mypy spews a bunch of other errors when importing even simple modules, like the various `bdiff` modules. Therefore I'm punting on the tests for now because the type info around a loaded module in PyCharm is a clear win by itself. [1] https://peps.python.org/pep-0544/#modules-as-implementations-of-protocols [2] https://youtrack.jetbrains.com/issue/PY-58679/Support-modules-implementing-protocols

mdiff: tweak calls into `bdiff.fixws` to match its type hints It turns out that protocol classes can be used for modules too, which is great because all of the dynamically loaded modules (and their attributes) are currently inferred as `Any`. See the next commit for details. A protocol class for the `bdiff` module detected this (trivial) mismatch, so correct it first. The various implementations of this method are typed as taking a `bool`. The `cext` implementation parses its arguments with `PyArg_ParseTuple(args, "Sb:fixws", &s, &allws)`, which wants an `int`. But experimenting in `hg debugshell` under py38, passing `True` or `False` to `cext.fixws()` also works. We can change the implementation to use "p" (which was introduced in py33) instead of "b", but that's beyond the scope of this.

util: minor copy editing of the documentation for `mmapread()`

util: make `mmapread()` work on Windows again 522b4d729e89 started referencing `mmap.MAP_PRIVATE`, but that's not available on Windows, so `hg version` worked, but `make local` did not. That commit also started calling the constructor with the fine-grained `flags` and `prot` args, but those aren't available on Windows either[1] (though the backing C code doesn't seem conditionalized to disallow usage of them). I assume the change away from from the `access` arg was to provide the same options, plus `MAP_POPULATE`. Looking at the source code[2], they're not quite the same- `ACCESS_READ` is equivalent to `flags = MAP_SHARED` and `prot = PROT_READ`. `MAP_PRIVATE` is only used with `ACCESS_COPY`, which allows read and write. Therefore, we can't quite get the same baseline flags on Windows, but this was the status quo ante and `MAP_POPULATE` is a Linux thing, so presumably it works. I realize that typically the OS differences are abstracted into the platform modules, but I'm leaving it here so that it is obvious what the differences are between the platforms. [1] https://docs.python.org/3/library/mmap.html#mmap.mmap [2] https://github.com/python/cpython/blob/5e0abb47886bc665eefdcc19fde985f803e49d4c/Modules/mmapmodule.c#L1539

typing: add type annotations to the dirstate classes The basic procedure here was to use `merge-pyi` to merge the `git/dirstate.pyi` file in (after renaming the interface class to match), cleaning up the import statement mess, and then repeating the procedure for `mercurial/dirstate.pyi`. Surprisingly, git's dirstate had more hints inferred in its *.pyi file. After that, it was a manual examination of each method in the interface, and how they were implemented in the core and git classes to verify what was inferred by pytype, and fill in the missing gaps. Since this involved jumping around between three different files, I applied the same type info to all three at the same time. Complex types I rolled up into type aliases in the interface module, and used that as needed. That way if it changes, there's one place to edit. There are some hints still missing, and some documentation that doesn't match the signatures. They should all be marked with TODOs. There are also a bunch of methods on the core class that aren't on the Protocol class that seem like maybe they should be (like `set_tracked()`). There are even more methods missing from the git class. But that's a project for another time.