class PSFile:
     """
     Wrapper for bytesio object that treats either CR or LF as end of line.
+    This class is no longer used internally, but kept for backwards-compatibility.
     """

If we're no longer using it internally, do we need to keep it around in the API?

Can it be deprecated? Is there a replacement?

"PSFile is part of the public API, so we'd need to raise deprecation warnings for at least a year first before it can be removed in a major bump, which would be Pillow 11.0.0 in October 2024." - hugovk #6877 (comment)

I don't know how to add a deprecation warning though; I haven't done that before.

Yup.

To deprecate something:

• Raise a DeprecationWarning using https://pillow.readthedocs.io/en/stable/reference/internal_modules.html#PIL._deprecate.deprecate with when=11 (depends on Handling for deprecations to be removed in Pillow 11 #6905)

• Update tests so we're not getting lots of deprecation warnings, add add a new test that explicitly checks for a warning with with pytest.warns(DeprecationWarning).

• Document it at https://pillow.readthedocs.io/en/stable/deprecations.html and in release notes, ideally telling the user what they need to do if they're using it.

Searching the top 5k projects on PyPI shows no real use of PSFile:

$ python3 ~/github/misc/cpython/search_pypi_top.py . "\bPSFile\b" -q
./pyre-check-0.9.16.tar.gz: pyre-check-0.9.16/typeshed/stubs/Pillow/PIL/EpsImagePlugin.pyi: class PSFile:
./Pillow-9.3.0.tar.gz: Pillow-9.3.0/Tests/test_file_eps.py: t = EpsImagePlugin.PSFile(f)
./Pillow-9.3.0.tar.gz: Pillow-9.3.0/Tests/test_file_eps.py: t = EpsImagePlugin.PSFile(r)
./Pillow-9.3.0.tar.gz: Pillow-9.3.0/src/PIL/EpsImagePlugin.py: class PSFile:
./Pillow-9.3.0.tar.gz: Pillow-9.3.0/src/PIL/EpsImagePlugin.py: fp = PSFile(self.fp)
./pytype-2022.10.26.tar.gz: pytype-2022.10.26/pytype/typeshed/stubs/Pillow/PIL/EpsImagePlugin.pyi: class PSFile:
./types-Pillow-9.3.0.0.tar.gz: types-Pillow-9.3.0.0/PIL-stubs/EpsImagePlugin.pyi: class PSFile:

Time: 0:00:23.017025
Found 7 matching lines in 4 projects

And I didn't spot any relevant use in the 940 GitHub results.

But before we go ahead, @radarhere what are your thoughts?

I don't mind deprecating PSFile. If it isn't used, then removing it makes things simpler.

You've also made various other changes here, such as making use of memoryview, which isn't used anywhere else in Pillow at the moment. Could you explain them a bit?

This plugin reads lines byte-by-byte until it reaches the end of the line (or 255 bytes). PSFile does this by appending each byte to a list, joining the list, and decoding the bytes to a string.