Removed unused TiffImagePlugin IFD_LEGACY_API

[radarhere]

This value is not used anywhere.

Pillow/src/PIL/TiffImagePlugin.py

Line 72 in 6377321

IFD_LEGACY_API = True

[hugovk]

Searching the top 8k PyPI projects only shows use in Pillow and type checkers:

❯ python3 ~/github/misc/cpython/search_pypi_top.py -q . IFD_LEGACY_API
./pytype-2024.4.11.tar.gz: pytype-2024.4.11/pytype/typeshed/stubs/Pillow/PIL/TiffImagePlugin.pyi: IFD_LEGACY_API: bool
./pillow-10.3.0.tar.gz: pillow-10.3.0/src/PIL/TiffImagePlugin.py: IFD_LEGACY_API = True
./pillow-10.3.0.tar.gz: pillow-10.3.0/src/PIL/TiffImagePlugin.py: # undone -- switch this pointer when IFD_LEGACY_API == False
./pyre-check-0.9.22.tar.gz: pyre_check-0.9.22/typeshed/stubs/Pillow/PIL/TiffImagePlugin.pyi: IFD_LEGACY_API: bool
./types-Pillow-10.2.0.20240520.tar.gz: types-Pillow-10.2.0.20240520/PIL-stubs/TiffImagePlugin.pyi: IFD_LEGACY_API: bool

Time: 0:00:29.920569
Found 5 matching lines in 4 projects

Likewise with grep.app:

https://grep.app/search?q=IFD_LEGACY_API&case=true

And GitHub, where it's also in some AST symbol tables, but they look like dumps of specific versions:

https://github.com/search?q=IFD_LEGACY_API&ref=opensearch&type=code&p=1

Technically this is a breaking change, but I think we can make an exception to the deprecation period, and go straight to removal in a major version. Let's also document it in the release notes and removals.

[hugovk]

Let's move this under "Backwards Incompatible Changes"

[radarhere]

Done

[hugovk]

Are there still plans to switch this in the future?

[wiredfool]

There were something like 3 stages to the tiff IFD modernization, and I got through stage 1, years back now. Something like it is going to be required if we're going to do robust tiff tags, but it's not on my list anymore.

[radarhere]

I've restored the comment that it is 'undone' to 'switch this pointer'