Fix _cat_file / _cat_ranges not discoverable on WholeFileCacheFileSystem class#2010
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martindurant merged 2 commits intofsspec:masterfrom Apr 14, 2026
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Move _cat_file and _cat_ranges from SimpleCacheFileSystem to WholeFileCacheFileSystem so that these methods are discoverable via type(fs) and not only via instance attribute lookup. Also add a guard in CachingFileSystem.__getattribute__ so that whitelisted methods not defined on the current subclass fall through to the wrapped filesystem delegation instead of returning a broken lambda. Closes fsspec#2009
hadim
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_cat_file and _cat_ranges missing on WholeFileCacheFileSystem class_cat_file / _cat_ranges not discoverable on WholeFileCacheFileSystem class
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Fixes #2009
Problem
hasattr(type(fs), '_cat_file')returnsFalseforWholeFileCacheFileSystem, even thoughhasattr(fs, '_cat_file')returnsTrue. This is becauseCachingFileSystem.__getattribute__intercepts attribute access at the instance level, but the method is never defined on the class itself.Libraries like
universal_pathlibandzarrinspect capabilities viatype(fs)rather than the instance, which leads toAttributeError.Fix
Two changes:
Move
_cat_fileand_cat_rangesfromSimpleCacheFileSystemup toWholeFileCacheFileSystem. Both classes use the same whole-file caching logic (check cache, download if missing, read locally).SimpleCacheFileSysteminherits them unchanged.Guard the whitelist in
__getattribute__: the whitelist is shared across the hierarchy, but some entries only exist on certain subclasses. When a whitelisted method is not ontype(self), we now fall through to the wrapped filesystem delegation instead of returning a lambda that would raiseAttributeError.Note to maintainers
If this instance-only delegation is intentional by design, or if you'd prefer a different approach, happy to hear your guidance. We can adjust or close this accordingly.