Implement rmdir method for HNS buckets

[Mahalaxmibejugam]

rmdir method provides an implementation for deletion of empty directories for Hierarchical Namespace (HNS) enabled buckets.

• HNS-Aware Deletion: For HNS-enabled buckets, it uses the delete_folder API to perform an atomic deletion of the specified empty folder.
• Fallback Mechanism: If a bucket is not HNS-enabled or if the path refers to the bucket itself (with no folder specified), it reverts to the GCSFileSystem _rmdir implementation.
• Error Handling: It translates GCS-specific API exceptions into standard Python errors for fsspec compatibility
  1. NotFound is raised as FileNotFoundError. NotFound would be thrown by the API if the path is a file or if it doesn't exist.
  2. FailedPrecondition (for non-empty directories) is raised as OSError.
• Cache Invalidation: On successful deletion, it invalidates the cache for the deleted path and its parent to ensure the filesystem view remains consistent.
• Testing:Tests are added to validate the new rmdir logic, covering successful deletions on HNS buckets, correct error handling for non-empty or non-existent directories, and ensuring the method properly falls back to the standard behavior for non-HNS buckets

[martindurant]

Question: since HNS buckets have a true folder structure, it should be possible to ammend the directory listings cache rather than simply invalidate it when deleting, no? That could avoid unnecessary listings later on.

[ankitaluthra1]

/gcbrun

[Mahalaxmibejugam]

Question: since HNS buckets have a true folder structure, it should be possible to ammend the directory listings cache rather than simply invalidate it when deleting, no? That could avoid unnecessary listings later on.

@martindurant Invalidating the cache for a specific path was also invalidating the cache for all parent directories in the hierarchy. I have updated the logic to remove the cache entry only for the deleted directory and to update its immediate parent to remove the deleted directory's entry.

[ankitaluthra1]

/gcbrun

[ankitaluthra1]

/gcbrun

[ankitaluthra1]

/gcbrun

[Mahalaxmibejugam]

Question: since HNS buckets have a true folder structure, it should be possible to ammend the directory listings cache rather than simply invalidate it when deleting, no? That could avoid unnecessary listings later on.

@martindurant Invalidating the cache for a specific path was also invalidating the cache for all parent directories in the hierarchy. I have updated the logic to remove the cache entry only for the deleted directory and to update its immediate parent to remove the deleted directory's entry.

@martindurant Can you please review the latest changes following the cache update logic?

[martindurant]

This ought to be correct, but if some some reason the entry is duplicated in the parent, you would end up removing the wrong thing. I think a comprehension would be clearer:

Suggested change

	for i, entry in enumerate(self.dircache[parent]):
	if entry.get("name") == path:
	self.dircache[parent].pop(i)
	break
	self.dircache[parent] = [ent for ent in self.dircache[parent] if ent["name"] != path]

[Mahalaxmibejugam]

Thanks for suggestion, Initially I planned something similar to your suggestion but wanted to skip iterating over entire list if we have already removed the path from parent cache to optimize the code(might not give much performance difference though).

you would end up removing the wrong thing

Just to make sure I understand this correctly, were you referring that we will not be removing duplicate entry if it exists?