fix(storage): unlink dir symlinks without deleting targets

[fxprunayre]

Summary

Nextcloud supports following symbolic links when localstorage.allowsymlinks is enabled. However, deleting a symbolic link to a directory recursively deleted the contents of the target directory before failing to remove the link itself.

This change detects when the path passed to local storage directory removal is a symbolic link and unlinks it directly, preserving the target directory and its contents.

Before

Given:

.
├── afolder
│   └── test.txt
├── alink -> afolder
└── welcome.txt

Created with:

mkdir afolder
touch afolder/test.txt
ln -s afolder alink

Deleting alink recursively removed afolder/test.txt and then reported an error:

{
  "method": "DELETE",
  "url": "/remote.php/dav/files/admin/alink",
  "message": "rmdir(/data/dev/nextcloud/data/admin/files/alink): Not a directory"
}

The resulting structure was:

.
├── afolder
└── welcome.txt

After

Deleting alink now removes only the symbolic link. The link target and its contents are preserved:

.
├── afolder
│   └── test.txt
└── welcome.txt

Implementation

• Resolve the local source path once.
• Clear cached filesystem metadata before checking the path type.
• Detect a top-level symbolic link before constructing the recursive directory iterator.
• Unlink symbolic links directly instead of traversing their targets.
• Preserve the existing recursive removal behavior for real directories.
• Simplify the control flow in Local::rmdir().

Added parameterized regression coverage in LocalTest.php for deletion through both storage entry points:

• Local::rmdir()
• Local::unlink()

The tests verify that:

• The symbolic link is removed.
• The target directory remains.
• Files inside the target remain.
• The target file contents are unchanged.
• Environments that cannot create symbolic links skip the test.

Todo

Quite new to the Nextcloud codebase, any pointer to a test related to symlink is welcomed.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

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[joshtrichards]

Makes sense. Sorry about taking so long to review!

I took the liberty of:

• moving the clearstatcache() before the is_link() call
• refactoring slightly for clarity
• adding unit tests

[joshtrichards]

/backport to stable35

[joshtrichards]

/backport to stable34

[joshtrichards]

/backport to stable34

[joshtrichards]

/backport to stable33

[joshtrichards]

/backport to stable32