[muthukkumaranb]

Description

SimpleDirectoryReader passes Path/PurePosixPath objects directly to fs.open(). Most fsspec
filesystems accept these, but DirFileSystem._join() only handles str, list and dict, so it tries
to iterate the path and fails with TypeError: 'PurePosixPath' object is not iterable.

This PR converts the path to str at the three fs.open() call sites (read_file_content,
load_file, aload_file). Other filesystems are unaffected because they already accept plain strings.

Fixes #23663

New Package?

• Yes
• No

Version Bump?

• Yes
• No (llama-index-core is exempt)

Type of Change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• I added new unit tests to cover this change

Added a dir_fs fixture (a MemoryFileSystem wrapped in a DirFileSystem) and three tests covering
load_data, aload_data and read_file_content. All three failed before the fix with the TypeError
and pass after it.

uv run -- pytest tests/readers in llama-index-core: 34 passed.
ruff format --check and ruff check pass on the changed files.

Suggested Checklist:

• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that prove my fix is effective
• New and existing unit tests pass locally with my changes

AI disclosure: I used an AI assistant (Claude) to help locate the call sites and draft the
regression tests. I reproduced the bug myself, reviewed every line, and ran the tests listed above.