fix: treat empty string as no filter in mempalace_search wing/room

[KunalG67]

Fixes #1084

What does this PR do?

Treats empty string as None (no filter) in _sanitize_optional_name.
Previously, mempalace_search rejected empty-string wing/room values
with "must be a non-empty string" even though the schema marks them optional.
This broke LLM agents that default to filling every declared parameter with "".

How to test

Call mempalace_search with wing: "" and room: "" - should return
results instead of an error. Quick unit check:

from mempalace.mcp_server import _sanitize_optional_name
assert _sanitize_optional_name("") is None
assert _sanitize_optional_name(None) is None
assert _sanitize_optional_name("main") == "main"

Checklist

• Tests pass (python -m pytest tests/ -v)
• No hardcoded paths
• Linter passes (ruff check .)

[sha2fiddy]

Hey @KunalG67, your one-liner handles the exact reproduction case from #1084.

Heads-up on one edge case: whitespace-only strings (" ", "\t", "\n") still raise ValueError because sanitize_name at mempalace/config.py:27 rejects any string where not value.strip(). Agents trip on this the same way they produce "" (trailing space, stray tab). I've seen it in practice.

Changing the guard to value is None or not value.strip() covers both.

I've got four regression tests for this sitting on a local branch (empty + whitespace on list_rooms, list_drawers, search). Want me to paste the diff so you can fold them in, or send as a follow-up after yours lands?

[KunalG67]

@sha2fiddy Thanks! Updated to not value.strip() to cover whitespace only strings too. Feel free to paste the test diff ,happy to fold them in

[sha2fiddy]

Thanks for jumping on the whitespace case.

The 4 tests below drop into tests/test_mcp_server.py right before test_wal_redacts_sensitive_fields. They reuse the _patch_mcp_server helper already in that file. I ran them locally against your e27967b head, all 4 pass.

    # ── #1084: empty/whitespace filters normalize to None ───────────────

    def test_search_accepts_empty_wing_as_no_filter(self, monkeypatch, config, kg):
        """Empty-string wing must be treated as 'no filter', not a validation error.

        LLM agents that eagerly fill every declared parameter pass ``""`` to
        mean "no filter". Regression guard for #1084.
        """
        _patch_mcp_server(monkeypatch, config, kg)
        from mempalace import mcp_server

        captured = {}

        def _fake_search(query, palace_path, wing, room, n_results, max_distance):
            captured["wing"] = wing
            captured["room"] = room
            return {"results": []}

        monkeypatch.setattr(mcp_server, "search_memories", _fake_search)

        result = mcp_server.tool_search(query="JWT", wing="")
        assert "error" not in result
        assert captured["wing"] is None

    def test_search_accepts_whitespace_wing_as_no_filter(self, monkeypatch, config, kg):
        """Whitespace-only wing collapses to None — same rationale as empty string."""
        _patch_mcp_server(monkeypatch, config, kg)
        from mempalace import mcp_server

        captured = {}

        def _fake_search(query, palace_path, wing, room, n_results, max_distance):
            captured["wing"] = wing
            captured["room"] = room
            return {"results": []}

        monkeypatch.setattr(mcp_server, "search_memories", _fake_search)

        result = mcp_server.tool_search(query="JWT", wing="   ", room="\t")
        assert "error" not in result
        assert captured["wing"] is None
        assert captured["room"] is None

    def test_list_drawers_accepts_empty_room_as_no_filter(
        self, monkeypatch, config, palace_path, seeded_collection, kg
    ):
        """Empty-string room on list_drawers must not raise — regression for #1084."""
        _patch_mcp_server(monkeypatch, config, kg)
        from mempalace.mcp_server import tool_list_drawers

        result = tool_list_drawers(wing="", room="")
        assert "error" not in result
        assert "drawers" in result

    def test_list_rooms_accepts_empty_wing_as_no_filter(
        self, monkeypatch, config, palace_path, seeded_collection, kg
    ):
        """Empty-string wing on list_rooms must not raise — regression for #1084."""
        _patch_mcp_server(monkeypatch, config, kg)
        from mempalace.mcp_server import tool_list_rooms

        result = tool_list_rooms(wing="")
        assert "error" not in result
        assert result["wing"] == "all"

Rename or trim whatever doesn't fit your style.