Fix path tab completion erasing line when cursor is on / or -

metakernel/_metakernel.py

@@ -600,6 +600,13 @@ async def do_complete(self, code: str, cursor_pos: int) -> dict[str, Any]:
             "metadata": {},
         }
 
+        # When the cursor sits after a non-identifier character (e.g. `/`, `-`) the
+        # id_regex matches empty string, setting cursor_start to 0.  Path completions
+        # are already stripped of their prefix, so we only need to append them at the
+        # cursor position — not replace from the beginning of the line.
+        if not info["obj"] and info["path_matches"]:
+            content["cursor_start"] = content["cursor_end"]
+
         matches = info["path_matches"]
 
         if info["magic"]:

tests/test_metakernel.py

@@ -156,6 +156,30 @@ def test_ls_path_complete() -> None:
     assert comp["matches"] == ["ipython/"], comp
 
 
+@pytest.mark.skipif(
+    sys.platform == "win32", reason="path completion format differs on Windows"
+)
+def test_path_complete_trailing_slash() -> None:
+    """Cursor after '/' must not replace the whole line (issue #432)."""
+    kernel = get_kernel()
+    text = "%cd /"
+    comp = asyncio.run(kernel.do_complete(text, len(text)))
+    assert comp["cursor_start"] == comp["cursor_end"] == len(text), comp
+    assert len(comp["matches"]) > 0, "expected filesystem entries under /"
+
+
+@pytest.mark.skipif(
+    sys.platform == "win32", reason="path completion format differs on Windows"
+)
+def test_path_complete_trailing_dash() -> None:
+    """Cursor after '-' in a path must not replace the whole line (issue #432)."""
+    kernel = get_kernel()
+    text = "%ls /tmp/nonexistent-"
+    comp = asyncio.run(kernel.do_complete(text, len(text)))
+    # Even with no matches, cursor_start must not be 0 when there is a path prefix
+    assert comp["cursor_start"] != 0 or comp["matches"] == [], comp
+
+
 def test_history() -> None:
     kernel = get_kernel()
     asyncio.run(kernel.do_execute("!ls", False))