Limit generated filename prefixes

src/py/kaleido/_utils/path_tools.py

@@ -14,10 +14,13 @@
 
 _logger = logistro.getLogger(__name__)
 
+_MAX_GENERATED_FILENAME_PREFIX_LENGTH = 80
+
 
 def _next_filename(path: Path | str, prefix: str, ext: str) -> str:
     """Figure out proper suffix for generated file name."""
     path = path if isinstance(path, Path) else Path(path)
+    prefix = prefix[:_MAX_GENERATED_FILENAME_PREFIX_LENGTH]
     default = 1 if (path / f"{prefix}.{ext}").exists() else 0
     re_number = re.compile(
         r"^" + re.escape(prefix) + r"\-(\d+)\." + re.escape(ext) + r"$",
@@ -60,7 +63,7 @@ def determine_path(
         prefix = re.sub(r"[ \-]", "_", prefix)
         prefix = re.sub(r"[^a-zA-Z0-9_]", "", prefix)
         prefix = prefix or "fig"
-        prefix = prefix[:80]  # in case of long titles
+        prefix = prefix[:_MAX_GENERATED_FILENAME_PREFIX_LENGTH]
         _logger.debug(f"Found: {prefix}")
         name = _next_filename(directory, prefix, ext)
         full_path = directory / name

src/py/tests/test_path_tools.py

@@ -69,6 +69,15 @@ def test_next_filename_only_numbered_files(tmp_path):
     assert result == "test-11.png"  # Should be max + 1
 
 
+def test_next_filename_caps_long_prefix_before_filesystem_lookup(tmp_path):
+    """Test _next_filename avoids probing overlong generated filenames."""
+    prefix = "a" * 500
+
+    result = path_tools._next_filename(tmp_path, prefix, "png")  # noqa: SLF001
+
+    assert result == f"{'a' * 80}.png"
+
+
 # Fixtures for determine_path tests - testing various title scenarios
 @pytest.fixture(
     params=[
@@ -137,6 +146,16 @@ def test_determine_path_directory_with_suffix(tmp_path, fig_fixture):
     assert result.name == f"{expected_prefix}.ext"
 
 
+def test_determine_path_caps_long_title_prefix(tmp_path):
+    """Test determine_path keeps generated filenames within path length limits."""
+    fig_dict = {"layout": {"title": {"text": "a" * 500}}}
+
+    result = path_tools.determine_path(tmp_path, fig_dict, "png")
+
+    assert result.parent == tmp_path
+    assert result.name == f"{'a' * 80}.png"
+
+
 def test_determine_path_file_with_suffix(tmp_path, fig_fixture):
     """Test determine_path with file path having suffix."""
     fig_dict, _expected_prefix = fig_fixture