Fix lazy reference handling for .parquet/.parq files

fsspec/implementations/reference.py

@@ -22,7 +22,7 @@
 from fsspec.callbacks import DEFAULT_CALLBACK
 from fsspec.core import filesystem, open, split_protocol
 from fsspec.implementations.asyn_wrapper import AsyncFileSystemWrapper
-from fsspec.utils import isfilelike, merge_offset_ranges, other_paths
+from fsspec.utils import get_file_extension, isfilelike, merge_offset_ranges, other_paths
 
 logger = logging.getLogger("fsspec.reference")
 
@@ -698,20 +698,20 @@ def __init__(
                 **(ref_storage_args or target_options or {}), protocol=target_protocol
             )
             ref_fs, fo2 = fsspec.core.url_to_fs(fo, **dic)
-            if ref_fs.isfile(fo2):
-                # text JSON
-                with fsspec.open(fo, "rb", **dic) as f:
-                    logger.info("Read reference from URL %s", fo)
-                    text = json.load(f)
-                self._process_references(text, template_overrides)
-            else:
+            if get_file_extension(fo2) in {"parq", "parquet"}:
                 # Lazy parquet refs
                 logger.info("Open lazy reference dict from URL %s", fo)
                 self.references = LazyReferenceMapper(
                     fo2,
                     fs=ref_fs,
                     cache_size=cache_size,
                 )
+            else:
+                # text JSON
+                with fsspec.open(fo, "rb", **dic) as f:
+                    logger.info("Read reference from URL %s", fo)
+                    text = json.load(f)
+                self._process_references(text, template_overrides)
         else:
             # dictionaries
             self._process_references(fo, template_overrides)

fsspec/tests/test_utils.py

@@ -9,6 +9,7 @@
 from fsspec.utils import (
     can_be_local,
     common_prefix,
+    get_file_extension,
     get_protocol,
     infer_storage_options,
     merge_offset_ranges,
@@ -337,6 +338,21 @@ def test_get_protocol(par):
     url, outcome = par
     assert get_protocol(url) == outcome
 
+@pytest.mark.parametrize(
+    ["url", "expected"],
+    (
+        ("https://example.com/q.txt", "txt"),
+        ("https://example.com/foo.parquet", "parquet"),
+        ("https://example.com/foo.parq", "parq"),
+        ("file:///home/user/no_extension", ""),
+        ("/local/path/to/file.json", "json"),
+        ("relative/path/file.yaml", "yaml"),
+    )
+)
+def test_get_file_extension(url, expected):
+    actual = get_file_extension(url)
+
+    assert actual == expected
 
 @pytest.mark.parametrize(
     "par",

fsspec/utils.py

@@ -437,6 +437,13 @@ def get_protocol(url: str) -> str:
         return parts[0]
     return "file"
 
+def get_file_extension(url: str) -> str:
+    url = stringify_path(url)
+    ext_parts = url.rsplit(".", 1) 
+    if len(ext_parts) > 1:
+        return ext_parts[-1]
+    return ""
+
 
 def can_be_local(path: str) -> bool:
     """Can the given URL be used with open_local?"""