Fix broken async reference file system _cat_file method (#1734)

Co-authored-by: Martin Durant <[email protected]>

Author: mpiannucci

fsspec/implementations/reference.py

@@ -806,7 +806,9 @@ async def _cat_file(self, path, start=None, end=None, **kwargs):
             return part_or_url[start:end]
         protocol, _ = split_protocol(part_or_url)
         try:
-            await self.fss[protocol]._cat_file(part_or_url, start=start, end=end)
+            return await self.fss[protocol]._cat_file(
+                part_or_url, start=start0, end=end0
+            )
         except Exception as e:
             raise ReferenceNotReachable(path, part_or_url) from e
 

fsspec/implementations/tests/test_reference.py

@@ -513,6 +513,35 @@ def test_cat_file_ranges(m):
     assert fs.cat_file("d", 1, -3) == other[4:10][1:-3]
 
 
+@pytest.mark.asyncio
+async def test_async_cat_file_ranges():
+    fsspec.get_filesystem_class("http").clear_instance_cache()
+    fss = fsspec.filesystem("https", asynchronous=True)
+    session = await fss.set_session()
+
+    fs = fsspec.filesystem(
+        "reference",
+        fo={
+            "version": 1,
+            "refs": {
+                "reference_time/0": [
+                    "https://noaa-nwm-retro-v2-0-pds.s3.amazonaws.com/full_physics/2017/201704010000.CHRTOUT_DOMAIN1.comp",
+                    39783,
+                    12,
+                ],
+            },
+        },
+        fs={"https": fss},
+        remote_protocol="https",
+        asynchronous=True,
+    )
+
+    assert (
+        await fs._cat_file("reference_time/0") == b"x^K0\xa9d\x04\x00\x03\x13\x01\x0f"
+    )
+    await session.close()
+
+
 @pytest.mark.parametrize(
     "fo",
     [