Merge pull request #1557 from braingram/fsspec_fileno

test for valid fileno before creating RealFile

CHANGES.rst

@@ -12,6 +12,7 @@ The ASDF Standard is at v1.6.0
 - Remove deprecated legacy extension API [#1464]
 - Drop Python 3.8 support [#1556]
 - Drop NumPy 1.20, 1.21 support [#1568]
+- Fix issue opening files that don't support ``fileno`` [#1557]
 
 2.15.0 (2023-03-28)
 -------------------

asdf/_tests/test_generic_io.py

@@ -803,6 +803,11 @@ def test_fsspec(tmp_path):
         r = gf.read(len(ref))
         assert r == ref, (r, ref)
 
+        gf.seek(0)
+        arr = gf.read_into_array(len(ref))
+        for ai, i in zip(arr, ref):
+            assert ai == i
+
 
 @pytest.mark.remote_data()
 def test_fsspec_http(httpserver):
@@ -823,6 +828,11 @@ def test_fsspec_http(httpserver):
         r = gf.read(len(ref))
         assert r == ref, (r, ref)
 
+        gf.seek(0)
+        arr = gf.read_into_array(len(ref))
+        for ai, i in zip(arr, ref):
+            assert ai == i
+
 
 @pytest.mark.skipif(
     sys.platform.startswith("win"),

asdf/generic_io.py

@@ -1173,11 +1173,16 @@ def get_file(init, mode="r", uri=None, close=False):
         if init.seekable():
             init2 = init.raw if hasattr(init, "raw") else init
 
-            result = (
-                MemoryIO(init2, mode, uri=uri)
-                if hasattr(init2, "getvalue")
-                else RealFile(init2, mode, uri=uri, close=close)
-            )
+            if hasattr(init2, "getvalue"):
+                result = MemoryIO(init2, mode, uri=uri)
+            else:
+                # can we call 'fileno'? if not, we can't memmap so don't
+                # make a RealFile
+                try:
+                    init2.fileno()
+                    result = RealFile(init2, mode, uri=uri, close=close)
+                except io.UnsupportedOperation:
+                    result = RandomAccessFile(init2, mode, uri=uri, close=close)
 
             result._secondary_fd = init
             return result