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method resolution surprise on EarthAccessFile #610

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itcarroll opened this issue Jun 25, 2024 · 5 comments · Fixed by #620 · May be fixed by #828
Open

method resolution surprise on EarthAccessFile #610

itcarroll opened this issue Jun 25, 2024 · 5 comments · Fixed by #620 · May be fixed by #828
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type: bug Something isn't working

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@itcarroll
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itcarroll commented Jun 25, 2024

There's something funny going on with the wrapping of fsspec.spec.AbstractBufferedFile, where the method resolution isn't coming out as expected.

The following gives me an AssertionError

import earthaccess

auth = earthaccess.login()
results = earthaccess.search_data(short_name="VIIRSJ1_L2_OC", count=1)
files = earthaccess.open(results)
with files[0] as g:
    assert g.read is getattr(g.f, "read")

I don't know about the internals, but getattr(g, "read") and g.__getattribute__("read") both follow the MRO to the read method of fsspec.spec.AbstractBufferedFile. We don't want that! We want the read method, given by g.__getattr__("read") as fsspec.implementations.http.HTTPFile.read as resulting from getattr(g.f) in the class definition.

class EarthAccessFile(fsspec.spec.AbstractBufferedFile):
def __init__(self, f: fsspec.AbstractFileSystem, granule: DataGranule) -> None:
self.f = f
self.granule = granule
def __getattr__(self, method: str) -> Any:
return getattr(self.f, method)

Is it possible that __getattr__ should be __getattribute__?

Sorry for the multiple edits; confused myself with two fs

@itcarroll itcarroll changed the title method resolution surprise on EarthAccessGranule method resolution surprise on EarthAccessFile Jun 25, 2024
@itcarroll
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No, don't use __getattribute__ b/c it leads to infinite recursion. New idea: this is not a class that should be subclassing at all.

@itcarroll
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When #620 removed the inherited fsspec.spec.AbstractBufferedFile class from earthaccess.EarthAccessFile, it broke the ability of xarray.backends.list_engines()["h5netcdf"].guess_can_open to recognize these pointers. It comes back to MRO, and the fact that EarthAccessFile is no longer an instance of io.IOBase.

@itcarroll itcarroll reopened this Sep 24, 2024
@itcarroll
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It would be very helpful if we had an integration test for the behavior that the EarthAccessFile class enables.

@itcarroll
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itcarroll commented Sep 25, 2024

A change to repair damage done in #620 is to reintroduce a base class on EarthAccessFile (and I think io.IOBase might work), but it doesn't fix this issue.

@itcarroll
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Merged #832 in order to make way for a release. Note that the test surfacing this bug has been marked as an expected fail.

@pytest.mark.xfail(
reason="This test reproduces a bug (#610) which has not yet been fixed."
)
def test_earthaccess_file_getattr():
fs = fsspec.filesystem("memory")
with fs.open("/foo", "wb") as f:
earthaccess_file = EarthAccessFile(f, granule="foo")
assert f.tell() == earthaccess_file.tell()
# cleanup
fs.store.clear()

nikki-t added a commit that referenced this issue Oct 1, 2024
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type: bug Something isn't working
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