[jira] [Created] (ARROW-10998) [C++] Filesystems: detect if URI is passed where a file path is required and raise informative error

["Joris Van den Bossche (Jira)" <ji...@apache.org>]

Joris Van den Bossche created ARROW-10998:
---------------------------------------------

             Summary: [C++] Filesystems: detect if URI is passed where a file path is required and raise informative error
                 Key: ARROW-10998
                 URL: https://issues.apache.org/jira/browse/ARROW-10998
             Project: Apache Arrow
          Issue Type: Improvement
          Components: C++, Python
            Reporter: Joris Van den Bossche


Currently, when passing a URI to a filesystem method (except for {{from_uri}}) or other functions that accept a filesystem object, you can get a rather cryptic error message (eg in this case about "No response body" for S3, in the example below). 

Ideally, the filesystem object knows its own prefix "scheme", and so can detect if a user is passing a URI instead of file path, and we can provide a nicer error message.

Example with S3:

{code:python}
>>> from pyarrow.fs import S3FileSystem
>>> fs = S3FileSystem(region="us-east-2")
>>> fs.get_file_info('s3://ursa-labs-taxi-data/2016/01/')
...
OSError: When getting information for key '/ursa-labs-taxi-data/2016/01' in bucket 's3:': AWS Error [code 100]: No response body.

>>> import pyarrow.parquet as pq
>>> table = pq.read_table('s3://ursa-labs-taxi-data/2016/01/data.parquet', filesystem=fs)
...
OSError: When getting information for key '/ursa-labs-taxi-data/2016/01/data.parquet' in bucket 's3:': AWS Error [code 100]: No response body.
{code}

With a local filesystem, you actually get a not found file:

{code: python}
>>> fs = LocalFileSystem()
>>> fs.get_file_info("file:///home")
<FileInfo for 'file:///home': type=FileType.NotFound>
{code}

cc [~apitrou]



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