Investigate file-like objects in FTP transfers

[nicolasCtd]

The Vortex codebase contains several references to file-like objects. For example in src/vortex/tools/systems.py:

vortex/src/vortex/tools/systems.py

Lines 1647 to 1654 in cace380

	def is_iofile(self, iocandidate):
	"""Check if actual **iocandidate** is a valid filename or io stream."""
	return iocandidate is not None and (
	(isinstance(iocandidate, str) and self.path.exists(iocandidate))
	or isinstance(iocandidate, io.IOBase)
	or isinstance(iocandidate, io.BytesIO)
	or isinstance(iocandidate, io.StringIO)
	)

and also in the tests:

vortex/tests/test_twistednet/test_ftpclient.py

Lines 53 to 60 in cace380

	ftpc = self.new_ftp_client()
	with self.assertRaises(RuntimeError):
	ftpc.pwd()
	ftpc.fastlogin(self.user, self.password, delayed=False)
	self.assertEqual(ftpc.logname, 'testlogin')
	with ftpc:
	self.assertEqual(ftpc.pwd(), '/')
	testdata = io.BytesIO()

The goal of this ticket is to clarify the current status of this feature.

• Is support for file-like objects fully implemented?
• If so, what is the intended way to use it? Are there any examples or documentation?
• Is this functionality actually used in operational, or is it only present for tests or legacy reasons?
• If the implementation is incomplete, should it be completed or clean up the code by removing the feature?

[nicolasCtd]

The test script below demonstrates that ftput and ftget support file-like objects.

In the first part of the test, a file-like object is uploaded to the remote file "testIO" on hendrix using ftput. In the second part, the content of this remote file is retrieved into a file-like object using ftget.

import io
from vortex.tools.systems import OSExtended

class TestSystem(OSExtended):
    def __init__(self):
        super().__init__()

logname = "coutandn"
port = None
hostname = "hendrix.meteo.fr"

system = TestSystem()

remote_file = "testIO"
content = b"Test of the ftput/ftget methods with a file-like object"

# 1. Upload a file-like object to a remote file
# -----------------------------------------------------------------------------
system.ftput(
    source=io.BytesIO(content),
    destination=remote_file,
    hostname=hostname,
    logname=logname,
    port=port,
    cpipeline=None,
    sync=False,
)

# 2. Download a remote file to a file-like
# -----------------------------------------------------------------------------
destination = io.BytesIO()

system.ftget(
    source=remote_file,
    destination=destination,
    hostname=hostname,
    logname=logname,
    port=port,
    cpipeline=None,
)

destination.seek(0)
downloaded = destination.read()

assert downloaded == content, f"Expected content {content}, got {downloaded}"

print("OK:", downloaded)