def test_forward_does_not_automatically_copy_existing_file_content(
self) -> None:
path = self.make_empty_file()
path.write_bytes(b"hello world")
output = io.BytesIO()
with forward_log_file(path, output_file=output):
self.assertEqual(output.getvalue(), b"")
def test_forward_copies_existing_file_content_after_poll(self) -> None:
path = self.make_empty_file()
path.write_bytes(b"hello world")
output = io.BytesIO()
with forward_log_file(path, output_file=output) as forwarder:
forwarder.poll()
self.assertEqual(output.getvalue(), b"hello world")
def test_forward_does_not_automatically_copy_concurrent_appends(self) -> None:
path = self.make_empty_file()
output = io.BytesIO()
with forward_log_file(path, output_file=output):
self.assertEqual(output.getvalue(), b"")
with open(path, "ab") as file:
file.write(b"hello")
file.flush()
self.assertEqual(output.getvalue(), b"")
def test_polling_forward_flushes_output_buffer(self) -> None:
path = self.make_empty_file()
unbuffered_output = io.BytesIO()
# HACK(strager): BufferedWriter requires RawIOBase, but BytesIO inherits
# from IOBase, not RawIOBase. BufferedWriter seems to work fine with
# BytesIO though, and CPython's test suite even covers this use case:
# https://github.com/python/cpython/blob/v3.6.5/Lib/test/test_io.py#L1648-L1650
raw_output = typing.cast(io.RawIOBase, unbuffered_output)
buffered_output = io.BufferedWriter(raw_output, buffer_size=1024)
with forward_log_file(path, output_file=buffered_output) as forwarder:
with open(path, "ab") as file:
file.write(b"hello")
file.flush()
forwarder.poll()
self.assertEqual(unbuffered_output.getvalue(), b"hello")
def test_polling_forward_copies_concurrent_appends(self) -> None:
path = self.make_empty_file()
output = io.BytesIO()
with forward_log_file(path, output_file=output) as forwarder:
self.assertEqual(output.getvalue(), b"")
with open(path, "ab") as file:
file.write(b"hello")
file.flush()
forwarder.poll()
self.assertEqual(output.getvalue(), b"hello")
file.write(b"world")
file.flush()
forwarder.poll()
self.assertEqual(output.getvalue(), b"helloworld")