disable universal newlines

[melbaa]

Hello,

On windows, bumpver ends up always rewriting files with '\r\n' endings due to universal newlines in text mode. The PR disables this.

In more detail, universal newline text mode always returns '\n' to the code, but ends up translating it to '\r\n' on write. This causes bumpver to fail to preserve the original newlines.

[mbarkhau]

I would have expected the behaviour to be that the line endings are preserved as is in the file, so this is surprising to me. I'm not sure why this would be OS specific.

Do you have time to add a test case for this?

[melbaa]

No clue about the test, but I know how to show the newline translation from opening files in text mode with universal newlines.

Note how in both cases .read() returns '\n'.

import platform
assert platform.system() == 'Windows'
assert platform.python_version() == '3.10.1'

# only shows newlines being translated
import io
buffer = io.BytesIO(b'\r\n')
txt = io.TextIOWrapper(buffer)
assert txt.read() == '\n'
txt.write('\n')
txt.flush()
assert buffer.getvalue() == b'\r\n\r\n'

# this is similar to what happens in practice. a '\n' ends up a '\r\n' in the new file
import io
input_buffer = io.BytesIO(b'\n')
txt = io.TextIOWrapper(input_buffer)
assert txt.read() == '\n'

output_buffer = io.BytesIO()
txt = io.TextIOWrapper(output_buffer)
txt.write('\n')
txt.flush()
assert output_buffer.getvalue() == b'\r\n'

https://docs.python.org/3/glossary.html#term-universal-newlines https://docs.python.org/3/library/functions.html?highlight=newline#open

[mbarkhau]

I finally had some time to look at this and it appears you are correct.