Changed tempfile.NamedTemporaryFile mode to w

[H-Sorkatti]

Inside src/click/_termui_impl.py, the function get_pager_file delegates the creation of a tempfile to _tempfilepager, which returns a BinaryIO object of the opened file:

f = tempfile.NamedTemporaryFile(mode="wb", delete=False)
try:
    yield t.cast(t.BinaryIO, f), encoding, color
...

Which is called by _pager_contextmanager in

...
if pager_cmd_parts:
        if WIN:
            return _tempfilepager(pager_cmd_parts, color)
        return _pipepager(pager_cmd_parts, color)
...
    if WIN or sys.platform.startswith("os2"):
        return _tempfilepager(["more"], color)
    return _pipepager(["less"], color)

In the end get_pager_file

def get_pager_file(color: bool | None = None) -> t.Generator[t.TextIO, None, None]:
    ...
    with _pager_contextmanager(color=color) as (stream, encoding, color):
    # Split streams by capabilities rather than the abstract TextIO /
    # BinaryIO annotations: buffered text streams can be unwrapped to bytes,
    # while other streams are yielded as-is.
    wrapper: MaybeStripAnsi | None = None
        if _has_binary_buffer(stream):
            # Text stream backed by a binary buffer.
            wrapper = MaybeStripAnsi(stream.buffer, color=color, encoding=encoding)
            stream = wrapper
        try:
            # Narrow the BinaryIO | TextIO union that _pager_contextmanager
            # yields; the caller writes text to the pager.
            yield t.cast(t.TextIO, stream)
        ...

In the above yield t.cast(t.TextIO, stream) stream object will be BinaryIO, contradicting the TextIO annotation of the return value, all because it was created with the mode "wb" earlier.

Then if a caller tries: stream.write("some text") it will raise an exception:
TypeError: a bytes-like object is required, not 'str'

FIX:
In _tempfilepager, create the temp file with mode='w'

f = tempfile.NamedTemporaryFile(mode="w", delete=False)

Closes #3740

[H-Sorkatti]

@kdeldycke
I'm not AI by the way. This a genuine human fix. But of course, it's your library.

[kdeldycke]

@kdeldycke I'm not AI by the way. This a genuine human fix. But of course, it's your library.

Ah. Sorry for the confusion. Maintainers are overloaded with noise these past few months so I wrongly flagged that. Let me review your proposal then.

[kdeldycke]

OK this is confirmed as a regression from #1572 . And it was not caught because _tempfilepager has 0 test coverage.

[kdeldycke]

Just added tests to cover the regression and added a changelog entry. Also added test for color handling. This PR is ready to be merged upstream.