The error file is created even when gallery-dl successfully downloads all files

[lyubomyr-shaydariv]

Steps to reproduce

For gallery-dl version as of 1.30.10:

gallery-dl --error-file errors '<ANY_WORKING_URL>' \
    || echo 'fail'

Actual results

If the gallery-dl command from the above steps succeeds, the right operand of the shell operator || is not executed as expected, but the file errors is created empty.

Expected results

It would be nice to postpone creating the errors file and writing errors to it until the first error occurs.

[mikf]

--error-file is currently implemented as a logging FileHandler, which immediately opens/creates a file.

[lyubomyr-shaydariv]

@mikf thank you for clarification.

For Bash users who are interested in a temporary workaround, please use ifne and tee from the moreutils package:

gallery-dl --error-file >(ifne tee errors) '<ANY_WORKING_URL>' \
    || echo 'fail'

[mikf]

https://docs.python.org/3/library/logging.handlers.html#logging.FileHandler

If delay is true, then file opening is deferred until the first call to emit().

Huh, guess I should have actually read the docs...

[lyubomyr-shaydariv]

@mikf Thanks for the insight! The delay option is exactly what's needed for the fix, so I mapped an optional defer kwarg (defaults to false; "defer" seems to be a better word in English) that's mapped to delay. Please see #8622.