FLAC: legacy id3 tags error in flac.save_to write-back

[PandorasFox]

Reproducer

https://gist.github.com/PandorasFox/42a651962129e85b19491af8c0abefeb - uses ffmpeg to write out a short silent FLAC file, prepends id3 tags, reproduces when trying to embed a picture tag and write back

Summary

I have some old Pendulum flacs with id3 tags prepended to them - gross, but technically valid. This produces the following behaviors in lofty:

• parses fine, but then can't write back; errors with 'Attempted to write a tag to a format that does not support it"'
• if using remove_id3v2, errors with "File missing fLaC stream marker" - I assume something to do with loading back the file before writing when editing in place

Expected behavior

No response

Assets

No response

[Serial-ATA]

parses fine, but then can't write back; errors with 'Attempted to write a tag to a format that does not support it"'

This is expected, see https://github.com/Serial-ATA/lofty-rs/tree/main?tab=readme-ov-file#supported-formats. Some tags are read only, as I don't want to support writing tags that aren't officially supported by the format.

if using remove_id3v2, errors with "File missing fLaC stream marker" - I assume something to do with loading back the file before writing when editing in place

This isn't expected, though. The picture/Vorbis Comment writer isn't ID3v2 aware, since it's assumed that the ID3v2 tag was stripped before that point. I guess that assumption is wrong, I'll take a look

[Serial-ATA]

@PandorasFox can you test #609? It should fix both of your issues. If all's good I'll release 0.23.2

[PandorasFox]

@PandorasFox can you test #609? It should fix both of your issues. If all's good I'll release 0.23.2

Looks great! my repro tests pass with those changes.

Thank you so much; lofty has been wondrously helpful for vorbis-comment-ifying all my music