Show a warning when saving a file with encoding that cannot encode all characters

[jrieken]

re #44292

• in window 1, have a file with hellö world
• save that file with 'windows 1256' encoding
• copy that file into window 2
• in window 2, reopen that file (from utf8) to windows 1256
• 🐛 the ö got lost

[jrieken]

Hm, maybe an issue with that encoding... When I close and re-open in the same window this happens but it doesn't happen after saving giving me the wrong impression of success

[bpasero]

Yes, this is because we do not remember the encoding for files when closing and reopening them.

[jrieken]

closing and reopening them

No, it's not that. When I do re-open with encoding it's garbage, likely because the character cannot be encoded

[bpasero]

@jrieken ah yeah, it seems what is needed is a way to find out if the characters in the document can be encoded or not with the selected encoding. Similar to this:

[bpasero]

Depends on pillarjs/iconv-lite#53