🪟📁📄 Ability to enforce windows compatible file names on the server about server

[tobiasKaminsky]

Subscribing myself, as I think this is then also a task for clients.

• If server returns a specific error message, clients should show a correct info
• if setting is enabled via capabilities, clients can directly prohibit renaming/creating such a file

[susnux]

@tobiasKaminsky we need this implemented / fixed on the clients, server and WebUI are already done:

• Desktop: nextcloud/desktop#6447
• Android: nextcloud/android#12576
• iOS: nextcloud/ios#2802

Implementation: Get the capability "forbidden_filename_characters" from the files app. This is an array of forbidden characters (could be multibyte characters, so it is an array of strings). If any of the strings in the array matches the filename it is considered invalid.

[SystemKeeper]

Besides some characters not allowed on windows, there are more rules that need to be taken into account, e.g. a Filename is also not allowed to end with a dot or a space. There are also some reserved filenames.
See https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file#naming-conventions for details.

[susnux]

Yes but having the forbidden characters implemented in clients is a good first step and also allows to configure other compatibility (like with some filesystems that forbid just :).

See https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file#naming-conventions for details.

This is also only partially true, Windows supports a lot of naming things, but the Explorer simply does not, like trailing . is working just win32 API needs the ? flag to disable path normalization (and of course Explorer fails to handle it).
Just like with Mac where some buggy GUI application forbid files with colon in the name, while on OS layer this is pretty fine.

But we probably should still enforce the character + the trailing space / dot rules. About the path length we can not do much, that depends on the users mount point and file type (e.g. for spreadsheets the table name counts into the path length 🤦).