Package manager silently fails to install mod, does not offer FTP when needed

[ke]

Version: 2.0.6

How to reproduce: try to install a mod via the package manager that modifies some files that are not writable by the webserver that runs SMF.

Expected behavior: form asking for FTP access data appears, package manager uses FTP to install package.

Actual behavior: FTP form does not appear, package manager reports success in installing the mod, but the mod is not installed as can be verified on the "browse packages" page or by inspecting the files.

Reproducibility: apparently not always - what is the criterion SMF uses for checking whether or not to offer the FTP form?

Workaround: prior to installation, make all required files and directories writable by web server

Discussion: This bug has existed for quite a while (see e.g. here for an instance of a user running into it) and is very confusing and annoying, should be fixed with priority.

[Arantor]

The criteria used by SMF is simply the basic is_writable test in PHP. If that's returning true for files, the package manager can't know that, actually magically the files aren't actually writable.

Don't see how it *can* be fixed in the current SMF architecture, isn't going to get fixed in 2.0, can't see how it can be fixed in 2.1, virtual non-issue for 3.0 whose architecture is changing to avoid file edits.