If you go to https://extensions.gnome.org/ and try to install an extension by clicking on the on/off slider on the extension page and something goes wrong there is feedback to the user. One is left with the impression the extension actually installed when in fact it didn't. But more to the point there is no diagnostic information as to why it didn't work. At a minimum there should at least be user feedback the install failed, extra points for diagnostic information.

Here is a write up of my most recent experience trying to install an extension:

Click on the on/off slider, get prompted to install the extension, click
OK. Then nothing, it doesn't get installed. Confirmed by looking at my
installed extensions list and by looking in
~/.local/share/gnome-shell/extensions/

O.K. fire up Firebug, look at what it's doing, oh it asking DBus to to
the install, fire up dbus-monitor --session, see this:

> method call sender=:1.291 -> dest=:1.277 serial=128 path=/org/gnome/Shell; interface=org.gnome.Shell.Extensions; member=InstallRemoteExtension
>    string "window-list@gnome-shell-extensions.gcampax.github.com"
> error sender=:1.277 -> dest=:1.291 error_name=org.gnome.Shell.DownloadExtensionError reply_serial=128
>    string "404"

Hmm 404, not found

Why doesn't the error get percolated back up to the user instead of just
being silent?

Google at bit and find this:

https://github.com/gcampax/gnome-shell-extensions/tree/master/extensions/window-list

I guess that's what it's trying to install, why wasn't it correct in the
first place?

I tried grabbing the files from the repo and putting them under
~/.local/share/gnome-shell/extensions/window-list@gcampax.github.com but
that didn't work either.

Is there some documented process for manually installing an extension? I couldn't find one.