Build extension updater class

[fjarrett]

As first discussed in https://github.com/x-team/wp-stream-reports/issues/5, we need to include an updater inside core Stream that will handle updates for extensions from a centralized class.

This should integrate with the work being done on #396.

• Always check for updates, even if there is no license key.
• New version details should always be viewable, even if there is no license key.
• Show an alternate message in plugins screen if an update is available but no key is found (see screenshot below).
• Don't display the update in the Dashboard > Updates screen if there is no license key.
• Display a wp_die message if an update is attempted on an extension but the license ke is invalid or does not exist. The message should be relevant to the error that occurred (e.g. You have reached your site limit for automatic updates).

[shadyvb]

Always check for updates, even if there is no license key.> New version details should always be viewable, even if there is no license key.
New version details should always be viewable, even if there is no license key.

I think this is what's happening currently.

Don't display the update in the Dashboard > Updates screen if there is no license key.

This means we will have to use an alternate store to keep version updates separately from WP update API, which i think we should try to avoid. Instead, showing the notice/error if the user tries to update a premium extension, as in:

Display a wp_die message if an update is attempted on an extension but the license key is invalid or does not exist.
The message should be relevant to the error that occurred (e.g. You have reached your site limit for automatic updates).

should be sufficient to remind the user he needs to connect the site to his premium account, and would work using the standard update api integration of WP, for stability.

@fjarrett What do you think ?

[fjarrett]

@shadyvb I totally agree. Sounds great!

[fjarrett]

@shadyvb Will it be possible for this to be delivered today? Hoping to start thorough testing tonight with the whole team.

[fjarrett]

@shadyvb When can we start testing this?

[shadyvb]

@fjarrett I'll start cracking at this right now, been waiting for @c3mdigital to give the green light but seems he's got a lot on his plate.
I'll be working on the old updater.php.

[shadyvb]

@fjarrett This is as far as i can get with the notice, since the text is hardcoded, i can only add to it.

[shadyvb]

@fjarrett FYI, Now the update won't be attempted to begin with, if there is no license key, as there won't be a package URL that WordPress can attempt to download.
This change also hides any updates from dashboard>updates if no license key exists.

[shadyvb]

@fjarrett Since WordPress is handling download of package URLs automatically, i don't think i have a chance of tapping into the process and providing meaningful error messages.

[shadyvb]

Scratch that, found upgrader_source_selection, trying to utilize it..

[fjarrett]

@shadyvb So are you saying we won't be able to show updates are available at all unless a license key is in the DB? The hope would be that merely checking for the latest version would not require any authentication.

[shadyvb]

No, the update will show ( as in the screenshot ) but users won't be able to actually hit 'Update' because there is no package url, ie: WordPress does not know where to update this from. Which is actually what we need.

[fjarrett]

@shadyvb OK got it.

[shadyvb]

@fjarrett I don't think the last Task can be done, have dived in the code and WP does not offer proper actions/filters to hook into the download process if things go bad.
Also i think it is not good to wp_die in such cases, since the user might be bulk-updating stuff and this would break the process.

If you agree, I'll issue a PR to get this one finished, finally.

[shadyvb]

@fjarrett PR issued #450