Install Themes: API call to api.wordpress.org fails under IE8/9 because of CORS

[ocean90]

Currently the API call to fetch themes fails with the message "No transport".

After some searching I found, that $.support.cors = true; should help. This still ends in an error with "Access is denied".

[nacin]

Okay, if the browser doesn't support CORS, we can proxy these through PHP, as we had been doing before.

[johnbillion]

Related: #27581

[nacin]

As indicated in #27581 we can also go the JSONP route. The API now supports the following:

• ?callback=
• tag: to be comma-separated rather than an array, to save on length
• fields: to be comma-separated rather than an array, to save on length (for this, it assumes all are true)

I'd suggest that everything be consolidated in apiCall; other areas shouldn't need to know tags should be imploded; it makes it harder to manipulate.

[adamsilverstein]

use wp-ajax and json api for apiCall

[adamsilverstein]

use wp-ajax and json api for apiCall

[adamsilverstein]

27639.patch​ is based on johnbillion's patch - added transient caching; tested in ie8, resolves the ticket issue;

[nacin]

I don't think we need transient caching for this. We're dealing with a fairly arbitrary features matrix and arbitrary searching... It would explode the database without much benefit. It's unlikely to see much crossover with someone else's results; meanwhile, the JS maintains a local cache for that particular person.

I'd still like to see an attempt at JSONP and avoiding the proxy.

That said, if we were to proxy, then we should use themes_api() and bring in the filters we lost in WP_Theme_Install_List_Table::prepare_items().

[nacin]

Also: A nonce isn't needed for a fetching action.

[adamsilverstein]

Replying to nacin:

I don't think we need transient caching for this. We're dealing with a fairly arbitrary features matrix and arbitrary searching... It would explode the database without much benefit. It's unlikely to see much crossover with someone else's results; meanwhile, the JS maintains a local cache for that particular person.

I'd still like to see an attempt at JSONP and avoiding the proxy.

That said, if we were to proxy, then we should use themes_api() and bring in the filters we lost in WP_Theme_Install_List_Table::prepare_items().

Thanks for the feedback, good point about the transient caching. I will give the JSONP approach a shot.

[jorbin]

I missed this being opened and instead posted to the original THX ticket. My proposed solution is not very different from Adams. I've posted it here though for posterity.

[nacin]

In 27961:

Theme Installer: Use JSONP for api.wordpress.org requests.

fixes #27639.

[adamsilverstein]

Replying to nacin:

In 27961:

Theme Installer: Use JSONP for api.wordpress.org requests.

fixes #27639.

Nicely done sir!

[nacin]

In 28126:

Theme Installer: Revert to proxying through PHP for WordPress.org API requests.

This is to ensure we have valid installation nonces, though we've run into this as a problem previously (see #27639, #27581, #27055).

A tad slower, but we gained speed in 3.9 by simplifying the request made to the API.

props ocean90.
fixes #27798.