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Opened 3 years ago

Last modified 10 months ago

#22355 new enhancement

Template stack - Beyond parent/child theme relationships

Reported by: johnjamesjacoby Owned by:
Milestone: Awaiting Review Priority: normal
Severity: normal Version:
Component: Themes Keywords: has-patch
Focuses: Cc:

Description (last modified by johnjamesjacoby)

Problem

Robust plugins (BuddyPress, bbPress, et all) are unable to break out of the parent/child restrictions that WordPress imposes on template output. For these plugins to include their own template parts, elaborate code must be written to hook into several different execution points, requiring an intimate knowledge of the inner workings of WordPress's template loading system.


Solution

Create a stack of template locations, and allow WordPress to transverse this array following the same STYLESHEETPATH/TEMPLATEPATH order it always has, while also enabling additional paths to be added with a priority (similar to the filters API.)


Details

The attached patch includes two new functions in wp-includes/template.php:

  • register_template_stack()
  • get_template_stack()

Register template stack is a wrapper for the 'template_stack' filter. get_template_stack() is a variation of apply_filters() that returns the array of filtered template locations.

A modification to wp-settings.php calls register_template_stack() two times, passing get_stylesheet_directory() and get_template_directory() as callbacks, to initialize the core parent/child relationship, ensuring complete backwards compatibility.


Result

This allows for plugins to register additional paths in the template loader hierarchy, and enables plugins that may come with their own default template parts the option of registering a fallback template location.

This works with both locate_template() and get_template_part(), and has the added benefit removing duplicate items inside of get_template_stack(), resulting in avoiding an additional file system check should the parent and child themes be the same.

Attachments (5)

22355.patch (3.9 KB) - added by johnjamesjacoby 3 years ago.
22355.2.patch (4.0 KB) - added by johnjamesjacoby 3 years ago.
Reverse lookup (name to stack) and break out of both loops
22355.3.patch (4.1 KB) - added by meloniq 2 years ago.
Patch according to @scribu and @chacha102 suggestions: uses separate global instead of filters api, pass path instead of callback, added 'remove' and 'has' functions
27322.diff (2.3 KB) - added by rmccue 18 months ago.
Patch from #27322
22355.4.patch (3.4 KB) - added by obenland 10 months ago.

Download all attachments as: .zip

Change History (63)

@johnjamesjacoby3 years ago

comment:1 @obenland3 years ago

  • Cc obenland added

comment:2 @JustinSainton3 years ago

  • Cc justinsainton@… added

comment:4 @curtismchale3 years ago

  • Cc curtis@… added

comment:5 @mordauk3 years ago

  • Cc pippin@… added

comment:6 @MikeSchinkel3 years ago

  • Cc mike@… added

comment:7 @johnjamesjacoby3 years ago

  • Description modified (diff)

comment:8 @stephenh19883 years ago

  • Cc contact@… added

comment:9 @mercime3 years ago

  • Cc mercijavier@… added

comment:10 follow-up: @scribu3 years ago

A usage example from start to finish would be helpful.

@johnjamesjacoby3 years ago

Reverse lookup (name to stack) and break out of both loops

comment:11 in reply to: ↑ 10 @johnjamesjacoby3 years ago

Replying to scribu:

A usage example from start to finish would be helpful.

Imagine a plugin registers a custom post type 'foo' and wants to bundle templates for twentytwelve support. This plugin would:

  • Call: register_theme_stack( 'my_plugin_twentytwelve_template_path', 10 );
  • Now, /plugins/my-foo/twentytwelve/single-foo.php is in the stack.
  • locate_template() finds a match in the plugin directory.
  • Profit.

comment:12 follow-up: @scribu3 years ago

And you could control the order (parent theme, child theme, plugin) via the priority arg. Got it.

Instead of:

register_template_stack( 'get_stylesheet_directory', 10 );

why couldn't you do:

register_template_stack( get_stylesheet_directory(), 10 );

since the callback just returns a path, which needs to be computed only once.

Last edited 3 years ago by scribu (previous) (diff)

comment:13 @wpmuguru3 years ago

+1 - I've used templates located im plugins several times for a variety of reasons.

comment:14 @mordauk3 years ago

+1 as well. I've built templating systems into plugins as well and this would dramatically cut down the work load.

comment:15 @ryanduff3 years ago

  • Cc ryan@… added

comment:16 in reply to: ↑ 12 @johnjamesjacoby3 years ago

Replying to scribu:

why couldn't you do (...) since the callback just returns a path, which needs to be computed only once.

I went the callback route because it came with the filters API; either approach would work.

comment:18 @mzaweb3 years ago

  • Cc mzaweb added

comment:19 @alexvorn23 years ago

  • Cc alexvornoffice@… added

comment:20 @DrewAPicture3 years ago

  • Cc xoodrew@… added

Pretty neat, and we drop STYLESHEETPATH and TEMPLATEPATH in the process. +1

comment:21 follow-ups: @johnbillion3 years ago

I like this idea.

Is there really a need for the register_template_stack() wrapper function? I'd prefer to stick with add_filter(), which is self explanatory.

comment:22 @maor3 years ago

  • Cc maorhaz@… added

comment:23 in reply to: ↑ 21 @johnjamesjacoby3 years ago

Replying to johnbillion:

I like this idea.

Is there really a need for the register_template_stack() wrapper function? I'd prefer to stick with add_filter(), which is self explanatory.

add_filter() alone would work. The reason to use a dedicated function is to make it API agnostic. Should we want to move it off of the filters API later, we can do so without changing the name of the function or it's parameters.

comment:24 @jondavis3 years ago

  • Cc jondavis added

comment:25 @sabreuse3 years ago

  • Cc sabreuse added

comment:26 @DrewAPicture3 years ago

#23180 was marked as a duplicate.

comment:27 @kovshenin3 years ago

  • Cc kovshenin added

comment:28 @tarasm3 years ago

  • Cc tarasm@… added

comment:29 @meloniq3 years ago

  • Cc meloniq@… added

comment:30 in reply to: ↑ 21 @chacha1023 years ago

Replying to johnbillion:

Is there really a need for the register_template_stack() wrapper function? I'd prefer to stick with add_filter(), which is self explanatory.

But it isn't a filter. The values of previous function aren't passed to the next function. If I understand correctly, I don't think anything is passed to the function at all.

Right now the filter API is simply a storage mechanism, which doesn't seem right.

comment:31 @chacha1023 years ago

  • Cc chacha102 added

comment:32 @pauldewouters2 years ago

  • Cc pauldewouters@… added

@meloniq2 years ago

Patch according to @scribu and @chacha102 suggestions: uses separate global instead of filters api, pass path instead of callback, added 'remove' and 'has' functions

comment:33 @meloniq2 years ago

Above patch uses way of registering locations suggested by @scribu : add_template_stack( get_template_directory(), 12 ); , stop to use filters api as suggested @chacha102 - uses $wp_template_stack global, and adds functions to remove and check for existence of template location.

comment:34 @mindctrl2 years ago

  • Cc dailyrants@… added

comment:35 @iandunn2 years ago

  • Cc ian.dunn@… added

comment:36 @alex-ye2 years ago

  • Cc nashwan.doaqan@… added

comment:37 @chipbennett2 years ago

  • Cc chip@… added

comment:38 @emzo2 years ago

  • Cc wordpress@… added

comment:39 @sumobi2 years ago

  • Cc sumobi added

comment:40 @fjarrett2 years ago

  • Cc fjarrett@… added

comment:41 @westonruter2 years ago

  • Cc weston@… added

comment:42 @talbet2 years ago

  • Cc talbet.fulthorpe@… added

comment:43 @atimmer23 months ago

  • Cc atimmermans@… added

comment:45 @nacin18 months ago

#27322 was marked as a duplicate.

@rmccue18 months ago

Patch from #27322

comment:46 follow-up: @rmccue18 months ago

Added a simpler patch that handles this without adding a multitude of extra functions. It also adds a theme_url function as per #18302, since it makes a lot of sense to introduce that at the same time.

IMO, there no reason we should store this in a global. Doing it there creates a lot of extra code over the simplicity of just filtering an array.

comment:47 @casben7918 months ago

+1 for the patch by rmccue looks like a very neat solution to this and #13239

comment:48 @rmccue17 months ago

I'm going to assume we're too late for 3.9 here, but does anyone want to weigh in on the above patch? I'd like to aim for 4.0-early if we're +1 here. nacin seems to like the idea so far, anyone else have thoughts? :)

comment:49 @ircbot10 months ago

This ticket was mentioned in IRC in #wordpress-dev by rmccue. View the logs.

@obenland10 months ago

comment:50 @obenland10 months ago

  • Milestone changed from Awaiting Review to 4.1

I really like the idea.

Added an updated patch, where theme_url() lives with other *_url() template tags, wp_template_directories() is get_template_directories() to reflect the nomenclature in template.php, and some added docs.

I wonder if we should restrict get_template_directories() to only allow directories to be added after stylesheet and template directories, not before.

comment:51 follow-up: @georgestephanis10 months ago

Related: https://core.trac.wordpress.org/attachment/ticket/18302/18302.14.diff -- there's some discussion on that ticket about the desire for the normal inheriting function, but also one where you can specify you want the parent theme url and it to not be overrideable.

comment:52 in reply to: ↑ 51 @rmccue10 months ago

Replying to georgestephanis:

Related: https://core.trac.wordpress.org/attachment/ticket/18302/18302.14.diff -- there's some discussion on that ticket about the desire for the normal inheriting function, but also one where you can specify you want the parent theme url and it to not be overrideable.

I kind of disagree with not having it overridable, but we've also noticed the need to "skip" to the parent. We could possibly add a skip_levels argument, default to 0, where parent theme is $skip_levels = 1

comment:53 in reply to: ↑ 46 @johnjamesjacoby10 months ago

Replying to rmccue:

Added a simpler patch that handles this without adding a multitude of extra functions. It also adds a theme_url function as per #18302, since it makes a lot of sense to introduce that at the same time.

IMO, there no reason we should store this in a global. Doing it there creates a lot of extra code over the simplicity of just filtering an array.

If all we want is the ability to short-circuit the template loading process with a filter, there are easier ways to do that than this. The extra functions are important for encouraging plugin and theme libraries to announce to the application that they are introducing a new template directory location, to allow other libraries to interact with it accordingly.


Example: both BuddyPress & bbPress are active, and both introduce their own default template locations. A new theme is activated that wants to unhook the default BuddyPress & bbPress default template locations, and completely own the output experience. If BuddyPress & bbPress are forced to register their locations as callbacks, they are much easier to manipulate. Without registering them, plugin and theme authors will need to guess at what each template location is for, and guess at how to interact with it.

Example: both BuddyPress & bbPress are active, again both introducing default template locations. I write a plugin that includes a brand new set of template parts for handling what BuddyPress Member Profiles look like, with an emphasis on forum topics. In my plugin, I should be able to announce a new template location ahead of BuddyPress & bbPress, so my template parts are located first.

In theory, each template and part could be registered (to avoid a whole mess of file_exists() checks) but that's a lot of additional work for not much gain.


We should try to shy away from function names like get_template_directories(). The theme/template/stylesheet nomenclature is already messy, and it starts to collide with existing function names like register_theme_directory(), search_theme_directories(), etc...

The revised approach in the most recent patches is better than what's in core today, but provides less structure than I originally proposed. I think the _stack naming conventions proposed in my original patch are more clear, and more accurately represent the complex relationships that plugins have with themes than yet-another-filter at the end of the template funnel.

comment:54 @slackbot10 months ago

This ticket was mentioned in Slack in #core by georgestephanis. View the logs.

comment:55 @slackbot10 months ago

This ticket was mentioned in Slack in #core by georgestephanis. View the logs.

comment:56 @slackbot10 months ago

This ticket was mentioned in Slack in #core by jjj. View the logs.

comment:57 @johnbillion10 months ago

#30288 was marked as a duplicate.

comment:58 @johnbillion10 months ago

  • Milestone changed from 4.1 to Awaiting Review

I don't think this was ever on the cards for 4.1.

We need to consider this along with other tickets such as #14310 and #12877.

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