[chain] Add new placeholder.

[itsdarrylnorris]

Problem / Motivation

A very common use case of the Placeholder is having the ability of finding the location of a theme / module or a profile.

Solution

Provide the ability of having this as placeholder and it should provide you the location of the project.

The syntax should be similar to this:

• @{{theme_path('casper')}}
• @{{module_path('pathauto')}}
• @{{profile_path('thunder')}}

[jmolivas]

Another option is to:

• Execute php funcitons
  @{{drupal_get_path('theme','casper')}}
• Call a method within a service
  @{{service_name.method('agr1', 'agr2', 'agr3')}}

[novia713]

just a bit offtopic, but i would like to say i don't feel intuitive nor like the syntax for placeholders here.
i don't like %{{ }} nor @{{ }}

why can't it be something more simple?

[jmolivas]

@novia713 we needed to add a key that is not possible to be present on the YAML definition.

[jmolivas]

I like to make sure we do not get confused with service having . on the name:

• instead of this:
  @{{service_name.method('agr1', 'agr2', 'agr3')}}
• we could implement somehitng like this:
  • @{{service_name->method('agr1', 'agr2', 'agr3')}}
  • @{{service('service_name').method('agr1', 'agr2', 'agr3')}}
  • @{{service_name|method('agr1', 'agr2', 'agr3')}}