Avoid template rendering of action's parameter

[amitfin]

Goal

An action should get a template as an input so the action can render it internally. For example, the action needs to supply variables to the render function. (Actual example can be found here.)

Challenge

It seems that currently action's data parameters are always getting rendered to strings before calling the action (here).

What was tried

Changing the type of the parameter to string doesn't help because of the code here and here which translates string parameters to templates when they contain a Jinja expression.

Ugly workaround

Use string with a special template format of square brackets "[[ ... ]]" instead of curly brackets "{{ ... }}". The action changes the string to be a valid template string before rendering it.

Ask

Is there a way to avoid template rendering of action's parameter? Any thoughts or suggestions?

Proposal

Assuming there is currently no way to do so, here is a proposal:

1. Add data_raw dictionary for fields which shouldn't get rendered (allowing integrations to get the raw values). The core change is here.
2. Add raw option for the template selector. Using this option puts the value under the data_raw dictionary instead of the regular data dictionary. The frontend change is here.

(Both changes will be moved to PRs once the proposal gets approved.)

[farmio]

Same applies for knx. See home-assistant/core#128901 (comment)

[amitfin]

Added a "Proposal" section to the original post (it seems that currently there is no way to do it).