Why the heck don't we have global variables?

Archive Month of "What the heck?!" (2020)
67

So how would people want to see this work ? It’s important to know that we cannot have functions available in templates to store variables because rendering a template cannot have a side effect. They obviously would be able to access it.

Have a script action:

action:
 - variables.store:
     key: my_var
     type: datetime
     value: >
      {% if is_state("sun.sun", "above_horizon") %}
        {{ states.input_datetime.something_1.state }}
      {% else %}
        {{ states.input_datetime.something_2.state }}
      {% endif %}

If the value does not match the type, it would stop the script there with a fatal error.

And then in a template you can use:

{{ variables.my_var }} (this would be datetime object)