unable to alter env variable

It seems like we could solve this requirement by adding a new YAQL function.

Something like this:

    <% environment_update(dict) %>

We might prefer a way to update just a single key...

    <% environment_update(key, value) %>

The implementation should be easy, so I added the low-hanging-fruit tag. The hardest part here is probably coming up with a sensible API for the YAQL function.

I'm not sure it's a good idea in general. We assumed from the very beginning that it should be an immutable structure and in many places in the code we use that assumption. Also remember that Mistral passes an environment into sub workflows. How is that supposed to work if it becomes mutable? Should it be the same structure (i.e. modifications in sub workflows are seen in parents) or we need to copy?

I'd prefer to look at your use case first more carefully. Maybe there's a way to address it now by using existing mechanisms.

Marked it "Incomplete" for now since it's not 100% clear how to make the change properly. And we also need to look at the mentioned use case first.