Port Add a variable (variable_add) to D8

I worked on it and created a new pull request: https://github.com/fago/rules/pull/121

Added some comments at the PR. We'll have to do some more things to get it ported though - maybe as a start we should add @todo for all not-yet ported action callbacks from d7, i.e. in particular info alter and options stuff.

https://github.com/fago/rules/pull/121 is already merged. Can we close that issue or are there still open tasks here?

Sorry, forgot to close this indeed.

That implemenation is not complete as it does not take care of properly passing through metadata depending on the given context. -> it misses porting of the info_alter() logic.

working on it today at Milano Drupal Sprint.

can't be done right now

We need #2456829: Context definition needs to be updated before execution solved for being able to update override getContextDefinitions() accordingly.

#2456829: Context definition needs to be updated before execution is done - see EntityFetchByField as example.

I think this was finished. Am I missing something? Is there still something left to do here?

#2456829: Context definition needs to be updated before execution added the ability to refine context definitions.

#2658960: Create the loop action expression plugin update the VariableAdd action to use the refineContextDefinitions() method.

We have tests for this action.

So what is missing, if anything?