Deploying process model with new rule inputs for an expression rule which hasn't been updated

As long as you have used dictionary structure to pass the existing inputs of that expression rule also if you don't pass the expression rule's new input it won't break the rule individually. It will be fine to deploy the process.

Yep, Kunal is exactly right. Just to explain further, dictionary syntax means that you provide the parameter name and value for each input. Suppose you have an expression rule that takes two inputs: status and user. Dictionary syntax means setting up the rule like this:

rule!MY_Rule(
  status: pv!statusVar,
  user: loggedInUser()
)

Suppose you then update your expression rule and process model to add a new parameter like this:

rule!MY_Rule(
  status: pv!statusVar,
  user: loggedInUser(),
  newParam: true
)

The way dictionary syntax works is that any parameters are only applied if they match in the rule. In Development, you have this parameter saved to your expression rule, so it uses the value you provide. In Production, newParam doesn't exist, so it is simply ignored.

Yep, Kunal is exactly right. Just to explain further, dictionary syntax means that you provide the parameter name and value for each input. Suppose you have an expression rule that takes two inputs: status and user. Dictionary syntax means setting up the rule like this:

rule!MY_Rule(
  status: pv!statusVar,
  user: loggedInUser()
)

Suppose you then update your expression rule and process model to add a new parameter like this:

rule!MY_Rule(
  status: pv!statusVar,
  user: loggedInUser(),
  newParam: true
)

The way dictionary syntax works is that any parameters are only applied if they match in the rule. In Development, you have this parameter saved to your expression rule, so it uses the value you provide. In Production, newParam doesn't exist, so it is simply ignored.

I thought that would be the case, but as it's going to be deployed to PROD I just wanted to make sure. Thanks both for the responses, it's really appreciated.