Exclude relationship behaviour doesn't work as expected when there are multiple implied relationships

[max-arshinov]

Description

This is a follow-up for #303. It looks like Structurizr always selects the first relationship as an implied relationship, even when this relationship is excluded.

Steps to reproduce

1. Create a workspace using a code example below

Expected behaviour

• r1 is hidden
• r2 is shown as an implied relationship

Actual behaviour

• both r1 and r2 are hidden

Screenshot

Code sample

workspace {
    model {
        customer = person "User"
        
        system1 = softwareSystem "System 1" {
            container1 = container "Container 1"
            container2 = container "Container 2"
        }

        system2 = softwareSystem "System 2" {
            container3 = container "Container 1"
            container4 = container "Container 2"
        }

        r1 = container3 -> container1 "3 -> 1"
        r2 = container4 -> container2 "4 -> 2"
    }   
    
    views {
        systemContext system1 {
            include system1 system2
            exclude r1
            include r2
            autolayout
        }
        theme default
    }
}

Configuration

No response

Severity

Major

Priority

Medium

Resolution

I have no budget, please fix this for free

More information

No response

[simonbrowndotje]

This is as expected; see https://github.com/structurizr/dsl/tree/master/docs/cookbook/implied-relationships#multiple-implied-relationships for an explanation.

[max-arshinov]

Even if I explicitly excluded the first relationship from the view?

[simonbrowndotje]

Yes - if you inspect the model (e.g. the JSON version of the workspace), you'll see that relationship 4 -> 2 does not get propagated to the system level, which is as designed with CreateImpliedRelationshipsUnlessAnyRelationshipExistsStrategy. You'll need to use a different implied relationships strategy if you want different behaviour; for example:

workspace {

    !script groovy {
        workspace.model.impliedRelationshipsStrategy = new com.structurizr.model.CreateImpliedRelationshipsUnlessSameRelationshipExistsStrategy();        
    }

    model {
        customer = person "User"
        
        system1 = softwareSystem "System 1" {
            container1 = container "Container 1"
            container2 = container "Container 2"
        }

        system2 = softwareSystem "System 2" {
            container3 = container "Container 1"
            container4 = container "Container 2"
        }

        r1 = container3 -> container1 "3 -> 1"
        r2 = container4 -> container2 "4 -> 2"
    }   
    
    views {
        systemContext system1 {
            include system1 system2
            exclude r1
            include r2
            autolayout
        }
        theme default
    }
}

[max-arshinov]

Understood. I can work around this. However, it still feels like this behavior is unexpected. I need to know the implementation details of Structurizr to understand it. Also, I still think that the default strategy for implied relationships should factor in excluded relationships. Anyway, thank you for the clarification.