C4PlantUMLExporter mistakes container and component description for technologies when only description is present

[Paul Colby]

Description

The official Structurizr DSL reference syntax for containers and components is:

container <name> [description] [technology] [tags]
component <name> [description] [technology] [tags]

Though to be more precise, that is slightly ambiguous, and most Structurizr tooling interpret it as:

container <name> [description [technology [tags]]]
component <name> [description [technology [tags]]]

Which is to say, tags is the most-optional, followed-by technology, then description. This can be seen in ContainerParser::parse() and ComponentParser::parse().

However, when C4PlantUMLExporter::writeElement() generates C4-PlantUML Container(...) and Component(...) procedure calls, if technology is not set, then description ends up in the technology argument's positional, and this description gets rendered as a technology.

Steps to reproduce

1. Consider this example DSL:

workspace {
  model {
    enterprise "Demo" {
      demoSystem = softwaresystem "demoSystem" {
        demoContainer = container "demoContainer" "desc" "tech" "tags" {
          component "component1" "component1 description" "component1 technology" "component1 tag1,tsg2"
          component "component2" "component2 description" "component2 technology"
          component "component3" "component3 description" 
          component "component4"
        }
      }
    }
  }
  views {
    component demoContainer {
      include *
    }
   }
}

2. Render that via Structurizr, and C4-PlantUML, eg via https://structurizr.com/dsl

3. Observe that only component3, and only in the C4-PlantUML rendering, the component3 description text appears where the technology text should. See screenshots in the next section.

Screenshot

Here's a sample show how it is correct for the Structurizr output, for all four components:

And here, you can see how for the C4-PlantUML output, component3's description appears in the technology position:

Code sample

See "Steps to reproduce" above.

Configuration

No response

Severity

Major

Priority

Low

Resolution

I'm willing to fix this myself and raise a PR

More information

Looking at the generated C4-PlantUML (for the above sample DSL), it includes:

Container_Boundary("demoSystem.demoContainer_boundary", "demoContainer", $tags="") {
  Component(demoSystem.demoContainer.component1, "component1", "component1 technology", "component1 description", $tags="")
  Component(demoSystem.demoContainer.component2, "component2", "component2 technology", "component2 description", $tags="")
  Component(demoSystem.demoContainer.component3, "component3", "component3 description", $tags="")
  Component(demoSystem.demoContainer.component4, "component4", "", $tags="")
}

You can see that for component3, then description has shifted into the technology position.

For convenience, here are links to the relevant current C4-PlantUML procedure definitions:

• Container
• ContainerDb
• ContainerQueue
• Component
• ComponentDb
• ComponentQueue

And here's the code in C4PlantUMLExporter.java that writes (sometimes incorrectly) those procedure calls (ie this is where I'd say the fixes should go):

• C4PlantUMLExporter::writeElement() - Container[Db|Queue]
• C4PlantUMLExporter::writeElement() - Component[Db|Queue]

Note, the components fix will likely conflict with my existing open PR #60, so I would strongly recommend merging that PR (assuming you're happy with it) before fixing this. Or branch off my PR.

I'd be happy to have a go at fixing this bug too. Just not sure when I'll have time to get to it.

Cheers!

[Simon Brown]

Thanks ... given that the code in the exporter explicitly does something different for null/empty technologies, I'm guessing something has recently changed with PlantUML and/or C4-PlantUML to make this invalid ... especially since nobody has raised this before. I will merge your PR, then resolve this issue.