@lyrixx I have just checked and I think your .puml result is not syntactically valid.

state "a" <<initial>> 
state "b"
"a" --> "b": "t1"

=> That is not valid, you have a Syntax Error
Instead PlantUML as this concept of aliases

state "a" as a<<initial>> 
state "b" as b
a --> b: "t1"

Let me push the valid test fixtures for you to update the dumper accordingly :)

Finally, there is a simpler way, just add allow_mixing in the header everywhere. Look at the fixtures inside the "square" folder.
Plus remove the if here: https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Workflow/Dumper/PlantUmlDumper.php#L118

cc @lyrixx thx!

Thanks @Plopix for the review.

I have testes in real life with really strange char and my code works.
My test was base on this workflow:

        weird:
            type: workflow
            supports: stdClass # Just a hack
            places:
                - "a'"
                - 'é!'
                - 'b\"(\"'
            transitions:
                -
                    name: '{}'
                    from: "a'"
                    to: 'é!'

And as it's already a workflow, the allow_mixing was already present.
If I remove the " in the pum dump, then it's broken.

Here is the dump

@startuml
allow_mixing
title weird
skinparam titleBorderRoundCorner 15
skinparam titleBorderThickness 2
skinparam state {
    BackgroundColor<<initial>> #87b741
    BackgroundColor<<marked>> #3887C6
    BorderColor #3887C6
    BorderColor<<marked>> Black
    FontColor<<marked>> White
}
skinparam agent {
    BackgroundColor #ffffff
    BorderColor #3887C6
}
state "a'" <<initial>>
state "é!"
state "b\(\"
agent "{}"
"a'" --> "{}"
"{}" --> "é!"
@enduml

**But** You are right about the "state_machine dumper". We should always add `allow_mixing`.
I have updated the PR.

Not really related question: Do you really use the nofooter option of the dumper? (right now, there are not way to use it without writing / editing some code) I no-one use it, I would like to remove it (less code === less bug)

Yes indeed the allow_mixing is enough and was present in the workflow dump. I just picked one file randomly in your PR that is how I saw that syntax error and testing a workflow I saw it was working then I figured the allow_mixing.

Ok to remove nofooter I agree with the less code less bug. (having the footer was prob too fancy)

We should always add allow_mixing. I have updated the PR.

I don't see the changes but I could have a look when done!
thx!

I don't see the changes but I could have a look when done!

Indeed, I forgot to push ;) It's not pushed