def "one node changed"() {
        def document = TestUtil.parseQuery("{foo}")

        AstTransformer astTransformer = new AstTransformer()

        def visitor = new NodeVisitorStub() {

            @Override
            TraversalControl visitField(Field node, TraverserContext<Node> context) {
                Field changedField = node.transform({ builder -> builder.name("foo2") })
                return TreeTransformerUtil.changeNode(context, changedField)
            }
        }


        when:
        def newDocument = astTransformer.transform(document, visitor)

        then:
        printAstCompact(newDocument) == "{foo2}"

    }

from graphql.language.AstTransformerTest

The trick is to use a AST transformer and also to return via the graphql.util.TreeTransformerUtil#changeNode method.

Is not intuitive since there is a changeNode on the context but it does not deep change things. Rather you need to use TreeTransformerUtil.changeNode.

Thank you @bbakerman. I just also decided to check out the tests and also figured it out. I think I will do a PR and add some documentation to help others avode the hours of time spent trying to get it to work while using the wrong method.

Yeah it is tricky. I am not sure what the changeNode on traversal context does honestly. I never wrote any of this code.

@andimarek knows more

We do have https://www.graphql-java.com/documentation/schema#changing-schema - which is about changing schema but its the same generic visitor code mechanisms.

If you'd like to help out with any documentation, our documentation repo is https://github.com/graphql-java/graphql-java-page and you're welcome to open a pull request

I will take a look and see what I can contribute. Thanks.