feat: improve variable handling

[andaryjo]

@lukasjarosch These changes do not seem to resolve the problem we discussed. Trying to reference a class that goes by the same name as the yaml key still throws the same error, just less helpful this time 😄

Previous:

jandary@mbp doratheexplorer % go run main.go
reference to invalid variable '${flags:sandbox}': unexpected node type string at index 1

With skipper on feat/improve-template-undefined-value-handling:

jandary@mbp doratheexplorer % go run main.go
unexpected node type string at index 1

[andaryjo]

My bad, on the second try it somehow worked:

jandary@mbp doratheexplorer % go run main.go
recursive variable usage found at path 'features': ${features:sandbox}

[andaryjo]

Demo setup of what I'm trying to achieve here: https://github.com/andaryjo/doratheexplorer/tree/0805d9f440cbbd06a0c20158cad2a2c13449cd5e

[lukasjarosch]

I'd love to see the demo setup, but the Repo seems to be private 😄

[lukasjarosch]

I have reviewed your demo and it did indeed not behave as expected. The recursion detection was not working properly. I've now improved the error messages and fixed up the recursion detection.

With your example you should now receive:

cannot load target data for variable ${features:sandbox}: GetPath: undefined path: [features sandbox]

This is now indeed what a user would expect at this point, don't you think?