In certain cases, it is possible to generate invalid Jenkinsfiles.

For one thing, we need to escape backslashes.

Additionally, I suggest during the JSON validation, we convert to declarative, and then also validate the declarative file, just to prevent invalid files from ever being created, since we can't actually load them into the editor again.

An example JSON request that generates invalid declarative:

{"pipeline":{"agent":{"type":"any"},"stages":[{"name":"Build","branches":[{"name":"default","steps":[{"name":"sh","arguments":[{"key":"script","value":{"isLiteral":true,"value":"echo 'hello\\'"}}]}]}]}]}}