Transform a stream of YAML documents

old-docs.yamldata

---
field1: red1
field2:
  field2a: red 2.a
  filed2b: red 2.b
field3:
- red 3.a
- red 3.b
---
field1: green1
field2:
  field2a: green 2.a
  filed2b: green 2.b
field3:
- green 3.a
- green 3.b
---
field1: blue1
field2:
  field2a: blue 2.a
  filed2b: blue 2.b
field3:
- blue 3.a
- blue 3.b

transform.yaml

#@ load("@ytt:yaml", "yaml")
#@ load("@ytt:data", "data")

#@ def transform(old):
apiVersion: v1alpha1
kind: NewHotness
metadata:
  name: #@ old["field1"]
  annotations: #@ old["field2"]
spec:
  containers:
  #@ for app in old["field3"]:
  - name: #@ app
    image: #@ "{}:latest".format(app)
  #@ end
#@ end

#@ old_docs_data = data.read("old-docs.yamldata").split("\n---\n")

#@ for doc_data in old_docs_data:
#@   if doc_data == "": continue
--- #@ transform(yaml.decode(doc_data))
#@ end