Jinja

[vadim-zabolotniy]

Consider replacement of current template engine(Pystache/Chevron) by Jinja. Requirements:

• [x] {{ }} - template variable markers.
• [x] Getting list item by numeric index(need for case with IP in service ingress).
• [x] Skipping of invalid variable placeholder error(need on 1st render when application Kubernetes entities wasn't created yet).
• [x] Error rising when variable placeholder is invalid(need on 2nd render when application successfully deployed and context is complete).
• [ ] Optional Keep template variable place holder if it can't be found in context.

[vadim-zabolotniy]

Found issues:

• Jinja cant work with dashes in variables names. {{components.redis.manifest.Service.redis-master.status.loadBalancer.ingress.0.ip}} here redis-master causes error. As workaround we can specify such keys in quotes(' or ") Service["redis-master"]. This is because Jinja applies to variables same rules as Python to own variables.

Notes:

• To rise error when template variable is absent pass jinja2.StrictUndefined policy to jinja2.Template initializer, e.g. template = jinja2.Template('template', undefined=jinja2.StrictUndefined)