charts: bypass unqouted Jinja dump to YAML

This hack is required to bypass the fact that dumping Jinja
to YAML does not work with the render script because of the presence
of unquote special characters e.g `{%`.

If we try to escape thess special characters, we end up with type(str)
always and in some special conditions, we need for example replicas count
to be of type(int)

charts/prometheus-operator.yaml

@@ -9,7 +9,7 @@ commonLabels:
 alertmanager:
   alertmanagerSpec:
     image:
-      repository: '''{%- endraw -%}{{ build_image_name("alertmanager", False) }}{%- raw -%}'''
+      repository: '__image__(alertmanager)'
 
     nodeSelector:
       node-role.kubernetes.io/infra: ''
@@ -24,6 +24,8 @@ alertmanager:
         operator: 'Exists'
         effect: 'NoSchedule'
 
+    replicas: '__var__(alertmanager.spec.deployment.replicas)'
+
     storage:
       volumeClaimTemplate:
         spec:
@@ -56,22 +58,22 @@ prometheusOperator:
       effect: 'NoSchedule'
 
   image:
-    repository: '{%- endraw -%}{{ build_image_name(\"prometheus-operator\", False) }}{%- raw -%}'
+    repository: '__image__(prometheus-operator)'
 
   configmapReloadImage:
-    repository: '{%- endraw -%}{{ build_image_name("configmap-reload", False) }}{%- raw -%}'
+    repository: '__image__(configmap-reload)'
 
   prometheusConfigReloaderImage:
-    repository: '{%- endraw -%}{{ build_image_name("prometheus-config-reloader", False) }}{%- raw -%}'
+    repository: '__image__(prometheus-config-reloader)'
 
   hyperkubeImage:
-    repository: '''{%- endraw -%}{{ build_image_name("hyperkube", False) }}{%- raw -%}'''
+    repository: '__image__(hyperkube)'
 
 
 prometheus:
   prometheusSpec:
     image:
-      repository: '''{%- endraw -%}{{ build_image_name("prometheus", False) }}{%- raw -%}'''
+      repository: '__image__(prometheus)'
 
     tolerations:
       - key: 'node-role.kubernetes.io/bootstrap'
@@ -81,6 +83,8 @@ prometheus:
         operator: 'Exists'
         effect: 'NoSchedule'
 
+    replicas: '__var__(prometheus.spec.deployment.replicas)'
+
     nodeSelector:
       node-role.kubernetes.io/infra: ''
 
@@ -102,10 +106,10 @@ grafana:
   adminPassword: admin
 
   image:
-    repository: '{%- endraw -%}{{ build_image_name(\"grafana\", False) }}{%- raw -%}'
+    repository: '__image__(grafana)'
 
   sidecar:
-    image: '{%- endraw -%}{{ build_image_name(\"k8s-sidecar\", False) }}{%- raw -%}:0.1.20'
+    image: '__image__(k8s-sidecar):0.1.20'
 
   nodeSelector:
     node-role.kubernetes.io/infra: ''
@@ -118,6 +122,9 @@ grafana:
       operator: 'Exists'
       effect: 'NoSchedule'
 
+  replicas: '__var__(grafana.spec.deployment.replicas)'
+
+
   ingress:
     enabled: true
     annotations:
@@ -140,7 +147,7 @@ grafana:
 
 kube-state-metrics:
   image:
-    repository: '{%- endraw -%}{{ build_image_name(\"kube-state-metrics\", False) }}{%- raw -%}'
+    repository: '__image__(kube-state-metrics)'
 
   nodeSelector:
     node-role.kubernetes.io/infra: ''
@@ -156,7 +163,7 @@ kube-state-metrics:
 
 prometheus-node-exporter:
   image:
-    repository: '{%- endraw -%}{{ build_image_name(\"node-exporter\", False) }}{%- raw -%}'
+    repository: '__image__(node-exporter)'
 
 
 kubeEtcd:

charts/render.py

@@ -16,9 +16,18 @@
   `app.kubernetes.io/managed-by` to `salt`, and copy any `app` and
   `component` fields to the canonical `app.kubernetes.io/name` and
   `app.kubernetes.io/component` fields
+- Replace YAML-safe special strings (used in Helm values definitions) with the
+  appropriate Jinja syntax. Supports:
+    - "__var__(<varname>)", to replace with "{{ <varname> }}" (useful when
+      retrieving variables from service configuration ConfigMaps)
+    - "__image__(<imgname>)", to replace with
+      "{{ build_image_name("<imgname>", False) }}"
+    - "__full_image__(<imgname>)", to replace with
+      "{{ build_image_name("<imgname>") }}"
 '''
 
 import argparse
+import io
 import re
 import sys
 import subprocess
@@ -28,18 +37,18 @@
 from yaml.representer import SafeRepresenter
 
 
-START_BLOCK = '''
+START_BLOCK = """
 #!jinja | metalk8s_kubernetes
-{{%- from "metalk8s/repo/macro.sls" import build_image_name with context %}}
 
+{{%- from "metalk8s/repo/macro.sls" import build_image_name with context %}}
 {configlines}
 
 {{% raw %}}
-'''
+"""
 
-END_BLOCK = '''
+END_BLOCK = """
 {% endraw %}
-'''
+"""
 
 
 def fixup_metadata(namespace, doc):
@@ -117,6 +126,31 @@ def keep_doc(doc):
     return True
 
 
+def replace_magic_strings(rendered_yaml):
+    # Handle __var__
+    result = re.sub(
+        r'__var__\((?P<varname>[\w\-_]+(?:\.[\w\-_]+)*)\)',
+        r'{% endraw -%}{{ \g<varname> }}{%- raw %}',
+        rendered_yaml,
+    )
+
+    # Handle __image__
+    result = re.sub(
+        r'__image__\((?P<imgname>[\w\-]+)\)',
+        r'{% endraw -%}{{ build_image_name("\g<imgname>", False) }}{%- raw %}',
+        result,
+    )
+
+    # Handle __full_image__ (include version tag in the rendered name)
+    result = re.sub(
+        r'__full_image__\((?P<imgname>[\w\-]+)\)',
+        r'{% endraw -%}{{ build_image_name("\g<imgname>") }}{%- raw %}',
+        result,
+    )
+
+    return result
+
+
 def main():
     parser = argparse.ArgumentParser()
     parser.add_argument('name', help="Denotes the name of the chart")
@@ -175,13 +209,17 @@ def main():
     )
     sys.stdout.write('\n')
 
+    stream = io.StringIO()
     yaml.safe_dump_all(
         (fixup(doc)
             for doc in yaml.safe_load_all(template)
             if keep_doc(doc)),
-        sys.stdout,
+        stream,
         default_flow_style=False,
     )
+    stream.seek(0)
+
+    sys.stdout.write(replace_magic_strings(stream.read()))
 
     sys.stdout.write(END_BLOCK)