provisioner: add json template function

This change adds `json` function that enables use of
json-formatted strings in templates.

This could be used to define structured configuration values or
repeated chunks in templates that require modification of several values,
see provisiner/testdata/json.template.yaml for and example use.

Signed-off-by: Alexander Yastrebov <[email protected]>

provisioner/template.go

@@ -6,6 +6,7 @@ import (
 	"crypto/x509"
 	"encoding/base64"
 	"encoding/binary"
+	"encoding/json"
 	"encoding/pem"
 	"errors"
 	"fmt"
@@ -113,6 +114,7 @@ func renderTemplate(context *templateContext, file string) (string, error) {
 		"azID":                 azID,
 		"azCount":              azCount,
 		"split":                split,
+		"json":                 parseJson,
 		"mountUnitName":        mountUnitName,
 		"accountID":            accountID,
 		"portRanges":           portRanges,
@@ -294,6 +296,11 @@ func accountID(account string) (string, error) {
 	return items[1], nil
 }
 
+func parseJson(input string) (result interface{}, err error) {
+	err = json.Unmarshal([]byte(input), &result)
+	return
+}
+
 type HostPort struct {
 	Host string
 	Port string

provisioner/template_test.go

@@ -2,6 +2,7 @@ package provisioner
 
 import (
 	"fmt"
+	"os"
 	"strconv"
 	"testing"
 
@@ -1164,3 +1165,51 @@ func TestNodePoolGroupsProfile(t *testing.T) {
 		})
 	}
 }
+
+func TestJson(t *testing.T) {
+	t.Run("object", func(t *testing.T) {
+		result, err := renderSingle(
+			t,
+			`{{ with json .Values.data }}name={{ .name }} value={{ .value }}{{end}}`,
+			`{"name": "foo", "value": "bar"}`)
+
+		require.NoError(t, err)
+		require.Equal(t, "name=foo value=bar", result)
+	})
+
+	t.Run("range over array", func(t *testing.T) {
+		result, err := renderSingle(
+			t,
+			`{{ range json .Values.data }}{{ .name }}={{ .value }} {{end}}`,
+			`[{"name": "foo", "value": "bar"}, {"name": "baz", "value": "qux"}]`)
+
+		require.NoError(t, err)
+		require.Equal(t, "foo=bar baz=qux ", result)
+	})
+
+	t.Run("range over object", func(t *testing.T) {
+		result, err := renderSingle(
+			t,
+			`{{ range $key, $value := json .Values.data }}{{ $key }}={{ $value }} {{end}}`,
+			`{"name": "foo", "value": "bar"}`)
+
+		require.NoError(t, err)
+		require.Equal(t, "name=foo value=bar ", result)
+	})
+
+	t.Run("example manifest", func(t *testing.T) {
+		template, err := os.ReadFile("testdata/json.template.yaml")
+		require.NoError(t, err)
+
+		expected, err := os.ReadFile("testdata/json.expected.yaml")
+		require.NoError(t, err)
+
+		result, err := renderSingle(
+			t,
+			string(template),
+			"")
+
+		require.NoError(t, err)
+		require.Equal(t, string(expected), result)
+	})
+}

provisioner/testdata/json.expected.yaml

@@ -0,0 +1,37 @@
+
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: "stable"
+  namespace: kube-system
+  labels:
+    application: app
+    version: "v1"
+spec:
+
+  selector:
+    matchLabels:
+      deployment: "stable"
+  template: |
+    omitted for clarity
+
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: "alpha"
+  namespace: kube-system
+  labels:
+    application: app
+    version: "v2"
+spec:
+
+  replicas: 1
+
+  selector:
+    matchLabels:
+      deployment: "alpha"
+  template: |
+    omitted for clarity
+

provisioner/testdata/json.template.yaml

@@ -0,0 +1,23 @@
+{{ range json `[
+  {"name": "stable", "version": "v1"},
+  {"name": "alpha", "version": "v2", "replicas": 1}
+]` }}
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: "{{ .name }}"
+  namespace: kube-system
+  labels:
+    application: app
+    version: "{{ .version }}"
+spec:
+{{ if index . "replicas" }}
+  replicas: {{ .replicas }}
+{{ end }}
+  selector:
+    matchLabels:
+      deployment: "{{ .name }}"
+  template: |
+    omitted for clarity
+{{ end }}