feat: Add template functions for proper YAML escaping and quoting

cmd/promster/main.go

@@ -2,14 +2,15 @@ package main
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"go.lumeweb.com/etcd-registry/types"
-	"sort"
 	"io"
 	"net/http"
 	"os"
 	"os/signal"
 	"reflect"
+	"sort"
 	"strings"
 	"sync"
 	"text/template"
@@ -67,6 +68,16 @@ func (sg *ServiceGroup) Validate() error {
 	return nil
 }
 
+var templateFuncs = template.FuncMap{
+	"quote": func(v interface{}) string {
+		return fmt.Sprintf("%q", v)
+	},
+	"toJson": func(v interface{}) string {
+		b, _ := json.Marshal(v)
+		return string(b)
+	},
+}
+
 func executeTemplate(data interface{}) (string, error) {
 	// Validate service groups before template execution
 	config, ok := data.(PrometheusConfig)
@@ -77,7 +88,7 @@ func executeTemplate(data interface{}) (string, error) {
 			}
 		}
 	}
-	tmpl, err := template.New(PROM_TEMPLATE_FILE).Parse(prometheusTemplate)
+	tmpl, err := template.New(PROM_TEMPLATE_FILE).Funcs(templateFuncs).Parse(prometheusTemplate)
 	if err != nil {
 		return "", err
 	}

cmd/promster/prometheus.yml.tmpl

@@ -9,27 +9,27 @@ scrape_configs:
       - targets: ['localhost:9090']
     {{ if .AdminPassword }}
     basic_auth:
-      username: "{{.AdminUsername}}"
-      password: "{{.AdminPassword}}"
+      username: {{.AdminUsername | quote}}
+      password: {{.AdminPassword | quote}}
     {{ end }}
 
   {{- if .ServiceGroups }}
   {{- range .ServiceGroups }}
-  - job_name: '{{ .Name }}'
-    scheme: "{{$.Scheme}}"
+  - job_name: {{.Name | quote}}
+    scheme: {{$.Scheme | quote}}
     tls_config:
       insecure_skip_verify: {{if eq $.TlsInsecure "true"}}true{{else}}false{{end}}
     static_configs:
-      - targets: {{ .Targets }}
+      - targets: {{.Targets | toJson}}
         labels:
           {{- range $key, $value := .Labels }}
-          {{ $key }}: "{{ $value }}"
+          {{$key}}: {{$value | quote}}
           {{- end }}
     {{ if .BasicAuth }}
     basic_auth:
-      username: "{{ .BasicAuth.Username }}"
-      password: "{{ .BasicAuth.Password }}"
+      username: {{.BasicAuth.Username | quote}}
+      password: {{.BasicAuth.Password | quote}}
     {{ end }}
-    metrics_path: "{{ .MetricsPath }}"
+    metrics_path: {{.MetricsPath | quote}}
   {{- end }}
   {{- end }}