Alerting: Evaluate data templating in alert rule name and message (#29908)

* evaluate Go style template

* inlince func

* add test case

* PR feedback and add tests for templte data map func

* Add test case

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>

* do regex check

* ensure ecape

* small cleanup

* dont exit on template execution errors

* add info tooltip

* add docs

* switch from go tmpl to regex

* update docs/comments

* update tooltip wording

* update docs wording

* add simple test

* avoid .MustCompile

* point to labels in docs

* update docs

* fix docs links

* remove line

* fix lint

* add note about multiple labels

* propagate labels for CM

* update docs

* remove whitespace

* update task title

* update docs

* pr feedback

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/services/alerting/eval_context.go

@@ -3,6 +3,7 @@ package alerting
 import (
 	"context"
 	"fmt"
+	"regexp"
 	"time"
 
 	"github.com/grafana/grafana/pkg/bus"
@@ -178,3 +179,66 @@ func getNewStateInternal(c *EvalContext) models.AlertStateType {
 
 	return models.AlertStateOK
 }
+
+// evaluateNotificationTemplateFields will treat the alert evaluation rule's name and message fields as
+// templates, and evaluate the templates using data from the alert evaluation's tags
+func (c *EvalContext) evaluateNotificationTemplateFields() error {
+	if len(c.EvalMatches) < 1 {
+		return nil
+	}
+
+	templateDataMap, err := buildTemplateDataMap(c.EvalMatches)
+	if err != nil {
+		return err
+	}
+
+	ruleMsg, err := evaluateTemplate(c.Rule.Message, templateDataMap)
+	if err != nil {
+		return err
+	}
+	c.Rule.Message = ruleMsg
+
+	ruleName, err := evaluateTemplate(c.Rule.Name, templateDataMap)
+	if err != nil {
+		return err
+	}
+	c.Rule.Name = ruleName
+
+	return nil
+}
+
+func evaluateTemplate(s string, m map[string]string) (string, error) {
+	for k, v := range m {
+		re, err := regexp.Compile(fmt.Sprintf(`\${%s}`, regexp.QuoteMeta(k)))
+		if err != nil {
+			return "", err
+		}
+		s = re.ReplaceAllString(s, v)
+	}
+
+	return s, nil
+}
+
+// buildTemplateDataMap builds a map of alert evaluation tag names to a set of associated values (comma separated)
+func buildTemplateDataMap(evalMatches []*EvalMatch) (map[string]string, error) {
+	var result = map[string]string{}
+	for _, match := range evalMatches {
+		for tagName, tagValue := range match.Tags {
+			// skip duplicate values
+			rVal, err := regexp.Compile(fmt.Sprintf(`\b%s\b`, regexp.QuoteMeta(tagValue)))
+			if err != nil {
+				return nil, err
+			}
+			rMatch := rVal.FindString(result[tagName])
+			if len(rMatch) > 0 {
+				continue
+			}
+			if _, exists := result[tagName]; exists {
+				result[tagName] = fmt.Sprintf("%s, %s", result[tagName], tagValue)
+			} else {
+				result[tagName] = tagValue
+			}
+		}
+	}
+	return result, nil
+}