Panic if rule type was not expected

Signed-off-by: Danny Kopping <danny.kopping@grafana.com>

rules/origin.go

@@ -15,6 +15,7 @@ package rules
 
 import (
 	"context"
+	"fmt"
 
 	"github.com/prometheus/prometheus/model/labels"
 )
@@ -43,7 +44,7 @@ func NewRuleDetail(r Rule) RuleDetail {
 	case *RecordingRule:
 		kind = KindRecording
 	default:
-		kind = "unknown"
+		panic(fmt.Sprintf(`unknown rule type "%T"`, r))
 	}
 
 	return RuleDetail{

rules/origin_test.go

@@ -0,0 +1,37 @@
+package rules
+
+import (
+	"context"
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/prometheus/prometheus/model/labels"
+	"github.com/prometheus/prometheus/promql"
+	"github.com/prometheus/prometheus/promql/parser"
+	"github.com/stretchr/testify/require"
+)
+
+type unknownRule struct{}
+
+func (u unknownRule) Name() string          { return "" }
+func (u unknownRule) Labels() labels.Labels { return nil }
+func (u unknownRule) Eval(ctx context.Context, time time.Time, queryFunc QueryFunc, url *url.URL, i int) (promql.Vector, error) {
+	return nil, nil
+}
+func (u unknownRule) String() string                               { return "" }
+func (u unknownRule) Query() parser.Expr                           { return nil }
+func (u unknownRule) SetLastError(err error)                       {}
+func (u unknownRule) LastError() error                             { return nil }
+func (u unknownRule) SetHealth(health RuleHealth)                  {}
+func (u unknownRule) Health() RuleHealth                           { return "" }
+func (u unknownRule) SetEvaluationDuration(duration time.Duration) {}
+func (u unknownRule) GetEvaluationDuration() time.Duration         { return 0 }
+func (u unknownRule) SetEvaluationTimestamp(time time.Time)        {}
+func (u unknownRule) GetEvaluationTimestamp() time.Time            { return time.Time{} }
+
+func TestNewRuleDetailPanics(t *testing.T) {
+	require.PanicsWithValue(t, `unknown rule type "rules.unknownRule"`, func() {
+		NewRuleDetail(unknownRule{})
+	})
+}