Alerting: Display query from grafana-managed alert rules on /api/v1/rules (#45969)

* Aleting: Extract query from alerting rule model for api/v1/rules

* more changes and fixtures

* appease the linter

pkg/services/ngalert/models/alert_query.go

@@ -2,6 +2,7 @@ package models
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"time"
 
@@ -12,6 +13,8 @@ import (
 const defaultMaxDataPoints float64 = 43200 // 12 hours at 1sec interval
 const defaultIntervalMS float64 = 1000
 
+var ErrNoQuery = errors.New("no `expr` property in the query model")
+
 // Duration is a type used for marshalling durations.
 type Duration time.Duration
 
@@ -174,6 +177,28 @@ func (aq *AlertQuery) GetDatasource() (string, error) {
 	return aq.DatasourceUID, nil
 }
 
+// GetQuery returns the query defined by `expr` within the model.
+// Returns an ErrNoQuery if it is unable to find the query.
+// Returns an error if it is not able to cast the query to a string.
+func (aq *AlertQuery) GetQuery() (string, error) {
+	if aq.modelProps == nil {
+		err := aq.setModelProps()
+		if err != nil {
+			return "", err
+		}
+	}
+	query, ok := aq.modelProps["expr"]
+	if !ok {
+		return "", ErrNoQuery
+	}
+
+	q, ok := query.(string)
+	if !ok {
+		return "", fmt.Errorf("failed to cast query to string: %v", aq.modelProps["expr"])
+	}
+	return q, nil
+}
+
 func (aq *AlertQuery) GetModel() ([]byte, error) {
 	err := aq.setMaxDatapoints()
 	if err != nil {

pkg/services/ngalert/models/alert_query_test.go

@@ -2,6 +2,7 @@ package models
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"testing"
 	"time"
@@ -110,7 +111,7 @@ func TestAlertQuery(t *testing.T) {
 				Model: json.RawMessage(`{
 					"queryType": "metricQuery",
 					"intervalMs": "invalid",
-					"extraParam": "some text"	
+					"extraParam": "some text"
 				}`),
 			},
 			expectedIsExpression: false,
@@ -245,3 +246,38 @@ func TestAlertQueryMarshalling(t *testing.T) {
 		}
 	}
 }
+
+func TestAlertQuery_GetQuery(t *testing.T) {
+	tc := []struct {
+		name       string
+		alertQuery AlertQuery
+		expected   string
+		err        error
+	}{
+		{
+			name:       "when a query is present",
+			alertQuery: AlertQuery{Model: json.RawMessage(`{"expr": "sum by (job) (up)"}`)},
+			expected:   "sum by (job) (up)",
+		},
+		{
+			name:       "when no query is found",
+			alertQuery: AlertQuery{Model: json.RawMessage(`{"exprisnot": "sum by (job) (up)"}`)},
+			err:        ErrNoQuery,
+		},
+		{
+			name:       "when we're unable to cast the query to a string",
+			alertQuery: AlertQuery{Model: json.RawMessage(`{"expr": {"key": 1}}`)},
+			err:        errors.New("failed to cast query to string: map[key:1]"),
+		},
+	}
+
+	for _, tt := range tc {
+		t.Run(tt.name, func(t *testing.T) {
+			expected, err := tt.alertQuery.GetQuery()
+			if err != nil {
+				require.Equal(t, tt.err, err)
+			}
+			require.Equal(t, tt.expected, expected)
+		})
+	}
+}