Expressions: Fixes the issue showing expressions editor (#62510)

* Use suggested value for uid

* update the snapshot

* use __expr__

* replace all -100 with __expr__

* update snapshot

* more changes

* revert redundant change

* Use expr.DatasourceUID where it's possible

* generate files

pkg/services/ngalert/models/alert_query.go

@@ -88,7 +88,7 @@ type AlertQuery struct {
 	// RelativeTimeRange is the relative Start and End of the query as sent by the frontend.
 	RelativeTimeRange RelativeTimeRange `json:"relativeTimeRange"`
 
-	// Grafana data source unique identifier; it should be '-100' for a Server Side Expression operation.
+	// Grafana data source unique identifier; it should be '__expr__' for a Server Side Expression operation.
 	DatasourceUID string `json:"datasourceUid"`
 
 	// JSON is the raw JSON query and includes the above properties as well as custom properties.

pkg/services/ngalert/models/alert_query_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/grafana/grafana/pkg/expr"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -29,7 +30,7 @@ func TestAlertQuery(t *testing.T) {
 					"queryType": "metricQuery",
 					"extraParam": "some text"
 				}`),
-				DatasourceUID: "-100",
+				DatasourceUID: expr.DatasourceUID,
 			},
 			expectedIsExpression: true,
 			expectedMaxPoints:    int64(defaultMaxDataPoints),

pkg/services/ngalert/models/testing.go

@@ -300,7 +300,7 @@ func CreateClassicConditionExpression(refID string, inputRefID string, reducer s
 	return AlertQuery{
 		RefID:         refID,
 		QueryType:     expr.DatasourceType,
-		DatasourceUID: expr.OldDatasourceUID,
+		DatasourceUID: expr.DatasourceUID,
 		// the format corresponds to model `ClassicConditionJSON` in /pkg/expr/classic/classic.go
 		Model: json.RawMessage(fmt.Sprintf(`
 		{
@@ -334,7 +334,7 @@ func CreateClassicConditionExpression(refID string, inputRefID string, reducer s
                     }
                 }
             ]
-		}`, refID, inputRefID, operation, threshold, reducer, expr.OldDatasourceUID, expr.DatasourceType)),
+		}`, refID, inputRefID, operation, threshold, reducer, expr.DatasourceUID, expr.DatasourceType)),
 	}
 }