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/sqlstore/migrations/ualert/alert_rule.go

@@ -171,7 +171,7 @@ func migrateAlertRuleQueries(data []alertQuery) ([]alertQuery, error) {
 	result := make([]alertQuery, 0, len(data))
 	for _, d := range data {
 		// queries that are expression are not relevant, skip them.
-		if d.DatasourceUID == expr.OldDatasourceUID {
+		if d.DatasourceUID == expr.DatasourceType {
 			result = append(result, d)
 			continue
 		}

pkg/services/sqlstore/migrations/ualert/cond_trans.go

@@ -7,6 +7,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/grafana/grafana/pkg/expr"
 	"github.com/grafana/grafana/pkg/util"
 )
 
@@ -187,7 +188,7 @@ func transConditions(set dashAlertSettings, orgID int64, dsUIDMap dsUIDLookup) (
 	ccAlertQuery := alertQuery{
 		RefID:         ccRefID,
 		Model:         exprModelJSON,
-		DatasourceUID: "-100",
+		DatasourceUID: expr.DatasourceUID,
 	}
 
 	newCond.Data = append(newCond.Data, ccAlertQuery)