correct the err message

Author: bhshkh

firestore/pipeline_integration_test.go

@@ -931,9 +931,6 @@ func aggregationFuncs(t *testing.T) {
 		docRefs = append(docRefs, docRef)
 		h.mustCreate(docRef, d)
 	}
-	t.Cleanup(func() {
-		deleteDocuments(docRefs)
-	})
 
 	pipeline := client.Pipeline().Collection(coll.ID).
 		Sort(Orders(Ascending(FieldOf("val")))).

firestore/pipeline_source.go

@@ -14,6 +14,8 @@
 
 package firestore
 
+import "fmt"
+
 // PipelineSource is a factory for creating Pipeline instances.
 // It is obtained by calling [Client.Pipeline].
 //
@@ -168,7 +170,14 @@ func (ps *PipelineSource) Documents(refs []*DocumentRef, opts ...DocumentsOption
 			opt.applyStage(options)
 		}
 	}
-	return newPipeline(ps.client, newInputStageDocuments(refs, options))
+	p := newPipeline(ps.client, newInputStageDocuments(refs, options))
+	for _, ref := range refs {
+		if ref == nil {
+			p.err = fmt.Errorf("firestore: Documents() cannot contain nil references")
+			break
+		}
+	}
+	return p
 }
 
 // CreateFromQuery creates a new [Pipeline] from the given [Queryer]. Under the hood, this will

firestore/pipeline_stage.go

@@ -158,7 +158,7 @@ func (s *inputStageDocuments) toProto() (*pb.Pipeline_Stage, error) {
 	args := make([]*pb.Value, len(s.refs))
 	for i, ref := range s.refs {
 		if ref == nil {
-			return nil, fmt.Errorf("firestore: internal error: inputStageDocuments contains nil reference")
+			return nil, fmt.Errorf("firestore: inputStageDocuments contains nil reference")
 		}
 		args[i] = &pb.Value{ValueType: &pb.Value_ReferenceValue{ReferenceValue: "/" + ref.shortPath}}
 	}