refactor: support transaction concerns in aggregation operation

Author: mbroadst

lib/operations/aggregate_operation.js

@@ -12,6 +12,8 @@ const MIN_WIRE_VERSION_$OUT_READ_CONCERN_SUPPORT = 8;
 
 class AggregateOperation extends CommandOperationV2 {
   constructor(parent, pipeline, options) {
+    // ensure we receive an unchanged raw response from the server (for cursor logic)
+    options.full = true;
     super(parent, options);
 
     this.target =
@@ -41,9 +43,14 @@ class AggregateOperation extends CommandOperationV2 {
   execute(server, callback) {
     const options = this.options;
     const serverWireVersion = maxWireVersion(server);
+    const inTransaction = this.session && this.session.inTransaction();
 
     const command = { aggregate: this.target, pipeline: this.pipeline };
-    if (!this.hasWriteStage || serverWireVersion >= MIN_WIRE_VERSION_$OUT_READ_CONCERN_SUPPORT) {
+
+    if (
+      (!this.hasWriteStage || serverWireVersion >= MIN_WIRE_VERSION_$OUT_READ_CONCERN_SUPPORT) &&
+      !inTransaction
+    ) {
       Object.assign(command, { readConcern: this.readConcern });
     }