create getTopology util

src/admin.ts

@@ -11,7 +11,7 @@ import {
 } from './operations/list_databases';
 import { executeOperation } from './operations/execute_operation';
 import { RunCommandOperation, RunCommandOptions } from './operations/run_command';
-import type { Callback } from './utils';
+import { Callback, getTopology } from './utils';
 import type { Document } from './bson';
 import type { CommandOperationOptions } from './operations/command';
 import type { Db } from './db';
@@ -80,7 +80,7 @@ export class Admin {
     options = Object.assign({ dbName: 'admin' }, options);
 
     return executeOperation(
-      this.s.db.topology,
+      getTopology(this.s.db),
       new RunCommandOperation(this.s.db, command, options),
       callback
     );
@@ -204,7 +204,7 @@ export class Admin {
     options = Object.assign({ dbName: 'admin' }, options);
 
     return executeOperation(
-      this.s.db.topology,
+      getTopology(this.s.db),
       new AddUserOperation(this.s.db, username, password, options),
       callback
     );
@@ -230,7 +230,7 @@ export class Admin {
     options = Object.assign({ dbName: 'admin' }, options);
 
     return executeOperation(
-      this.s.db.topology,
+      getTopology(this.s.db),
       new RemoveUserOperation(this.s.db, username, options),
       callback
     );
@@ -260,7 +260,7 @@ export class Admin {
     options = options || {};
 
     return executeOperation(
-      this.s.db.topology,
+      getTopology(this.s.db),
       new ValidateCollectionOperation(this, collectionName, options),
       callback
     );
@@ -284,7 +284,7 @@ export class Admin {
     options = options || {};
 
     return executeOperation(
-      this.s.db.topology,
+      getTopology(this.s.db),
       new ListDatabasesOperation(this.s.db, options),
       callback
     );

src/bulk/common.ts

@@ -8,7 +8,8 @@ import {
   hasAtomicOperators,
   Callback,
   MongoDBNamespace,
-  maxWireVersion
+  maxWireVersion,
+  getTopology
 } from '../utils';
 import { executeOperation } from '../operations/execute_operation';
 import { InsertOperation } from '../operations/insert';
@@ -908,7 +909,7 @@ export abstract class BulkOperationBase {
     // determine whether bulkOperation is ordered or unordered
     this.isOrdered = isOrdered;
 
-    const topology = collection.getTopology();
+    const topology = getTopology(collection);
     if (!topology) throw new MongoClientClosedError();
     options = options == null ? {} : options;
     // TODO Bring from driver information in isMaster

src/change_stream.ts

@@ -11,7 +11,8 @@ import {
   now,
   maybePromise,
   MongoDBNamespace,
-  Callback
+  Callback,
+  getTopology
 } from './utils';
 import type { ReadPreference } from './read_preference';
 import type { Timestamp, Document } from './bson';
@@ -221,22 +222,19 @@ export class ChangeStream extends EventEmitter {
     this.parent = parent;
     this.namespace = parent.s.namespace;
 
-    let topology: Topology | undefined;
     if (parent instanceof Collection) {
       this.type = CHANGE_DOMAIN_TYPES.COLLECTION;
-      topology = parent.getTopology();
     } else if (parent instanceof Db) {
       this.type = CHANGE_DOMAIN_TYPES.DATABASE;
-      topology = parent.topology;
     } else if (parent instanceof MongoClient) {
       this.type = CHANGE_DOMAIN_TYPES.CLUSTER;
-      topology = parent.topology;
     } else {
       throw new TypeError(
         'parent provided to ChangeStream constructor is not an instance of Collection, Db, or MongoClient'
       );
     }
 
+    const topology = getTopology(parent);
     if (!topology) throw new MongoClientClosedError();
     this.topology = topology;