fix: improve instanceof checks to support custom transformers

This commit updates two instanceof checks to instead check
the constructor name. This is done to better support custom
transformers. Because custom transformers import/require
potentially different copies of the transformer modules,
the instanceof checks do not work. This required v2 custom
transformers to rely on NODE_PATH hacks and other
workarounds.

Refs: #9362

packages/amplify-graphql-transformer-core/src/cdk-compat/file-asset.ts

@@ -20,8 +20,11 @@ export class FileAsset extends cdk.Construct implements cdk.IAsset {
     const rootStack = findRootStack(scope);
     const sythesizer = rootStack.synthesizer;
 
-    if (sythesizer instanceof TransformerStackSythesizer) {
-      sythesizer.setMappingTemplates(props.fileName, props.fileContent);
+    // Check the constructor name instead of using 'instanceof' because the latter does not work
+    // with copies of the class, which happens with custom transformers.
+    // See: https://github.com/aws-amplify/amplify-cli/issues/9362
+    if (sythesizer.constructor.name === 'TransformerStackSythesizer') {
+        (sythesizer as TransformerStackSythesizer).setMappingTemplates(props.fileName, props.fileContent);
       this.assetHash = crypto
         .createHash('sha256')
         .update(props.fileContent)

packages/amplify-graphql-transformer-core/src/transformer-context/resolver.ts

@@ -318,8 +318,11 @@ export class TransformerResolver implements TransformerResolverProvider {
   };
 
   private substitueSlotInfo(template: MappingTemplateProvider, slotName: string, index: number) {
-    if (template instanceof S3MappingTemplate) {
-      template.substitueValues({ slotName, slotIndex: index, typeName: this.typeName, fieldName: this.fieldName });
+    // Check the constructor name instead of using 'instanceof' because the latter does not work
+    // with copies of the class, which happens with custom transformers.
+    // See: https://github.com/aws-amplify/amplify-cli/issues/9362
+    if (template.constructor.name === 'S3MappingTemplate') {
+      (template as S3MappingTemplate).substitueValues({ slotName, slotIndex: index, typeName: this.typeName, fieldName: this.fieldName });
     }
   }