refactor: centralize DynamoDB GSI accessor into a shared helper

Dedupe the aws-cdk-lib 2.252/2.260 _globalSecondaryIndexes fallback across 3
packages; no behavior change [follow-up to #3505]

Extracts the dual-path accessor `table['_globalSecondaryIndexes'] ??
table.globalSecondaryIndexes` into a single exported helper
`getGlobalSecondaryIndexes` in @aws-amplify/graphql-transformer-core and points
all three call sites at it (relational-transformer resolvers, transformer-core
schema-utils getKeySchema, conversation-transformer resolver generator).
Identical dual-path semantics preserved.

Author: Simone319

packages/amplify-graphql-conversation-transformer/src/transformer-steps/conversation-resolver-generator.ts

@@ -1,6 +1,11 @@
 import { conversation } from '@aws-amplify/ai-constructs';
 import { overrideIndexAtCfnLevel } from '@aws-amplify/graphql-index-transformer';
-import { getModelDataSourceNameForTypeName, getTable, TransformerResolver } from '@aws-amplify/graphql-transformer-core';
+import {
+  getModelDataSourceNameForTypeName,
+  getGlobalSecondaryIndexes,
+  getTable,
+  TransformerResolver,
+} from '@aws-amplify/graphql-transformer-core';
 import { DataSourceProvider, TransformerContextProvider } from '@aws-amplify/graphql-transformer-interfaces';
 import { BackendOutputEntry, BackendOutputStorageStrategy } from '@aws-amplify/plugin-types';
 import * as cdk from 'aws-cdk-lib';
@@ -331,10 +336,7 @@ export class ConversationResolverGenerator {
       writeCapacity: cdk.Fn.ref(ResourceConstants.PARAMETERS.DynamoDBModelTableWriteIOPS),
     });
 
-    // aws-cdk-lib 2.260 renamed the private `globalSecondaryIndexes` array on the DynamoDB L2 `Table` to
-    // `_globalSecondaryIndexes` (an `ArrayBox` exposing the same `find` surface and `{ indexName, keySchema }`
-    // element shape); Amplify's managed-table construct keeps the public `globalSecondaryIndexes` array.
-    const globalSecondaryIndexes = table['_globalSecondaryIndexes'] ?? table.globalSecondaryIndexes;
+    const globalSecondaryIndexes = getGlobalSecondaryIndexes(table);
     const gsi = globalSecondaryIndexes.find((g: any) => g.indexName === indexName);
 
     const newIndex = {

packages/amplify-graphql-relational-transformer/src/resolvers.ts

@@ -1,6 +1,6 @@
 import { attributeTypeFromType, overrideIndexAtCfnLevel } from '@aws-amplify/graphql-index-transformer';
 import { generateApplyDefaultsToInputTemplate } from '@aws-amplify/graphql-model-transformer';
-import { InvalidDirectiveError, MappingTemplate, getTable } from '@aws-amplify/graphql-transformer-core';
+import { InvalidDirectiveError, MappingTemplate, getGlobalSecondaryIndexes, getTable } from '@aws-amplify/graphql-transformer-core';
 import {
   TransformerContextProvider,
   TransformerPrepareStepContextProvider,
@@ -29,18 +29,6 @@ import { getSortKeyFields } from './schema';
 import { HasManyDirectiveConfiguration, HasOneDirectiveConfiguration } from './types';
 import { getConnectionAttributeName, getObjectPrimaryKey } from './utils';
 
-/**
- * Reads the list of global secondary indexes tracked on a DynamoDB L2 `Table` construct.
- *
- * `aws-cdk-lib` 2.260 renamed the (private) `globalSecondaryIndexes` array to `_globalSecondaryIndexes`
- * and now backs it with an `ArrayBox`, which still exposes the array-like `some`/`find`/`length` surface
- * and the same element shape (`{ indexName, keySchema }`). Amplify's own managed-table construct
- * (`AmplifyDynamoDBTable`) instead keeps its indexes on a public `globalSecondaryIndexes` array. Reading
- * `_globalSecondaryIndexes` first and falling back to `globalSecondaryIndexes` works for both table types
- * and preserves the duplicate-index-name detection rather than silently disabling it.
- */
-const getGlobalSecondaryIndexes = (table: any): any => table['_globalSecondaryIndexes'] ?? table.globalSecondaryIndexes;
-
 /**
  * Creates a GSI on the table of the `relatedType` based on the config's `references` / `referenceNodes`
  *

packages/amplify-graphql-transformer-core/API.md

@@ -250,6 +250,9 @@ export const getFieldNameFor: (op: Operation, typeName: string) => string;
 // @public (undocumented)
 export const getFilterInputName: (modelName: string) => string;
 
+// @public (undocumented)
+export const getGlobalSecondaryIndexes: (table: any) => any;
+
 // @public (undocumented)
 export const getImportedRDSTypeFromStrategyDbType: (dbType: ModelDataSourceStrategyDbType) => ImportedRDSType;
 

packages/amplify-graphql-transformer-core/src/index.ts

@@ -39,6 +39,7 @@ export {
   getDefaultStrategyNameForDbType,
   getField,
   getFilterInputName,
+  getGlobalSecondaryIndexes,
   getImportedRDSTypeFromStrategyDbType,
   getKeySchema,
   getModelDataSourceNameForTypeName,

packages/amplify-graphql-transformer-core/src/utils/index.ts

@@ -9,7 +9,7 @@ export {
 export { DirectiveWrapper, GetArgumentsOptions, generateGetArgumentsInput } from './directive-wrapper';
 export { collectDirectives, collectDirectivesByTypeNames } from './type-map-utils';
 export { stripDirectives } from './strip-directives';
-export { getTable, getKeySchema, getSortKeyFieldNames, getStrategyDbTypeFromTypeNode } from './schema-utils';
+export { getTable, getKeySchema, getGlobalSecondaryIndexes, getSortKeyFieldNames, getStrategyDbTypeFromTypeNode } from './schema-utils';
 export { DEFAULT_SCHEMA_DEFINITION } from './defaultSchema';
 export {
   constructArrayFieldsStatement,

packages/amplify-graphql-transformer-core/src/utils/schema-utils.ts

@@ -6,15 +6,26 @@ import { ListValueNode, ObjectTypeDefinitionNode, StringValueNode, TypeNode } fr
 import { ModelResourceIDs, getBaseType } from 'graphql-transformer-common';
 import { getModelDataSourceStrategy } from './model-datasource-strategy-utils';
 
+/**
+ * Reads the list of global secondary indexes tracked on a DynamoDB L2 `Table` construct.
+ *
+ * aws-cdk-lib 2.260 renamed the private `globalSecondaryIndexes` array on the DynamoDB L2 `Table` to
+ * `_globalSecondaryIndexes` (now an `ArrayBox` exposing the same `find`/`some`/`length` surface and the
+ * same `{ indexName, keySchema }` element shape); Amplify's managed-table construct keeps the public
+ * `globalSecondaryIndexes` array. This reads whichever exists (covers standard `Table` + Amplify managed
+ * table). Centralized so a future CDK rename is a one-line fix.
+ */
+export const getGlobalSecondaryIndexes = (table: any): any => table['_globalSecondaryIndexes'] ?? table.globalSecondaryIndexes;
+
 /**
  * getKeySchema
  */
 export const getKeySchema = (table: any, indexName?: string): any => {
-  // aws-cdk-lib 2.260 renamed the private `globalSecondaryIndexes`/`localSecondaryIndexes` arrays on the
-  // DynamoDB L2 `Table` to `_globalSecondaryIndexes`/`_localSecondaryIndexes` (now `ArrayBox`es exposing the
-  // same `find` surface and element shape). Amplify's managed-table construct keeps the public array names.
-  // Read the renamed fields first, falling back to the public ones so both table types resolve correctly.
-  const globalSecondaryIndexes = table['_globalSecondaryIndexes'] ?? table.globalSecondaryIndexes;
+  // aws-cdk-lib 2.260 renamed the private `localSecondaryIndexes` array on the DynamoDB L2 `Table` to
+  // `_localSecondaryIndexes` (now an `ArrayBox` exposing the same `find` surface and element shape).
+  // Amplify's managed-table construct keeps the public array name. Read the renamed field first, falling
+  // back to the public one so both table types resolve correctly.
+  const globalSecondaryIndexes = getGlobalSecondaryIndexes(table);
   const localSecondaryIndexes = table['_localSecondaryIndexes'] ?? table.localSecondaryIndexes;
   return (
     (