From e3dfa31cf22031a48324ab65d00561c8236a223b Mon Sep 17 00:00:00 2001
From: renevatium <rene@developmental.co.za>
Date: Thu, 20 Jun 2024 23:25:57 +0100
Subject: [PATCH 1/9] pass valid props to root stack

---
 .changeset/chatty-gifts-bathe.md              |  5 +++
 packages/backend/API.md                       |  6 ++-
 packages/backend/src/backend_factory.ts       | 20 ++++++++--
 packages/backend/src/default_stack_factory.ts | 11 +++++-
 packages/backend/src/engine/amplify_stack.ts  | 37 +++++++++++++++++--
 packages/backend/src/index.ts                 |  1 +
 .../project_environment_main_stack_creator.ts |  7 ++--
 7 files changed, 75 insertions(+), 12 deletions(-)
 create mode 100644 .changeset/chatty-gifts-bathe.md

diff --git a/.changeset/chatty-gifts-bathe.md b/.changeset/chatty-gifts-bathe.md
new file mode 100644
index 0000000000..cb7d99eba9
--- /dev/null
+++ b/.changeset/chatty-gifts-bathe.md
@@ -0,0 +1,5 @@
+---
+'@aws-amplify/backend': minor
+---
+
+Allow StackProps to be passed from defineBackend down to AmplifyStack for root Stack configuration
diff --git a/packages/backend/API.md b/packages/backend/API.md
index 1cb83ee09f..c61c7d8940 100644
--- a/packages/backend/API.md
+++ b/packages/backend/API.md
@@ -31,6 +31,7 @@ import { ResourceProvider } from '@aws-amplify/plugin-types';
 import { SsmEnvironmentEntriesGenerator } from '@aws-amplify/plugin-types';
 import { SsmEnvironmentEntry } from '@aws-amplify/plugin-types';
 import { Stack } from 'aws-cdk-lib';
+import { StackProps } from 'aws-cdk-lib';
 
 export { a }
 
@@ -70,7 +71,7 @@ export { ConstructFactoryGetInstanceProps }
 export { defineAuth }
 
 // @public
-export const defineBackend: <T extends DefineBackendProps>(constructFactories: T) => Backend<T>;
+export const defineBackend: <T extends DefineBackendProps>(constructFactories: T, mainStackProps?: MainStackProps) => Backend<T>;
 
 // @public (undocumented)
 export type DefineBackendProps = Record<string, ConstructFactory<ResourceProvider & Partial<ResourceAccessAcceptorFactory<never>>>> & {
@@ -89,6 +90,9 @@ export { GenerateContainerEntryProps }
 
 export { ImportPathVerifier }
 
+// @public
+export type MainStackProps = Pick<StackProps, 'description' | 'env' | 'tags' | 'analyticsReporting' | 'crossRegionReferences' | 'suppressTemplateIndentation'>;
+
 export { ResourceProvider }
 
 // @public
diff --git a/packages/backend/src/backend_factory.ts b/packages/backend/src/backend_factory.ts
index 208a82ea17..8a7923e547 100644
--- a/packages/backend/src/backend_factory.ts
+++ b/packages/backend/src/backend_factory.ts
@@ -27,6 +27,7 @@ import {
 import { CustomOutputsAccumulator } from './engine/custom_outputs_accumulator.js';
 import { ObjectAccumulator } from '@aws-amplify/platform-core';
 import { DefaultResourceNameValidator } from './engine/validations/default_resource_name_validator.js';
+import { MainStackProps } from './engine/amplify_stack.js';
 
 // Be very careful editing this value. It is the value used in the BI metrics to attribute stacks as Amplify root stacks
 const rootStackTypeIdentifier = 'root';
@@ -55,7 +56,15 @@ export class BackendFactory<
    * Initialize an Amplify backend with the given construct factories and in the given CDK App.
    * If no CDK App is specified a new one is created
    */
-  constructor(constructFactories: T, stack: Stack = createDefaultStack()) {
+  constructor(
+    constructFactories: T,
+    stack?: Stack,
+    mainStackProps?: MainStackProps
+  ) {
+    if (stack === undefined) {
+      stack = createDefaultStack(undefined, mainStackProps);
+    }
+
     new AttributionMetadataStorage().storeAttributionMetadata(
       stack,
       rootStackTypeIdentifier,
@@ -150,9 +159,14 @@ export class BackendFactory<
  * @param constructFactories - list of backend factories such as those created by `defineAuth` or `defineData`
  */
 export const defineBackend = <T extends DefineBackendProps>(
-  constructFactories: T
+  constructFactories: T,
+  mainStackProps?: MainStackProps
 ): Backend<T> => {
-  const backend = new BackendFactory(constructFactories);
+  const backend = new BackendFactory(
+    constructFactories,
+    undefined,
+    mainStackProps
+  );
   return {
     ...backend.resources,
     createStack: backend.createStack,
diff --git a/packages/backend/src/default_stack_factory.ts b/packages/backend/src/default_stack_factory.ts
index b084c6ce6d..26535c1e14 100644
--- a/packages/backend/src/default_stack_factory.ts
+++ b/packages/backend/src/default_stack_factory.ts
@@ -1,14 +1,21 @@
 import { App, Stack } from 'aws-cdk-lib';
 import { ProjectEnvironmentMainStackCreator } from './project_environment_main_stack_creator.js';
 import { getBackendIdentifier } from './backend_identifier.js';
+import { MainStackProps } from './engine/amplify_stack.js';
 
 /**
  * Creates a default CDK scope for the Amplify backend to use if no scope is provided to the constructor
  */
-export const createDefaultStack = (app = new App()): Stack => {
+export const createDefaultStack = (
+  app?: App,
+  props?: MainStackProps
+): Stack => {
+  if (app === undefined) {
+    app = new App();
+  }
   const mainStackCreator = new ProjectEnvironmentMainStackCreator(
     app,
     getBackendIdentifier(app)
   );
-  return mainStackCreator.getOrCreateMainStack();
+  return mainStackCreator.getOrCreateMainStack(props);
 };
diff --git a/packages/backend/src/engine/amplify_stack.ts b/packages/backend/src/engine/amplify_stack.ts
index 4c7475658b..ec8c87add1 100644
--- a/packages/backend/src/engine/amplify_stack.ts
+++ b/packages/backend/src/engine/amplify_stack.ts
@@ -1,8 +1,39 @@
 import { AmplifyFault } from '@aws-amplify/platform-core';
-import { Aspects, CfnElement, IAspect, Stack } from 'aws-cdk-lib';
+import { Aspects, CfnElement, IAspect, Stack, StackProps } from 'aws-cdk-lib';
 import { Role } from 'aws-cdk-lib/aws-iam';
 import { Construct, IConstruct } from 'constructs';
 
+/**
+ * Props for root CDK Stack
+ * @see {@link https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.StackProps.html | AWS documentation for aws-cdk-lib.StackProps}
+ *
+ * Props are picked to ensure explicit addition of new StackProps is required.
+ * Props incompatible with Amplify's intended Stack hierarchy, build or deployment processes are ommited:
+ * - stackName: Conflicts with dynamic resource naming.
+ * - synthesizer: Conflicts with managed deployments and resource references.
+ * - terminationProtection: Conflicts with sandbox/app delete.
+ * - permissionsBoundary: Conflicts with single root Stack ethos (i.e. Unable to create Role prior to `defineBackend`).
+ *
+ * Props are passed down from `defineBackend`:
+ * @example <caption>Set explicit region (e.g. for `new cloudfront.experimental.EdgeFunction`)</caption>
+ * ```
+ * defineBackend({}, {
+ *   env:
+ *     region: 'us-east-1' // Any valid AWS region
+ *   }
+ * })
+ * ```
+ */
+export type MainStackProps = Pick<
+  StackProps,
+  | 'description'
+  | 'env'
+  | 'tags'
+  | 'analyticsReporting'
+  | 'crossRegionReferences'
+  | 'suppressTemplateIndentation'
+>;
+
 /**
  * Amplify-specific Stack implementation to handle cross-cutting concerns for all Amplify stacks
  */
@@ -10,8 +41,8 @@ export class AmplifyStack extends Stack {
   /**
    * Default constructor
    */
-  constructor(scope: Construct, id: string) {
-    super(scope, id);
+  constructor(scope: Construct, id: string, props?: MainStackProps) {
+    super(scope, id, props);
     Aspects.of(this).add(new CognitoRoleTrustPolicyValidator());
   }
   /**
diff --git a/packages/backend/src/index.ts b/packages/backend/src/index.ts
index 039b5de54c..0ece4012a9 100644
--- a/packages/backend/src/index.ts
+++ b/packages/backend/src/index.ts
@@ -1,3 +1,4 @@
+export { type MainStackProps } from './engine/amplify_stack.js';
 export { defineBackend } from './backend_factory.js';
 export * from './backend.js';
 export * from './secret.js';
diff --git a/packages/backend/src/project_environment_main_stack_creator.ts b/packages/backend/src/project_environment_main_stack_creator.ts
index fbadb59b57..08f3353067 100644
--- a/packages/backend/src/project_environment_main_stack_creator.ts
+++ b/packages/backend/src/project_environment_main_stack_creator.ts
@@ -1,7 +1,7 @@
 import { BackendIdentifier, MainStackCreator } from '@aws-amplify/plugin-types';
 import { Construct } from 'constructs';
 import { Stack, Tags } from 'aws-cdk-lib';
-import { AmplifyStack } from './engine/amplify_stack.js';
+import { AmplifyStack, MainStackProps } from './engine/amplify_stack.js';
 import { BackendIdentifierConversions } from '@aws-amplify/platform-core';
 
 /**
@@ -20,11 +20,12 @@ export class ProjectEnvironmentMainStackCreator implements MainStackCreator {
   /**
    * Get a stack for this environment in the provided CDK scope
    */
-  getOrCreateMainStack = (): Stack => {
+  getOrCreateMainStack = (props?: MainStackProps): Stack => {
     if (this.mainStack === undefined) {
       this.mainStack = new AmplifyStack(
         this.scope,
-        BackendIdentifierConversions.toStackName(this.backendId)
+        BackendIdentifierConversions.toStackName(this.backendId),
+        props
       );
     }
 

From 93b77dcadb1e2d8531e8492fd91ccf2fa86f621e Mon Sep 17 00:00:00 2001
From: renevatium <rene@developmental.co.za>
Date: Mon, 24 Jun 2024 23:42:03 +0100
Subject: [PATCH 2/9] mainStackProps as key in DefineBackendProps

---
 packages/backend/API.md                 | 11 ++++++++---
 packages/backend/src/backend.ts         |  9 +++++++--
 packages/backend/src/backend_factory.ts | 22 +++++++++++-----------
 3 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/packages/backend/API.md b/packages/backend/API.md
index c61c7d8940..cbe0d4e600 100644
--- a/packages/backend/API.md
+++ b/packages/backend/API.md
@@ -42,7 +42,7 @@ export { AuthResources }
 export { AuthRoleName }
 
 // @public
-export type Backend<T extends DefineBackendProps> = BackendBase & {
+export type Backend<T extends DefineBackendConstructFactories> = BackendBase & {
     [K in keyof T]: Omit<ReturnType<T[K]['getInstance']>, keyof ResourceAccessAcceptorFactory>;
 };
 
@@ -71,13 +71,18 @@ export { ConstructFactoryGetInstanceProps }
 export { defineAuth }
 
 // @public
-export const defineBackend: <T extends DefineBackendProps>(constructFactories: T, mainStackProps?: MainStackProps) => Backend<T>;
+export const defineBackend: <T extends DefineBackendConstructFactories>(constructFactories: T, props?: DefineBackendProps) => Backend<T>;
 
 // @public (undocumented)
-export type DefineBackendProps = Record<string, ConstructFactory<ResourceProvider & Partial<ResourceAccessAcceptorFactory<never>>>> & {
+export type DefineBackendConstructFactories = Record<string, ConstructFactory<ResourceProvider & Partial<ResourceAccessAcceptorFactory<never>>>> & {
     [K in keyof BackendBase]?: never;
 };
 
+// @public (undocumented)
+export type DefineBackendProps = {
+    mainStackProps: MainStackProps;
+};
+
 export { defineData }
 
 export { defineFunction }
diff --git a/packages/backend/src/backend.ts b/packages/backend/src/backend.ts
index a4e767ada2..3dac6c6cac 100644
--- a/packages/backend/src/backend.ts
+++ b/packages/backend/src/backend.ts
@@ -6,6 +6,7 @@ import {
 } from '@aws-amplify/plugin-types';
 import { Stack } from 'aws-cdk-lib';
 import { ClientConfig } from '@aws-amplify/client-config';
+import { MainStackProps } from './index.internal.js';
 
 export type BackendBase = {
   createStack: (name: string) => Stack;
@@ -15,19 +16,23 @@ export type BackendBase = {
 };
 
 // Type that allows construct factories to be defined using any keys except those used in BackendHelpers
-export type DefineBackendProps = Record<
+export type DefineBackendConstructFactories = Record<
   string,
   ConstructFactory<
     ResourceProvider & Partial<ResourceAccessAcceptorFactory<never>>
   >
 > & { [K in keyof BackendBase]?: never };
 
+export type DefineBackendProps = {
+  mainStackProps: MainStackProps;
+};
+
 /**
  * Use `defineBackend` to create an instance of this type.
  * This object has the Amplify BackendBase methods on it for interacting with the backend.
  * It also has dynamic properties based on the resources passed into `defineBackend`
  */
-export type Backend<T extends DefineBackendProps> = BackendBase & {
+export type Backend<T extends DefineBackendConstructFactories> = BackendBase & {
   [K in keyof T]: Omit<
     ReturnType<T[K]['getInstance']>,
     keyof ResourceAccessAcceptorFactory
diff --git a/packages/backend/src/backend_factory.ts b/packages/backend/src/backend_factory.ts
index 8a7923e547..ae429cf91e 100644
--- a/packages/backend/src/backend_factory.ts
+++ b/packages/backend/src/backend_factory.ts
@@ -18,7 +18,11 @@ import { createDefaultStack } from './default_stack_factory.js';
 import { getBackendIdentifier } from './backend_identifier.js';
 import { platformOutputKey } from '@aws-amplify/backend-output-schemas';
 import { fileURLToPath } from 'node:url';
-import { Backend, DefineBackendProps } from './backend.js';
+import {
+  Backend,
+  DefineBackendConstructFactories,
+  DefineBackendProps,
+} from './backend.js';
 import { AmplifyBranchLinkerConstruct } from './engine/branch-linker/branch_linker_construct.js';
 import {
   ClientConfig,
@@ -27,7 +31,6 @@ import {
 import { CustomOutputsAccumulator } from './engine/custom_outputs_accumulator.js';
 import { ObjectAccumulator } from '@aws-amplify/platform-core';
 import { DefaultResourceNameValidator } from './engine/validations/default_resource_name_validator.js';
-import { MainStackProps } from './engine/amplify_stack.js';
 
 // Be very careful editing this value. It is the value used in the BI metrics to attribute stacks as Amplify root stacks
 const rootStackTypeIdentifier = 'root';
@@ -52,6 +55,7 @@ export class BackendFactory<
 
   private readonly stackResolver: StackResolver;
   private readonly customOutputsAccumulator: CustomOutputsAccumulator;
+
   /**
    * Initialize an Amplify backend with the given construct factories and in the given CDK App.
    * If no CDK App is specified a new one is created
@@ -59,10 +63,10 @@ export class BackendFactory<
   constructor(
     constructFactories: T,
     stack?: Stack,
-    mainStackProps?: MainStackProps
+    props?: DefineBackendProps
   ) {
     if (stack === undefined) {
-      stack = createDefaultStack(undefined, mainStackProps);
+      stack = createDefaultStack(undefined, props?.mainStackProps);
     }
 
     new AttributionMetadataStorage().storeAttributionMetadata(
@@ -158,15 +162,11 @@ export class BackendFactory<
  * Creates a new Amplify backend instance and returns it
  * @param constructFactories - list of backend factories such as those created by `defineAuth` or `defineData`
  */
-export const defineBackend = <T extends DefineBackendProps>(
+export const defineBackend = <T extends DefineBackendConstructFactories>(
   constructFactories: T,
-  mainStackProps?: MainStackProps
+  props?: DefineBackendProps
 ): Backend<T> => {
-  const backend = new BackendFactory(
-    constructFactories,
-    undefined,
-    mainStackProps
-  );
+  const backend = new BackendFactory(constructFactories, undefined, props);
   return {
     ...backend.resources,
     createStack: backend.createStack,

From e931b42cfb8eebc6a4023feff4fb41abd0e50560 Mon Sep 17 00:00:00 2001
From: renevatium <rene@developmental.co.za>
Date: Tue, 25 Jun 2024 00:01:33 +0100
Subject: [PATCH 3/9] pick only MainStackProps relevant to region handling

---
 packages/backend/src/engine/amplify_stack.ts | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/packages/backend/src/engine/amplify_stack.ts b/packages/backend/src/engine/amplify_stack.ts
index ec8c87add1..e775f69c10 100644
--- a/packages/backend/src/engine/amplify_stack.ts
+++ b/packages/backend/src/engine/amplify_stack.ts
@@ -8,7 +8,7 @@ import { Construct, IConstruct } from 'constructs';
  * @see {@link https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.StackProps.html | AWS documentation for aws-cdk-lib.StackProps}
  *
  * Props are picked to ensure explicit addition of new StackProps is required.
- * Props incompatible with Amplify's intended Stack hierarchy, build or deployment processes are ommited:
+ * Props incompatible with Amplify's intended Stack hierarchy, build or deployment processes should always be ommited:
  * - stackName: Conflicts with dynamic resource naming.
  * - synthesizer: Conflicts with managed deployments and resource references.
  * - terminationProtection: Conflicts with sandbox/app delete.
@@ -24,15 +24,7 @@ import { Construct, IConstruct } from 'constructs';
  * })
  * ```
  */
-export type MainStackProps = Pick<
-  StackProps,
-  | 'description'
-  | 'env'
-  | 'tags'
-  | 'analyticsReporting'
-  | 'crossRegionReferences'
-  | 'suppressTemplateIndentation'
->;
+export type MainStackProps = Pick<StackProps, 'env' | 'crossRegionReferences'>;
 
 /**
  * Amplify-specific Stack implementation to handle cross-cutting concerns for all Amplify stacks

From 1f79750ddad54ce488e4e430ddf810b22e5cce12 Mon Sep 17 00:00:00 2001
From: renevatium <rene@developmental.co.za>
Date: Tue, 25 Jun 2024 00:16:54 +0100
Subject: [PATCH 4/9] fix missing update:api for #e931b42

---
 packages/backend/API.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/backend/API.md b/packages/backend/API.md
index cbe0d4e600..76c52df0ca 100644
--- a/packages/backend/API.md
+++ b/packages/backend/API.md
@@ -96,7 +96,7 @@ export { GenerateContainerEntryProps }
 export { ImportPathVerifier }
 
 // @public
-export type MainStackProps = Pick<StackProps, 'description' | 'env' | 'tags' | 'analyticsReporting' | 'crossRegionReferences' | 'suppressTemplateIndentation'>;
+export type MainStackProps = Pick<StackProps, 'env' | 'crossRegionReferences'>;
 
 export { ResourceProvider }
 

From 28a8743b72d82271ff850ac4e27ea09ae0ff28cf Mon Sep 17 00:00:00 2001
From: renevatium <rene@developmental.co.za>
Date: Tue, 25 Jun 2024 00:30:24 +0100
Subject: [PATCH 5/9] mainStackProps in DefineBackendProps should be optional

---
 packages/backend/src/backend.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/backend/src/backend.ts b/packages/backend/src/backend.ts
index 3dac6c6cac..6698d34ba6 100644
--- a/packages/backend/src/backend.ts
+++ b/packages/backend/src/backend.ts
@@ -24,7 +24,7 @@ export type DefineBackendConstructFactories = Record<
 > & { [K in keyof BackendBase]?: never };
 
 export type DefineBackendProps = {
-  mainStackProps: MainStackProps;
+  mainStackProps?: MainStackProps;
 };
 
 /**

From 93e0222a06aafaf8a71dff085f062a77d59ef460 Mon Sep 17 00:00:00 2001
From: renevatium <rene@developmental.co.za>
Date: Tue, 25 Jun 2024 00:45:00 +0100
Subject: [PATCH 6/9] better import path for MainStackProps

---
 packages/backend/src/backend.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/backend/src/backend.ts b/packages/backend/src/backend.ts
index 6698d34ba6..7e49411762 100644
--- a/packages/backend/src/backend.ts
+++ b/packages/backend/src/backend.ts
@@ -6,7 +6,7 @@ import {
 } from '@aws-amplify/plugin-types';
 import { Stack } from 'aws-cdk-lib';
 import { ClientConfig } from '@aws-amplify/client-config';
-import { MainStackProps } from './index.internal.js';
+import { MainStackProps } from './engine/amplify_stack.js';
 
 export type BackendBase = {
   createStack: (name: string) => Stack;

From 3b24347294b12115cdb8ca80f822d89fd8706169 Mon Sep 17 00:00:00 2001
From: renevatium <rene@developmental.co.za>
Date: Tue, 25 Jun 2024 00:51:43 +0100
Subject: [PATCH 7/9] BackendFactory constructor overloading for conditional
 prop exclusion

---
 packages/backend/src/backend_factory.ts | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/packages/backend/src/backend_factory.ts b/packages/backend/src/backend_factory.ts
index ae429cf91e..1f86d244e5 100644
--- a/packages/backend/src/backend_factory.ts
+++ b/packages/backend/src/backend_factory.ts
@@ -39,6 +39,9 @@ const rootStackTypeIdentifier = 'root';
 const DEFAULT_CLIENT_CONFIG_VERSION_FOR_BACKEND_ADD_OUTPUT =
   ClientConfigVersionOption.V1;
 
+// Stricter Omit for constructor overloading
+type ExplicitOmit<T, K extends keyof T> = Pick<T, Exclude<keyof T, K>>;
+
 /**
  * Factory that collects and instantiates all the Amplify backend constructs
  */
@@ -56,6 +59,19 @@ export class BackendFactory<
   private readonly stackResolver: StackResolver;
   private readonly customOutputsAccumulator: CustomOutputsAccumulator;
 
+  /**
+   *
+   */
+  constructor(
+    constructFactories: T,
+    stack: Stack,
+    props?: ExplicitOmit<DefineBackendProps, 'mainStackProps'>
+  );
+  /**
+   *
+   */
+  constructor(constructFactories: T, stack?: never, props?: DefineBackendProps);
+
   /**
    * Initialize an Amplify backend with the given construct factories and in the given CDK App.
    * If no CDK App is specified a new one is created

From 279f39369c736ba396c888464f3b45527d8e5748 Mon Sep 17 00:00:00 2001
From: renevatium <rene@developmental.co.za>
Date: Tue, 25 Jun 2024 06:26:32 +0100
Subject: [PATCH 8/9] revert DefineBackendConstructFactories back to
 DefineBackendProps and rename new prop

---
 packages/backend/src/backend.ts         |  6 +++---
 packages/backend/src/backend_factory.ts | 18 +++++++++++-------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/packages/backend/src/backend.ts b/packages/backend/src/backend.ts
index 7e49411762..055cde97d0 100644
--- a/packages/backend/src/backend.ts
+++ b/packages/backend/src/backend.ts
@@ -16,14 +16,14 @@ export type BackendBase = {
 };
 
 // Type that allows construct factories to be defined using any keys except those used in BackendHelpers
-export type DefineBackendConstructFactories = Record<
+export type DefineBackendProps = Record<
   string,
   ConstructFactory<
     ResourceProvider & Partial<ResourceAccessAcceptorFactory<never>>
   >
 > & { [K in keyof BackendBase]?: never };
 
-export type DefineBackendProps = {
+export type DefineBackendOptions = {
   mainStackProps?: MainStackProps;
 };
 
@@ -32,7 +32,7 @@ export type DefineBackendProps = {
  * This object has the Amplify BackendBase methods on it for interacting with the backend.
  * It also has dynamic properties based on the resources passed into `defineBackend`
  */
-export type Backend<T extends DefineBackendConstructFactories> = BackendBase & {
+export type Backend<T extends DefineBackendProps> = BackendBase & {
   [K in keyof T]: Omit<
     ReturnType<T[K]['getInstance']>,
     keyof ResourceAccessAcceptorFactory
diff --git a/packages/backend/src/backend_factory.ts b/packages/backend/src/backend_factory.ts
index 1f86d244e5..ea66f1f82a 100644
--- a/packages/backend/src/backend_factory.ts
+++ b/packages/backend/src/backend_factory.ts
@@ -20,7 +20,7 @@ import { platformOutputKey } from '@aws-amplify/backend-output-schemas';
 import { fileURLToPath } from 'node:url';
 import {
   Backend,
-  DefineBackendConstructFactories,
+  DefineBackendOptions,
   DefineBackendProps,
 } from './backend.js';
 import { AmplifyBranchLinkerConstruct } from './engine/branch-linker/branch_linker_construct.js';
@@ -60,17 +60,21 @@ export class BackendFactory<
   private readonly customOutputsAccumulator: CustomOutputsAccumulator;
 
   /**
-   *
+   * stack and props.mainStackProps are mutually exclusive
    */
   constructor(
     constructFactories: T,
     stack: Stack,
-    props?: ExplicitOmit<DefineBackendProps, 'mainStackProps'>
+    props?: ExplicitOmit<DefineBackendOptions, 'mainStackProps'>
   );
   /**
    *
    */
-  constructor(constructFactories: T, stack?: never, props?: DefineBackendProps);
+  constructor(
+    constructFactories: T,
+    stack?: never,
+    props?: DefineBackendOptions
+  );
 
   /**
    * Initialize an Amplify backend with the given construct factories and in the given CDK App.
@@ -79,7 +83,7 @@ export class BackendFactory<
   constructor(
     constructFactories: T,
     stack?: Stack,
-    props?: DefineBackendProps
+    props?: DefineBackendOptions
   ) {
     if (stack === undefined) {
       stack = createDefaultStack(undefined, props?.mainStackProps);
@@ -178,9 +182,9 @@ export class BackendFactory<
  * Creates a new Amplify backend instance and returns it
  * @param constructFactories - list of backend factories such as those created by `defineAuth` or `defineData`
  */
-export const defineBackend = <T extends DefineBackendConstructFactories>(
+export const defineBackend = <T extends DefineBackendProps>(
   constructFactories: T,
-  props?: DefineBackendProps
+  props?: DefineBackendOptions
 ): Backend<T> => {
   const backend = new BackendFactory(constructFactories, undefined, props);
   return {

From 5fb4e0328052cd45aaabe378ae0190eaed5643ed Mon Sep 17 00:00:00 2001
From: renevatium <rene@developmental.co.za>
Date: Tue, 25 Jun 2024 06:30:35 +0100
Subject: [PATCH 9/9] revert and update backend API doc

---
 packages/backend/API.md | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/packages/backend/API.md b/packages/backend/API.md
index 76c52df0ca..7efc2c19a5 100644
--- a/packages/backend/API.md
+++ b/packages/backend/API.md
@@ -42,7 +42,7 @@ export { AuthResources }
 export { AuthRoleName }
 
 // @public
-export type Backend<T extends DefineBackendConstructFactories> = BackendBase & {
+export type Backend<T extends DefineBackendProps> = BackendBase & {
     [K in keyof T]: Omit<ReturnType<T[K]['getInstance']>, keyof ResourceAccessAcceptorFactory>;
 };
 
@@ -71,16 +71,16 @@ export { ConstructFactoryGetInstanceProps }
 export { defineAuth }
 
 // @public
-export const defineBackend: <T extends DefineBackendConstructFactories>(constructFactories: T, props?: DefineBackendProps) => Backend<T>;
+export const defineBackend: <T extends DefineBackendProps>(constructFactories: T, props?: DefineBackendOptions) => Backend<T>;
 
 // @public (undocumented)
-export type DefineBackendConstructFactories = Record<string, ConstructFactory<ResourceProvider & Partial<ResourceAccessAcceptorFactory<never>>>> & {
-    [K in keyof BackendBase]?: never;
+export type DefineBackendOptions = {
+    mainStackProps?: MainStackProps;
 };
 
 // @public (undocumented)
-export type DefineBackendProps = {
-    mainStackProps: MainStackProps;
+export type DefineBackendProps = Record<string, ConstructFactory<ResourceProvider & Partial<ResourceAccessAcceptorFactory<never>>>> & {
+    [K in keyof BackendBase]?: never;
 };
 
 export { defineData }