Generated GraphQL output is wrong for mutation with array of customType

[TimRoadley]

Environment information

System:
  OS: macOS 15.6
  CPU: (14) arm64 Apple M4 Pro
  Memory: 173.95 MB / 24.00 GB
  Shell: /bin/zsh
Binaries:
  Node: 20.19.2 - ~/.nvm/versions/node/v20.19.2/bin/node
  Yarn: 1.22.22 - /opt/homebrew/bin/yarn
  npm: 10.8.2 - ~/.nvm/versions/node/v20.19.2/bin/npm
  pnpm: undefined - undefined
NPM Packages:
  @aws-amplify/auth-construct: 1.8.1
  @aws-amplify/backend: 1.16.1
  @aws-amplify/backend-ai: Not Found
  @aws-amplify/backend-auth: 1.7.1
  @aws-amplify/backend-cli: 1.8.0
  @aws-amplify/backend-data: 1.6.1
  @aws-amplify/backend-deployer: 2.1.3
  @aws-amplify/backend-function: 1.14.1
  @aws-amplify/backend-output-schemas: 1.7.0
  @aws-amplify/backend-output-storage: 1.3.1
  @aws-amplify/backend-secret: 1.4.0
  @aws-amplify/backend-storage: 1.4.1
  @aws-amplify/cli-core: 2.2.1
  @aws-amplify/client-config: 1.8.0
  @aws-amplify/data-construct: 1.16.3
  @aws-amplify/data-schema: 1.21.1
  @aws-amplify/deployed-backend-client: 1.8.0
  @aws-amplify/form-generator: 1.2.4
  @aws-amplify/model-generator: 1.2.0
  @aws-amplify/platform-core: 1.10.0
  @aws-amplify/plugin-types: 1.11.0
  @aws-amplify/sandbox: 2.1.2
  @aws-amplify/schema-generator: 1.4.0
  @aws-cdk/toolkit-lib: 1.1.1
  aws-amplify: 6.15.5
  aws-cdk-lib: 2.204.0
  typescript: 5.9.2

Data packages

my_amplify_app@1.0.0 /Users/tim/Documents/GitHub/mp365/cta-test/my_amplify_app
├─┬ @aws-amplify/backend-cli@1.8.0
│ └─┬ @aws-amplify/schema-generator@1.4.0
│   └── @aws-amplify/graphql-schema-generator@0.11.12
└─┬ @aws-amplify/backend@1.16.1
  └─┬ @aws-amplify/backend-data@1.6.1
    └── @aws-amplify/data-construct@1.16.3

Description

My resource.ts is configured with an array of tags, which is a custom type. This schema has a mutation for batch upserts, that relies on BatchUpsert.js.

Running npx ampx generate graphql-client-code --out amplify/graphql generates API.ts, which correctly sets tags as an Array for everything except for TodoUpsertInput.

Unfortunately I need TodoUpsertInput to properly expect an array and not a single object, so that I can upsert in batches.

Thanks in advance for your help, let me know if any further information is required, it should be pretty easy to reproduce.

[pahud]

Current Behavior

The GraphQL client code generator produces inconsistent TypeScript types:

// ✅ Correct - Other generated types
export type Todo = {
  tags?: Array<Tag | null> | null;
  // ... other fields
};

// ❌ Incorrect - TodoUpsertInput type  
export type TodoUpsertInput = {
  tags?: Tag | null;  // Should be Array<Tag | null> | null
  // ... other fields
};

Expected Behavior

All generated types should consistently handle array fields:

// ✅ Expected - TodoUpsertInput should be
export type TodoUpsertInput = {
  tags?: Array<Tag | null> | null;  // Consistent with other types
  // ... other fields
};

---

Hi @TimRoadley,

Thank you for reporting this issue! You've identified an inconsistency in how the GraphQL client code generator handles array fields of custom types in mutation input types.

The problem appears to be in the type transformation logic within the InputFieldWrapper.fromField() method, where array type information is being lost when processing custom types for input objects like TodoUpsertInput.

This is a legitimate bug that affects batch operations with custom type arrays. The fix would involve preserving the ListType wrapper when transforming custom types from ObjectType to InputType definitions.

Possible Fixes/Solutions

1. Fix Array Type Preservation: Modify the InputFieldWrapper.fromField() method to preserve ListType wrappers when processing custom types:

// In InputFieldWrapper.fromField()
if (isScalar(field.type) || isEnum(field.type, document)) {
  type = field.type;
} else {
  // Preserve array structure for custom types
  if (isListType(field.type)) {
    const baseType = getBaseType(field.type);
    const inputTypeName = ModelResourceIDs.NonModelInputObjectName(baseType);
    type = withNamedNodeNamed(field.type, inputTypeName);
  } else {
    type = withNamedNodeNamed(field.type, ModelResourceIDs.NonModelInputObjectName(getBaseType(field.type)));
  }
}

2. Update Type Transformation Logic: Ensure that the mutation input field generation in makeCreateInputField, makeUpdateInputField, and related functions correctly handles array types.

3. Add Test Coverage: Create comprehensive tests for array custom type handling in GraphQL client code generation.

---

Would you be interested in contributing a fix for this issue? The changes would primarily be in:

• packages/amplify-graphql-transformer-core/src/wrappers/object-definition-wrapper.ts
• packages/amplify-graphql-model-transformer/src/graphql-types/mutation.ts

I can provide more detailed guidance on the implementation approach if you'd like to work on this!

[TimRoadley]

Hi @pahud ,

Thanks for confirming the bug, I'm reading the contributing guide now and will see if I can fix the issue locally.

Cheers,
Tim

[TimRoadley]

I have a potential fix and test case passed, however to be certain of the fix I need to use the fix in my sample app.

The CONTRIBUTING.md document tells me to run amplify-dev for testing, however that's for Gen 1.

I assume the eqivelant in gen 2 is my npx ampx generate graphql-client-code command, however I expect that needs to somehow reference my fork branch with the potential fixes.

It's unclear how to get my fixed code into my sample app. I will keep investigating, however guidance would be appreciated, thanks in advance!

[TimRoadley]

@pahud I think InputFieldWrapper.fromField is for Gen 1. I believe I have fixed this for Gen 2 by altering https://github.com/aws-amplify/amplify-data/blob/main/packages/data-schema/src/SchemaProcessor.ts.

I have created a draft PR aws-amplify/amplify-data#619

Note that in my testing I was able to successfully fix this issue:

BEFORE:

AFTER:

[TimRoadley]

Full fix + reproduction steps

This is the reproduction of the issue and the interim solution until the fix hits production.

Issue Reproduction

yarn create expo-app test_app -t expo-template-blank-typescript

cd test_app

yarn create amplify

yarn add \
  @aws-amplify/ui-react-native \
  @aws-amplify/react-native \
  aws-amplify \
  @react-native-community/netinfo \
  @react-native-async-storage/async-storage \
  react-native-safe-area-context@^4.2.5 \
  react-native-get-random-values \
  react-native-url-polyfill

Copy in BatchUpsert.js and resource.ts from data.zip

npx ampx sandbox
npx ampx generate graphql-client-code --out amplify/graphql

** You should now see the issue in /amplify/graphql/API.ts The issue is that tags is not an array **

export type TodoUpsertInput = {
  content?: string | null,
  tags?: TodoTagTypeInput | null,
  updatedTs?: number | null,
};

The Fix

This was the only change I made to https://github.com/aws-amplify/amplify-data/blob/main/packages/data-schema/src/SchemaProcessor.ts:

To leverage that fix though, your app needs to use build output in /node_modules/@aws-amplify/data-schema/dist, not just that source file.

I've extracted the 5 specific files this impacts, so people can use the fix by copying in the data-schema-fix.zip then run apply-fix.js

Optional: set apply-fix.js as a postinstall script in package.json so you can use it in production until the real package is fixed in aws-amplify

Add this to package.json so it runs after yarn install automatically

  "scripts": {
    "postinstall": "node data-schema-fix/apply-fix.js"
  },

The Result

Regenerate the schema with the following commands:

npx ampx sandbox
npx ampx generate graphql-client-code --out amplify/graphql

** You should now see the FIX in /amplify/graphql/API.ts **

export type TodoUpsertInput = {
  content?: string | null,
  tags?: Array< TodoTagTypeInput | null > | null,
  updatedTs?: number | null,
};

Note

If this fix doesn't seem to be working in your sandbox, delete it completely and try again