Swift 6 build error: Static property 'schema' is not concurrency-safe

[concavegit]

Environment information

System:
  OS: macOS 15.0
  CPU: (8) arm64 Apple M2
  Memory: 118.66 MB / 24.00 GB
  Shell: /bin/zsh
Binaries:
  Node: 22.9.0 - /opt/homebrew/bin/node
  Yarn: undefined - undefined
  npm: 10.8.3 - /opt/homebrew/bin/npm
  pnpm: undefined - undefined
NPM Packages:
  @aws-amplify/auth-construct: 1.3.1
  @aws-amplify/backend: 1.2.2
  @aws-amplify/backend-auth: 1.1.5
  @aws-amplify/backend-cli: 1.2.7
  @aws-amplify/backend-data: 1.1.4
  @aws-amplify/backend-deployer: 1.1.3
  @aws-amplify/backend-function: 1.4.1
  @aws-amplify/backend-output-schemas: 1.2.0
  @aws-amplify/backend-output-storage: 1.1.2
  @aws-amplify/backend-secret: 1.1.2
  @aws-amplify/backend-storage: 1.1.3
  @aws-amplify/cli-core: 1.1.3
  @aws-amplify/client-config: 1.3.1
  @aws-amplify/deployed-backend-client: 1.4.1
  @aws-amplify/form-generator: 1.0.2
  @aws-amplify/model-generator: 1.0.7
  @aws-amplify/platform-core: 1.1.0
  @aws-amplify/plugin-types: 1.2.2
  @aws-amplify/sandbox: 1.2.2
  @aws-amplify/schema-generator: 1.2.3
  aws-amplify: 6.6.2
  aws-cdk: 2.159.0
  aws-cdk-lib: 2.159.0
  typescript: 5.6.2
AWS environment variables:
  AWS_STS_REGIONAL_ENDPOINTS = regional
  AWS_NODEJS_CONNECTION_REUSE_ENABLED = 1
  AWS_SDK_LOAD_CONFIG = 1
No CDK environment variables

Describe the bug

I updated my iOS app from Swift 5 to Swift 6, and the build fails due to this error in the generated +Schema.swift files:

/Users/concaveusr/Projects/Kanai/Kanai/AmplifyModels/KanaiUserInfo+Schema.swift:23:21 Static property 'schema' is not concurrency-safe because non-'Sendable' type 'ModelSchema' may have shared mutable state

Note that putting @preconcurrency at the top of the generated Schema files suppresses the error, but I'm creating this issue to either add that automatically, or to even better find a way to make schema concurrency-safe.

Reproduction steps

Make any model in Amplify Gen 2 and put it in your Swift 6 Xcode project and try to build it.

[ykethan]

Hey,👋 thanks for raising this! I'm going to transfer this over to our API repository for better assistance 🙂

[dpilch]

ModelSchema actually is defined in the Amplify Swift library, so I think this issue will be solved there.

[thisisabhash]

We have released 2.51.0 with a bunch of fixes to resolve the Swift 6 build warnings: https://github.com/aws-amplify/amplify-swift/releases/tag/2.51.0

Please let us know if this is still an issue.