graphql-assert-transformer

A custom transformer of the amplify-cli. It can validate fields.

directive @assert(condition: String!, message: String, type: String) on FIELD_DEFINITION

Usage

1. Install package

npm install graphql-assert-transformer -D

or

yarn add graphql-assert-transformer -D

2. Setup custom transformer

Edit amplify/backend/api/<YOUR_API>/transform.conf.json and append "./graphql-assert-transformer" to transformers field.

    "transformers": [
      "graphql-assert-transformer"
    ]

3. Use @assert directive

Append @assert to target fields.

type Post @model {
  id: ID!
  title: String @assert(condition: ".length() > 3 && .matches(\"[a-zA-Z0-9]+\")")
  text: String @assert(condition: ".length() > 10")
  episode: Int @assert(condition: ". % 2 == 0")
}

You can refer the field itself by .. This transformer doesn't check type soundness, writing correct boolean expressions are up to you.

3.1 How it works

AppSync uses Apache Velocity for resolver mapping. It supports basic operators like logical operators. Besides, It supports Java methods. Thus, you can do whatever you want. But I'm not sure which Java version is used inside AppSync, you may find missing methods.

GraphQL Type	Java Class
ID	java.lang.String
String	java.lang.String
Int	java.lang.Integer
Float	java.lang.Double
Boolean	java.lang.Boolean
Array	java.util.ArrayList
Enum	java.lang.String

4. Export NODE_PATH

This step isn't necessary once https://github.com/aws-amplify/amplify-cli/pull/3236 merged.

export NODE_PATH=./node_modules

License

Fork of https://github.com/amazon-archives/aws-reinvent-2019-mobile-workshops/tree/master/MOB405/01%20-%20Finished

ISC

Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved. Copyright 2020 Hiroshi Ioka. All Rights Reserved.