### Example Input GraphQL Schema Files (GraphQL)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Illustrative examples of GraphQL schema files located in different directories, intended to be merged by the utility.

```graphql
~/moduleMain/schemas/Root.graphql:
type Query;

~/module1/schemas/Book.graphql:
extend type Query {
  bookById(id: ID!): Book
}
    
type Book {
  id: ID!
  authorId: ID!
}
 
~/module2/schemas/User.graphql:
extend type Query {
  userById(id: ID!): User
}
    
type User {
  id: ID!
  name: String!
}
```

--------------------------------

### Installing graphql-schema-utilities CLI (Shell)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Command to install the graphql-schema-utilities CLI tool globally using npm.

```sh
npm install -g graphql-schema-utilities
```

--------------------------------

### Example Merged GraphQL Schema Output (GraphQL)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Illustrative example of the resulting merged GraphQL schema file generated by the utility from the input schema files.

```graphql
type Query {
   userById(id: ID!): User
   bookById(id: ID!): Book
 }
 
 type User {
   id: ID!
   name: String!
 }
 
 type Book {
   id: ID!
   authorId: ID!
 }
```

--------------------------------

### Install Dependencies (Shell)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Installs project dependencies using the npm package manager. This command reads the `package.json` file and downloads the necessary packages into the `node_modules` directory.

```sh
npm install
```

--------------------------------

### Implementing a Custom GraphQL Validation Rule (TypeScript)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Example TypeScript code for creating a custom validation rule that checks if GraphQL operation names start with "Hawaii_". This rule can be used with the graphql-schema-utilities tool.

```typescript
import { GraphQLError } from 'graphql';

export function doesNotStartWithHawaii(operationName: string): string {
  return `"${operationName}" operation does not start with Hawaii_.`;
}

/**
 * Valid only if it starts with Hawaii_.
 * A GraphQL document is only valid if all defined operations starts with Hawaii_.
 */
export function OperationNameStartsWithHawaii(
  context: any,
): any {
  const knownOperationNames = Object.create(null);  
  return {
    OperationDefinition(node) {
      const operationName = node.name;
      if (operationName) {
        if (!operationName.value.startsWith('Hawaii_')) {
          
          context.reportError(
            new GraphQLError(
              doesNotStartWithHawaii(operationName.value)
            ),
          );
        } else {
          knownOperationNames[operationName.value] = operationName;
        }
      }
      return false;
    },
    FragmentDefinition: () => false,
  };
}
```

--------------------------------

### Run Build Script (Shell)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Executes the 'build' script defined in the project's `package.json` file. This is typically used to compile, bundle, or process source code for distribution.

```sh
npm run build
```

--------------------------------

### Running graphql-schema-utilities CLI (Shell)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Basic command to execute the graphql-schema-utilities CLI tool. It will attempt to merge schemas and validate operations based on default or configured paths.

```sh
>> graphql-schema-utilities
```

--------------------------------

### Using a Custom Validation Rule with CLI (Shell)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Command demonstrating how to apply a custom validation rule file (compiled JavaScript) to the validation process using the -r option.

```sh
>> graphql-schema-utilities -s "{./First_Directory/**/*.graphql,./Second_Directory/users/**/*.graphql}" -p "./path_to_directory/operations/*.graphql" -r "path/to/custom_rule.js"
```

--------------------------------

### Merging GraphQL Schema Files (Shell)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Command demonstrating how to merge GraphQL schema files from multiple directories using glob patterns with the -s option.

```sh
>> graphql-schema-utilities -s "{./First_Directory/**/*.graphql,./Second_Directory/users/**/*.graphql}"
```

--------------------------------

### Run Tests in Watch Mode (Shell)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Executes the 'test:watch' script defined in the project's `package.json` file. This command typically runs tests and watches for file changes, re-running tests automatically when changes are detected.

```sh
npm run test:watch
```

--------------------------------

### Merge GraphQL Schemas using graphql-schema-utilities (JS)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Demonstrates how to programmatically merge multiple GraphQL schema files using the `mergeGQLSchemas` function from the `graphql-schema-utilities` library. It takes a glob pattern as input and returns a promise that resolves with the merged schema or rejects with an error.

```js
const tools = require('graphql-schema-utilities');

const glob = "{./First_Directory/**/*.graphql,./Second_Directory/users/**/
  *.graphql}"
tools.mergeGQLSchemas(glob).then((schema) => {
  console.log('schema files were merged, and the valid schema is: ', schema)
})
  .catch((error) => {
    console.error(error)
  })
```

--------------------------------

### Validating GraphQL Operations (Shell)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Command demonstrating how to validate GraphQL operation files against a merged schema using glob patterns with the -s and -p options.

```sh
>> graphql-schema-utilities -s "{./First_Directory/**/*.graphql,./Second_Directory/users/**/*.graphql}" -p "./path_to_directory/operations/*.graphql"
```

--------------------------------

### Validate GraphQL Operations using graphql-schema-utilities (JS)

Source: https://github.com/awslabs/graphql-schema-utilities/blob/master/README.md

Shows how to validate GraphQL operations against a merged schema. It first merges schema files, then uses the resulting schema to validate query files specified by another glob pattern, logging the validation results.

```js
tools.mergeGQLSchemas('./schema/*.graphql').then((schema) => {
  tools.validateOperations('./queries/*.graphql', schema).then((results) => {
    console.log(results)
  })
})
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.