GraphQL Codegen Add Plugin

import { plugin, AddPluginConfig, VALID_PLACEMENTS } from "@graphql-codegen/add";

const { plugin } = require("@graphql-codegen/add");

import addPlugin from "@graphql-codegen/add";
// addPlugin.plugin is the plugin function

import type { AddPluginConfig } from "@graphql-codegen/add";

// codegen.ts configuration
import type { CodegenConfig } from '@graphql-codegen/cli';

const config: CodegenConfig = {
  schema: './schema.graphql',
  generates: {
    './src/generated/types.ts': {
      plugins: [
        'typescript',
        {
          add: {
            content: '/* eslint-disable */',
            placement: 'prepend'
          }
        }
      ]
    }
  }
};

export default config;

/**
 * Main plugin function for adding custom content to generated files
 * @param schema - GraphQL schema object
 * @param documents - Array of GraphQL document files
 * @param config - Plugin configuration object
 * @returns Promise resolving to plugin output with content placement
 */
export const plugin: PluginFunction<AddPluginConfig>;

type PluginFunction<TConfig> = (
  schema: GraphQLSchema,
  documents: Types.DocumentFile[],
  config: TConfig
) => Promise<Types.PluginOutput>;

/**
 * Configuration interface for the Add plugin
 */
export interface AddPluginConfig {
  /**
   * Position where content should be added in the generated file
   * @default "prepend"
   */
  placement?: 'prepend' | 'content' | 'append';
  
  /**
   * The actual content to add - can be a single string or array of strings.
   * You can also specify a path to a local file and the content will be loaded by codegen.
   * @required
   */
  content: string | string[];
}

/**
 * Array of valid placement values for the plugin configuration
 */
export const VALID_PLACEMENTS: AddPluginConfig['placement'][];
// Value: ['prepend', 'content', 'append']

// Add a single line at the top of generated files
{
  add: {
    content: '/* This file is auto-generated */',
    placement: 'prepend'
  }
}

// Add multiple lines using array
{
  add: {
    content: [
      '/* eslint-disable */',
      '// @ts-nocheck',
      ''
    ],
    placement: 'prepend'
  }
}

// Prepend content (default)
{
  add: {
    content: 'import "./custom-types";'
  }
}

// Append content at the end
{
  add: {
    content: 'export * from "./additional-exports";',
    placement: 'append'
  }
}

// Insert content in the middle
{
  add: {
    content: '// Custom content inserted here',
    placement: 'content'
  }
}

// Error examples:
// Error: Configuration provided for 'add' plugin is invalid: value of 'placement' field is not valid (valid values are: prepend, content, append)
// Error: Configuration provided for 'add' plugin is invalid: "content" is missing!

/**
 * Default export containing the plugin function
 */
export default {
  plugin: PluginFunction<AddPluginConfig>;
};

// From '@graphql-codegen/plugin-helpers'
interface Types {
  DocumentFile: {
    document: DocumentNode;
    location: string;
    rawSDL?: string;
  };
  
  PluginOutput: {
    content?: string | string[] | null;
    prepend?: string[];
    append?: string[];
  };
}

// From 'graphql'
class GraphQLSchema {
  // GraphQL schema representation
}

// Example output for 'prepend' placement:
{
  content: null,
  prepend: ['/* Custom content */', '// Another line']
}

// Example output for 'append' placement:
{
  content: null,
  append: ['export default generated;']
}

// Example output for 'content' placement:
// Note: This placement overrides the content property directly
{
  content: ['// Inserted content']
}