Runtime Injection

/**
 * Base class for runtime injection plugins
 * @template T - Configuration type for this runtime
 */
export declare class Runtime<T> {
  constructor(opts: RuntimeOpts<T>);
}

/**
 * Runtime plugin configuration interface
 * @template ConfigType - Type of configuration returned by loadConfig
 */
interface RuntimeOpts<ConfigType> {
  /** Load configuration for this runtime */
  loadConfig?: (args: {
    config: Config;
    options: PluginOptions;
    logger: PluginLogger;
    tracer: PluginTracer;
  }) => Promise<ConfigType> | ConfigType;

  /** Apply runtime code to a bundle (required) */
  apply(args: {
    bundle: NamedBundle;
    bundleGraph: BundleGraph<NamedBundle>;
    config: ConfigType;
    options: PluginOptions;
    logger: PluginLogger;
    tracer: PluginTracer;
  }): Promise<void | RuntimeAsset | Array<RuntimeAsset>>;
}

/**
 * Runtime asset to inject into bundles
 */
interface RuntimeAsset {
  /** File path for the runtime asset */
  filePath: FilePath;
  
  /** Runtime code content */
  code: string;
  
  /** Dependency that triggered this runtime */
  dependency?: Dependency;
  
  /** Whether this should be treated as an entry */
  isEntry?: boolean;
  
  /** Environment options for this runtime */
  env?: EnvironmentOptions;
  
  /** Whether to replace the original resolution */
  shouldReplaceResolution?: boolean;
}

import { Runtime } from "@parcel/plugin";

export default new Runtime({
  // Apply runtime injection (required)
  async apply({bundle, bundleGraph, options}) {
    // Check if this bundle needs HMR runtime
    if (options.mode === 'development' && options.hmrOptions) {
      return {
        filePath: '@parcel/runtime-hmr',
        code: `
          if (module.hot) {
            module.hot.accept(() => {
              window.location.reload();
            });
          }
        `,
        isEntry: false
      };
    }

    // Check if bundle has dynamic imports
    const hasDynamicImports = this.hasDynamicImports(bundle, bundleGraph);
    if (hasDynamicImports) {
      return {
        filePath: '@parcel/runtime-dynamic-import',
        code: this.generateDynamicImportRuntime(bundle, bundleGraph),
        isEntry: false
      };
    }
  },

  hasDynamicImports(bundle, bundleGraph) {
    const assets = bundleGraph.getBundleAssets(bundle);
    return assets.some(asset => 
      asset.getDependencies().some(dep => dep.isAsync)
    );
  },

  generateDynamicImportRuntime(bundle, bundleGraph) {
    return `
      window.__parcel_require_loader__ = function(id) {
        return import('./' + id + '.js');
      };
    `;
  }
});