Implementation:Promptfoo Promptfoo ESM Loader

Knowledge Sources	Promptfoo_Promptfoo
Domains	Module_System, Runtime
Last Updated	2026-02-14 07:45 GMT

Overview

Concrete tool for loading ESM and CJS modules dynamically, resolving wrapper script paths, and handling module system interoperability across development and production environments.

Description

The ESM_Loader module (esm.ts) provides utilities for dynamic module loading that work correctly in both ESM and CJS contexts. It handles importing user-defined JavaScript/TypeScript modules (custom providers, assertions, transforms), resolving paths to language-specific wrapper scripts (Python, Ruby, Go), and providing the current directory reference that works across bundled and source environments. Results are cached for performance.

Usage

Import these utilities when code needs to dynamically load user-provided modules or locate wrapper scripts for non-JavaScript providers.

Code Reference

Source Location

• Repository: Promptfoo_Promptfoo
• File: src/esm.ts
• Lines: 1-461

Signature

export type WrapperType = 'python' | 'ruby' | 'golang';

export function getDirectory(): string

export function getWrapperDir(type: WrapperType): string

export async function importModule(
  modulePath: string,
  functionName?: string
): Promise<any>

Import

import { getDirectory, getWrapperDir, importModule } from './esm';

I/O Contract

Inputs

Name	Type	Required	Description
type	WrapperType	Yes	Language wrapper type: 'python', 'ruby', or 'golang'
modulePath	string	Yes	Path to the module to import (file:// or relative)
functionName	string	No	Specific named export to retrieve

Outputs

Name	Type	Description
directory	string	Absolute path to the current module directory
wrapperDir	string	Absolute path to the wrapper scripts directory
module	any	The imported module or specific exported function

Usage Examples

import { importModule, getWrapperDir } from './esm';

// Import a user's custom provider
const provider = await importModule('./my-provider.ts', 'default');

// Get Python wrapper script directory
const pythonDir = getWrapperDir('python');
// e.g., "/path/to/promptfoo/dist/src/python"

Related Pages

• Environment:Promptfoo_Promptfoo_Node_Runtime