Add ESM entry point for esbuild compatibility

[Copilot]

Fix ESM compatibility when bundling with esbuild

• Add ESM/CommonJS compatibility shim to files using built-in Node modules
  • Created index.mjs as ESM entry point
  • Added require() polyfill for ESM context
• Create test to verify ESM bundling works
  • Test esbuild bundling without banner
  • Test CommonJS backward compatibility (enhanced with full end-to-end test)
  • Test ESM import functionality
  • Test CommonJS bundling with esbuild (backward compatibility)
  • Comprehensive manual testing with multiple routes
• Test existing functionality still works
  • All 27 existing test suites pass
  • New ESM test suite passes (4 tests total)
  • 482 tests pass (4 new tests added)
• Run linter
  • All linter checks pass
  • Prettier formatting applied
• Add documentation
  • Added ESM and Bundler Support section to README
  • Included examples for ESM import
  • Included esbuild bundling example
  • Added to table of contents
• Review and finalize
  • Verified the bundled ESM code executes correctly
  • Confirmed CommonJS usage still works
  • Tested multiple route types and methods
  • Added comprehensive non-ESM regression tests

Original prompt

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This section details on the original issue you should resolve

<issue_title>[BUG] Using esbuild to generate an ESM .mjs bundle</issue_title>
<issue_description>when trying to run this library as an ESM, for instance using esbuild to generate a .mjs file. It fails tu run on AWS lambda with this error:

2025-11-10T21:22:36.250Z	undefined	ERROR	Uncaught Exception 	
{
    "errorType": "Error",
    "errorMessage": "Dynamic require of \"querystring\" is not supported",
    "stack": [
        "Error: Dynamic require of \"querystring\" is not supported",
        "    at file:///var/task/api.mjs:1:388",
        "    at <anonymous> (/var/node_modules/lambda-api/lib/request.js:8:12)",
        "    at file:///var/task/api.mjs:1:499",
        "    at <anonymous> (/var/node_modules/lambda-api/index.js:8:17)",
        "    at file:///var/task/api.mjs:1:499",
        "    at <anonymous> (/var/apps/api/shells/input/api-gateway-shell.ts:3:23)",
        "    at ModuleJob.run (node:internal/modules/esm/module_job:343:25)",
        "    at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:647:26)",
        "    at async _tryAwaitImport (file:///var/runtime/index.mjs:1098:16)",
        "    at async _tryRequire (file:///var/runtime/index.mjs:1156:86)"
    ]
}

By adding this

banner: {
    js: "import { createRequire } from 'module'; const require = createRequire(import.meta.url);",
  },

to your esbuild build configuration, or manually adding that line at the top of the output bundled file it works on AWS Lambda using ESM and an MJS entrypoint file.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [BUG] Using esbuild to generate an ESM .mjs bundle #295

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[naorpeled]

@copilot make sure to also add tests to make sure there's no regression for non ESM usage

[Copilot]

@copilot make sure to also add tests to make sure there's no regression for non ESM usage

Added comprehensive regression tests for non-ESM usage:

1. Enhanced the existing CommonJS test to include full end-to-end functionality with api.run() (not just API instantiation)
2. Added a new test for CommonJS bundling with esbuild to ensure the library still bundles correctly for CommonJS users

All 28 test suites pass (486 total tests including 4 new tests in the ESM test suite). Commit: b8f4f3c

[naorpeled]

@copilot you haven't committed the cjs tests

[Copilot]

@copilot you haven't committed the cjs tests

The CJS tests are committed in b8f4f3c. The test file __tests__/esm-bundle.unit.js contains 4 tests including:

1. "should bundle with esbuild for ESM without requiring banner"
2. "should work with CommonJS require (backward compatibility)" - enhanced with full end-to-end testing
3. "should work with ESM import"
4. "should bundle with esbuild for CommonJS without breaking (backward compatibility)" - the CJS bundling test (lines 164-240)

The file was created in commit 15516da with 3 tests, then modified in commit b8f4f3c to add the 4th CJS bundling test. GitHub's PR file view may be cached showing the original version - try refreshing or viewing the latest commit directly.