esbuild bundling support external dependencies

[p-desaintchamas]

When bundling code with esbuild and using the dd-trace esbuild plugin, I run into an issue when resolving all dependencies, as some are specified as external for some useless dependencies I'm not using. Yet, dd-trace plugin still tries to resolve them.

Expected behaviour

external packages should not be resolved by the plugin

Actual behaviour

External packages are still resolved, causing issues when they are not added as dependencies

✘ [ERROR] Cannot find module 'tedious/package.json'
Require stack:
- /Users/**/node_modules/dd-trace/packages/datadog-esbuild/index.js
- /Users/**/node_modules/dd-trace/esbuild.js
- /Users/**/xbuild.config.js
- /Users/**/node_modules/@myscope/xbuild/dist/xbuild.js [plugin datadog-esbuild]

    node_modules/knex/lib/dialects/mssql/index.js:89:24:
      89 │     const tds = require('tedious');
         ╵                         ~~~~~~~~~

  This error came from the "onResolve" callback registered here:

    node_modules/dd-trace/packages/datadog-esbuild/index.js:38:8:
      38 │   build.onResolve({ filter: /.*/ }, args => {

Steps to reproduce

Sample project, with knex for example that has multiple external dependencies not useful, for example mysql if I'm using postgres, etc...

If I still try to add those dependencies, I run into another issue, which is that mysql2 is declared as instrumented, but the resolve is calling the package.json, which is not included in mysql2, causing the export to fail similarly. This would indicate that the list datadog-instrumentations/src/helpers/hooks.js is not entirely compatible.

✘ [ERROR] Package subpath './package.json' is not defined by "exports" in /Users/**/node_modules/mysql2/package.json [plugin datadog-esbuild]

    node_modules/dd-trace/packages/datadog-esbuild/index.js:45:40:
      45 │       const pathToPackageJson = require.resolve(`${packageName}/package.json`, { paths: [ args.resolveDir ] })

I think an easy fix would be to either:

• filter resolved modules on being or not listed as external in esbuild build config.
• add the ability for the user to specify a list of excluded modules when specifying the plugin, that would be complementary to the instrumented list provided by datadog.

Environment

• Operation system: Macos
• Node.js version: 16.19
• Tracer version: 4.0
• Agent version:
• Relevant library versions:

[p-desaintchamas]

For the mysql2 problem, I opened a merge request on their repo to allow the resolve to work as expected
sidorares/node-mysql2#2026

EDIT : PR has been merged and added to 3.3.3 release
I will test if it allow to fix today, but a support for external dependencies would still be the proper way to go, as this would enforce any user to include all libraries, and make the bundle size much more important