Cannot detect `@swc-node/register` loaded by `fastify-cli` with the `-r` option

[zetaraku]

Prerequisites

• [X] I have written a descriptive issue title
• [X] I have searched existing issues to ensure the bug has not already been reported

Fastify version

4.28.1

Plugin version

5.10.0

Node.js version

20.x

Operating system

Windows

Operating system version (i.e. 20.04, 11.3, 10)

10

Description

I'm using fastify start -r @swc-node/register app.ts to start my app written in TypeScript.

However, this plugin cannot detect @swc-node/register loaded by fastify-cli and the following error is thrown:

Error: @fastify/autoload cannot import plugin at '~/fastify-app/plugins/sensible.ts'. To fix this error compile TypeScript to JavaScript or use 
'ts-node' to run your app.

Related PR:

PR https://github.com/fastify/fastify-autoload/pull/191 fixed the case with node -r @swc-node/register but not with fastify start -r @swc-node/register.

Current workaround:

I have to manually set the FASTIFY_AUTOLOAD_TYPESCRIPT environment variable.

Additional information:

The current checkPreloadModules() util checks the process._preload_modules array, but it's empty when the package is required with fastify-cli.

Link to code that reproduces the bug

https://github.com/zetaraku/fastify-app

Expected Behavior

The plugin should be able to detect the @swc-node/register package loaded by fastify start -r @swc-node/register.

[jean-michelet]

Is it an autoloader or a fastify-cli related issue? Maybe we should transfer this issue?

[zetaraku]

@jean-michelet

@fastify/autoload is relying on a Node.js internal variable to check if a module is loaded.

https://github.com/nodejs/node/blob/be7a0c578026dda29a1c9e76d5a0e04b71f25601/lib/internal/process/pre_execution.js#L259-L265

I don't think this is fastify-cli's issue since -r in fastify-cli is not guaranteed to be exactly the same as the -r in node, but it would be great if it's possible for fastify-cli to require modules the same as node does.

If not, maybe fastify-cli can provide another way for plugins to check for loaded modules, or @fastify/autoload can use another method to detect specific modules.

[jean-michelet]

If no answer from other collaborators, are you willing to investigate and push a PR on the right repo plz?

[zetaraku]

Imitating Node.js behavior by adding the following lines in fastify-cli's preloadCJSModules() does solve this issue, but I don't know if this is the right way to solve it.

I'll wait for more comments.

Object.defineProperty(process, '_preload_modules', {
  __proto__: null,
  writable: false,
  configurable: true,
  enumerable: true,
  value: opts.require,
})

[jean-michelet]

I don't know if this is the right way to solve it.

Wdyt @mcollina?

I still think this issue should be transfered to fastify-cli imo.

I have to manually set the FASTIFY_AUTOLOAD_TYPESCRIPT environment variable.

Or we can also document this workaround here.

[mcollina]

I think the problem is in this repo, we should not be checking that. Maybe we should check the require cache as well.

[jean-michelet]

Looking into it

[zetaraku]

Now I believe we should solve it in fastify-cli, because once require is called, the info of module name is lost and become many absolute paths in require.cache, checking it will become inefficient and non-trivial.