fix: Check if path segments includes node_modules explicitly

[icyJoseph]

What?

And edge case, as reported by #74404, where when the root dir name, contains the string node_modules, then Webpack errors are observed.

For example:

 ⨯ ./app/layout.tsx
Module parse failed: Unexpected token (1:12)
> import type { FC, PropsWithChildren } from "react";
| 
| const RootLayout: FC<PropsWithChildren> = ({

Why?

Although this is an edge case, it has been observed in user land, as per #74404

How?

Check if the node_modules is a path segment. Either of these works:

  return excludePath.split(path.sep).includes('node_modules')
  return excludePath.includes(path.sep + 'node_modules' + path.sep)
  return excludePath.includes('/node_modules/')

Or even a regexp match. I am just not sure about winOS and their path separators... and whether the path at this point is already normalised to /.

Fixes #74404

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 0eda7e3

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[Netail]

This change does not impact monorepo's right? Where the node_modules are sometimes located one or more directories above

[icyJoseph]

@Netail I think it should not. The issue here was a false positive on files, that excluded them from the loader, because their path contains node_modules.

So the webpack process ended up seeing a TS file, where it expected JavaScript.

For example, if you make a project where you have app/my-node_modules/page.tsx, where maybe you wanted to show off the node_modules used by your project, you'd also encounter this issue.

This PR would fix that, but it wouldn't fix an even more adventurous, app/node_modules/page.tsx

Then I guess we need to make the check more robust, with a regexp, or process.cwd() 🤔~ maybe I'll push another commit soon ~ and maybe, no promises, a unit test