How do you make closure-compiler understand NodeJS built-in module requires?

[Bradford Smith]

Is there anyone out there who has had success using closure-compiler with NodeJS and can tell us how to make closure-compiler OK with requires of built-in modules where there's no JS source file?

e.g.

const path = require('path');

Thanks,

Bradford

[Christopher Allen]

I contacted the engineer who originally checked these externs into the closure-compiler repository, and he sent the following illuminating but somewhat disappointing reply:

On 3 July 2018 at 12:28, Nick Santos wrote:

At the time (mid-2014), there were a bunch of closure-compiler forks around that were trying to reconcile closure-compiler's view of the world with NodeJS's view of the world. I saw the same type-checked externs for NodeJS builtins in a few different places.

We decided to check them into the closure-compiler repo. I hoped that this would:
1) reduce duplicated effort
2) demonstrate willingness from closure-compiler team in making them work
3) help the different forks converge towards a solution that was baked into closure-compiler 

 

In practice, this didn't happen. Typescript picked up steam. FlowJS came out later in 2014. Both of them had better answers to type-checking NodeJS apps.  So I think most of the people working on this decided to back those solutions instead.

I must say that this certainly parallels my experience of asking questions about more obscure corners of the closure-compiler type system and getting replies along the lines of "the answer to your question is <long and not entirely satisfactory solution>, but wait until you see this one neat trick using TypeScript!"

Also relevant-but-disappointing: this answer by Chad Killingsworth to "How do you define node_modules as externs in Closure Compiler?"

[Martin Probst]

This might not be an immediate solution to your problem, but my group builds and supports TypeScript / Closure interop tooling that might allow you to use both at the same time. See github.com/angular/tsickle (produce Closure-compliant JS from TS) and github.com/angular/clutz (produce .d.ts from Closure code).

We don't have a lot of experience using this with NodeJS, as Closure Compiler's strengths in optimization are a bit less useful there, but this tool chain is used for several very large web frontends at Google that have a mixed code base of TS and Closure JS code.

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[Sato Teppei]

Closure Compiler doesn't support external type definition (externs) for CommonJS or ES Modules.

Only global externs are supported.

See https://github.com/google/closure-compiler/issues/2479

It's a very important feature for users outside of Google.

2018年6月29日金曜日 3時07分43秒 UTC+9 Bradford Smith:

[Christopher Allen]

Also relevant-but-disappointing: this answer by Chad Killingsworth to "How do you define node_modules as externs in Closure Compiler?"

Following up on my own previous message: after a bit of experimentation, I found a way to write externs for the built-in modules by making npm-alike stubs for them.  Unfortunately it only works if you're using --checks-only, but hopefully the trick will be of use to others.