[regression-1.41.2] error: 'import', and 'export' cannot be used outside of module code

[rracariu]

Importing a .js file from node_modules is automatically treated as common js.
In Deno 1.42.1 this was not the case.

Something like:

import * as foo from 'node_modules/my_package/my_module.js'

Will result in:

error: 'import', and 'export' cannot be used outside of module code

This error goes away if you rename that module to my_module.mjs

Note: Deno is configured with the unstable "byonm" flag.

deno 1.41.2 (release, aarch64-apple-darwin)
v8 12.1.285.27
typescript 5.3.3

[dsherret]

Can you show a concrete example? The module is maybe indeed considered a common.js module (does the .js file have a corresponding package.json with { "type": "module" }?)

[rracariu]

The module is ES, it has the export clause that is where it actually errors out.

export function myFunction(args)...

The package.json contains a "module": "index.js" clause but is not marked as { "type": "module" }

What I want here to happen is to manually load a specific file from that package. I'm explicitly importing that file and I don't expect Deno to treat it in a special way. This works with Vite and Deno prior to recent update.

[dsherret]

I think Deno is now just correctly erroring the same way that Node errors with that package. Hard to tell without a concrete example, but here is the behaviour you're describing happening in Node:

> node main.js
(node:11392) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
V:\scratch\node_modules\package\index.js:1
export function myFunction() {}
^^^^^^

SyntaxError: Unexpected token 'export'
    at internalCompileFunction (node:internal/vm:77:18)
    at wrapSafe (node:internal/modules/cjs/loader:1290:20)
    at Module._compile (node:internal/modules/cjs/loader:1342:27)
    at Module._extensions..js (node:internal/modules/cjs/loader:1437:10)
    at Module.load (node:internal/modules/cjs/loader:1212:32)
    at Module._load (node:internal/modules/cjs/loader:1028:12)
    at cjsLoader (node:internal/modules/esm/translators:359:17)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/translators:308:7)
    at ModuleJob.run (node:internal/modules/esm/module_job:218:25)
    at async ModuleLoader.import (node:internal/modules/esm/loader:323:24)

Node.js v21.6.1

[rracariu]

node_modules/test/foo.js
node_modules/test/foo.mjs

foo.[m]js:

export function test() {}

test.js

import {test} from `node_modules/test/foo.js`

Node will not work because it defaults to commonjs, changing the extension of the import and test file to mjs will work. I'm not sure what are you saying here? Are you saying that Deno must follow Node's behavior in only loading .mjs files as modules? I don't think it is right to have this special casing for node_modules folder.

For reference, Bun does what I expect to do, it just loads the js file, same as prior Deno versions did.

[dsherret]

Can you share the package name please? It's hard to tell without a concrete example. It's sounding like Deno is now properly resolving the .js file in the npm package as CommonJS the same way as Node.js does, which is very important for Node compatiblity. Most likely the package just needs to fix its package.json

[rracariu]

What I want here is just to import a file. I don't want to import a package, and I don't want Deno to automatically assume that I want Node's behavior if the import path contains node_modules.

So, it is really not important what is the package I want to work with, it is just a path with some file in them.
But to entertain this, let's use @clerk/backend: "0.38.3"

test.js

import { AuthStatus } from './node_modules/@clerk/backend/dist/esm/index.js'
console.log(AuthStatus.SignedIn)

Deno 1.41.1

deno run test.js
signed-in

Bun 1.0.30

bun run test.js
signed-in

Node 21.7.0

node --experimental-detect-module test.js
signed-in

[dsherret]

What I want here is just to import a file. I don't want to import a package, and I don't want Deno to automatically assume that I want Node's behavior if the import path contains node_modules.

When using the unstable byonm feature or when not "nodeModulesDir": false with a package.json, Deno will use Node's rules for CJS and ESM detection within the node_modules directory. In this case, it is sounding like it is correctly determining that the .js file is considered a commonjs module.

So, it is really not important what is the package I want to work with, it is just a path with some file in them.
But to entertain this, let's use @clerk/backend: "0.38.3"

@clerk/backend exports ./dist/index.js for Node and Deno resolves that when importing that package as well (though it seems there is a bug related to package imports. I'm getting an incorrect Cannot find module '#crypto' and will fix that).

I've opened #22818 to add an unstable flag for resolving CJS modules like --experimental-detect-module, but overall it not treating that CJS defined module as CJS with BYONM was a bug that seems fixed and is now correctly raising the error you're encountering similar to Node by default. In Deno we want the Node compatiblity layer to behave as close to Node as possible, while providing unstable flags for enabling non-standard behaviour.

I'll try to get this unstable flag in the next minor release (or sooner), so I'd recommend staying on Deno 1.41.1 in the meantime.

[dsherret]

FWIW, @clerk/backend will load correctly in the next patch release of Deno once #22821 lands.

> cat main.js
import { Clerk } from '@clerk/backend';
console.log(Clerk);
> deno run main.js 
error: Uncaught (in promise) Error: Cannot find module '#crypto'
Require stack:
- V:\scratch\node_modules\@clerk\backend\dist\index.js
- V:\scratch\node_modules\@clerk\backend\dist\index.js
    at Function.Module._resolveFilename (node:module:622:15)
    at Function.Module._load (node:module:500:27)
    at Module.require (node:module:675:19)
    at require (node:module:789:16)
    at Object.<anonymous> (file:///V:/scratch/node_modules/@clerk/backend/dist/index.js:270:29)
    at Object.<anonymous> (file:///V:/scratch/node_modules/@clerk/backend/dist/index.js:3126:4)
    at Module._compile (node:module:731:34)
    at Object.Module._extensions..js (node:module:745:10)
    at Module.load (node:module:656:32)
    at Function.Module._load (node:module:537:12)

Next Deno patch:

> ../deno/target/debug/deno run main.js
[Function: Clerk]