Lab is not working with import syntax in my project about lab

[devinivy]

I've been thinking about this recently, and I agree. There are a couple paths we can take, e.g. integrating with c8 or rolling our own using similar techniques. I also wrote a module mo-walk for my own purposes recently that we could fork or expand on, for enumerating and running test files across both cjs and esm.

[kanongil]

Hmm, contrary to the docs, node will actually apply require.extensions to .js commonjs files through an import. This seems quite suspect, as it will need to determine the type before loading.

This means that it should be somewhat straightforward to support ESM-based test files, as long as all code that needs coverage checks are commonjs .js files. I'm not sure it makes much sense with that limitation, though.

[devinivy]

Unfortunately we don't support ES module projects at the moment, though I expect we'll probably see this working in the future. It's not ideal, but one option may be to use lab's transform option to "treat" it as a typescript project (which supports that syntax) even though it technically isn't. For the time being that is the only workaround I can think of 👍

[devinivy]

Actually, it may be slightly simpler now since you can use the --typescript flag rather than a transform, as of this recent PR: #1026.

[AnthonyCouval]

Oh ok, I probably missed that information about ES module project. Sorry.
Unfortunately even with --typescript flag it's not working. I've tried to put a tsconfig.json in my root app directory and install Typescript.
Is there anything else I should add ?

> [email protected] test D:\Projects\new-api
> lab  --typescript ./test/server.test.js

Error requiring file: D:\Projects\new-api\test\server.test.js
Cannot use import statement outside a module
D:\Projects\new-api\test\server.test.js:1
import * as Lab from '@hapi/lab';
^^^^^^

SyntaxError: Cannot use import statement outside a module
at wrapSafe (internal/modules/cjs/loader.js:988:16)
at Module._compile (internal/modules/cjs/loader.js:1036:27)
at Object.require.extensions.<computed> [as .js] (D:\Projects\new-api\node_modules\@hapi\lab\lib\modules\transform.js:41:28)
at Module.load (internal/modules/cjs/loader.js:937:32)
at Function.Module._load (internal/modules/cjs/loader.js:778:12)
at Module.require (internal/modules/cjs/loader.js:961:19)
at require (internal/modules/cjs/helpers.js:92:18)
at D:\Projects\new-api\node_modules\@hapi\lab\lib\cli.js:135:13
at Array.forEach (<anonymous>)
at Object.internals.traverse (D:\Projects\new-api\node_modules\@hapi\lab\lib\cli.js:129:15)
at Object.exports.run (D:\Projects\new-api\node_modules\@hapi\lab\lib\cli.js:60:31)
at main (D:\Projects\new-api\node_modules\@hapi\lab\bin\lab:56:50)
at Object.<anonymous> (D:\Projects\new-api\node_modules\@hapi\lab\bin\lab:60:1)
at Module._compile (internal/modules/cjs/loader.js:1072:14)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1101:10)
at Module.load (internal/modules/cjs/loader.js:937:32)
at Function.Module._load (internal/modules/cjs/loader.js:778:12)
at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:76:12)
at internal/main/run_main_module.js:17:47                                                                                     

My tsconfig.json :

{
    "compilerOptions": {
        "target": "es2021",
        "module": "commonjs",
        "moduleResolution": "node"
    }
}

[kanongil]

You will need to rename your files to end in .ts for that approach to have a chance of working. It will still fail, since you also need to add an export before const lab = ….

Looking into it, it will be a considerable task to enable ESM-based tests. Mostly because we rely on require.extensions to dynamically transform required code to instrument it for the coverage tool. This API has no stable replacement, and can only be enabled through a new experimental API that is quite different in v14 vs v16.

This would probably be simpler to do, if code coverage is updated to use the v8 instrumentation. Then we could use the existing require for typescript tests, and import for plain .js files.

[AnthonyCouval]

Thanks for all these explanations, it's clearer now.
FYI Jest has the same problem, it works with ESM but it's unstable and Mocha works but with some limitations.