Missing documentation for exports alternative paths

[ernestostifano]

Affected URL(s)

https://nodejs.org/api/packages.html

Description of the problem

Packages documentation is really helpful to understand motivations and practical usage of exports, from the simplest setup to nested conditions, wildcards, etc. However, it seems to lack a description and examples of "alternative paths" within exports, which I think is really powerful stuff, but currently underrated and not very popular (maybe because of the lack in documentation).

With "alternative paths" what I mean is using arrays as follows:

{
    "exports": {
        ".": {
            "development": {
                "types": "./src/index.ts",
                "import": "./src/index.js",
                "require": "./src/index.cjs",
                "default": "./src/index.cjs"
            },
            "import": {
                "types": "./types/index.d.ts",
                "default": [
                    "./src/index.js",
                    "./esm/index.js"
                ]
            },
            "require": [
                "./src/index.cjs",
                "./cjs/index.cjs"
            ],
            "default": [
                "./src/index.cjs",
                "./cjs/index.cjs"
            ]
        }
    }
}

The only hint I found in the documentation, is string[] syntax under exports.

Beside that, there are some mentions around:

• Webpack's official docs citing Node.js behaviour: https://webpack.js.org/guides/package-exports/#alternatives.
• Notable TypeScript issue requesting aligning to Node.js behaviour: Conditional exports doesn't respect alternative paths #37928

I think that "alternative paths" is the perfect solution for situations like using your own package without having to build it first during development (e.g., TypeScript, transpiling, polyfilling, etc.)

If there is a spec I would love to update the docs myself.

[ernestostifano]

I am just figuring that the array paths are matched without caring if the specified file exists or not. In that case, what is the practical purpose of the array? I mean, an invalid path is always invalid, right?

EDIT: Found the answer here. However, it's a shame because it would have been very helpful solving today's limitations instead of future compatibility.