package.json should include an explicit "main" entry

[mstange]

This was previously discussed in #94: It's good practice to include a "main": "main-file.js" entry in package.json, so that the generated npm package is usable without specifying a file name.

The current workaround is to use wasm-pack build --out-name index, or to manually adjust package.json after the build. However, even with the main file being called "index.js", it would be better to have an explicit "main": "index.js" entry, according to this comment by @ljharb, who is on the nodejs Modules team.

[ljharb]

As long as you're making changes, it'd be also good to add:

"exports": {
  ".": "./index.js",
  "./package.json": "./package.json"
},

since adding that field is usually a breaking change, so it's good to add it earlier

[DoctorBracewell]

Running into this exact issue - one of the build tools I'm using to bundle the output package uses node's require.resolve(packageName) function which complains that it can't find the package if the package.json doesn't contain a main field.

I might take a look into submitting a PR that adds an explicit "main": "file-name.js" field to the package.json - can anyone think if that would be a breaking change or have any unintended side-effects?

[DoctorBracewell]

Taking a look at the package.json generation code and output for each build target it seems like the nodejs target is the only one that includes a main field, other targets such as bundler or no-modules use properties such as module or browser, which according to this SO answer are not officially supported by node (but still recognised by a number of different bunders/package managers etc.)

Given Ijharb's comment, I'd assume it best to just include a main property for the package.json regardless of the build target? Which shouldn't be too hard because the value that main should have exists in some form for each target output anyway.

[ljharb]

Yes, always include "main" as CJS; there's no advantage to omitting it.

[DogLooksGood]

Hey, any news. I saw the PR is blocked?
The main property is kinda necessary for using with bundlers like Vite.

[ronsims2]

@DogLooksGood, I ran into the same problem and I wrote a couple of scripts to work around the missing main by adding it: https://gist.github.com/ronsims2/78ed52583f84056969577286b881c0bc

[DogLooksGood]

@ronsims2 Yeah, we are using a patch to add a "main" entry