Exploring the Concept of "Barrel" Modules and NPM Package Publishing
A concept known as a "barrel" is used to re-export modules within an index.ts file in order to streamline imports and organization. This technique allows for importing modules from a folder using only the directory name, simplifying the import process.
While this method works well within a project, questions arise when considering publishing a package to NPM. How can one import directly from the package root? The structure includes a dist directory with an index.js, index.d.ts, and a src folder, enabling imports from package/dist.
Certain projects like Nest.js' TypeORM package include transpiled index files at their root by manually adding them to the package. There's confusion about how this process works, especially since the build places everything in the dist directory. Copy-pasting the transpiled index files manually seems like a possible solution, but manual tasks often lead to errors. What is the best approach in this scenario?
An additional point of confusion arises regarding the root index.ts file containing only export * from "./dist". While this may seem straightforward, it results in a compiler error (TS2306). How does this mechanism function effectively?
This discussion delves into complex topics related to module exports, folder structures, and NPM packaging. Your insight and expertise on these matters are greatly appreciated.
For further details, see the comprehensive directory structure:
.
├── dist
│ ├── src
│ │ ├── loan
│ │ ├── index.d.ts
│ │ ├── index.js
│ │ ├── loan.model.d.ts
│ │ ├── loan.model.js
│ │ ├── loan.service.d.ts
│ │ └── loan.service.js
│ │ └── user
│ │ ├── index.d.ts
│ │ ├── index.js
│ │ ├── user.model.d.ts
│ │ ├── user.model.js
│ │ ├── user.service.d.ts
│ │ └── user.service.js
│ ├── index.d.ts
│ ├── index.js
│ └── index.js.map
├── node_modules
├── src
│ ├── loans
│ │ ├── index.ts
│ │ ├── loan.model.ts
│ │ └── loan.service.ts
│ └── user
│ ├── index.ts
│ ├── user.model.ts
│ └── user.service.ts
├── index.ts
├── package.json
├── package-lock.json
├── README.md
└── tsconfig.json
Review of the package.json configuration:
{
"name": "totally-unique-package-name",
"version": "0.0.1",
"main": "dist/index.js",
"types": "dist/index.d.ts",
"files": [
"dist"
],
"scripts": {
"build": "rimraf dist && tsc",
"prepack": "npm run build"
},
"devDependencies": {
"rimraf": "^3.0.2",
"typescript": "^4.7.4"
},
"description": "description",
"author": {
"name": "name",
"email": "email"
}
}
Configuration settings in tsconfig.json:
{
"compilerOptions": {
"module": "commonjs",
"declaration": true,
"removeComments": true,
"target": "es2017",
"baseUrl": "./",
"skipLibCheck": true,
"outDir": "./dist"
}
}
Dry-run output of npm publish:
$ npm publish --dry-run
...
In case you require access to the project files or more information, feel free to reach out. Thank you for your attention.