Execution and Publishinig

Before Running

To execute the command locally, whether for testing, prototyping, or just every day use without a package install, you first need to build the application from the Typescript code to JavaScript so that the node processor can handle the code properly. You can use any method of compilation you find preferable, Typescript’s tsc, @nestjs/cli’s build, esbuild, swc, webpack. Just make sure that the compiler understands and can handle decorators, and the output code is transpiled correctly.

Local Execution (Using Node)

Once the code is compiled, you can use node to kick off the command using

node ./dist/main [args] [options]

This does make use of the packages locally installed in the node_modules, but other than that there’s nothing fancy necessary.

Local Execution (Without Node explicitly)

You can also add a shebang to the top of your main.ts and make the file executable by using chmod, then just use

./dist/main [args] [options]

but this generally is not necessary to do.

Nest CLI

You can also use the Nest CLI to build and start the command. You can pass any arguments after --

nest start --watch -- [args]

Ts-Node

If you don’t feel like compiling the application every time you make a small change, or don’t want to set up a file watcher to watch for you, you can use ts-node to start up the command. Just like with the node variants, you just need to pass the main path to the command.

ts-node src/main.ts [args] [options]
# OR is ts-node is not installed globally
npx|yarn|pnpm ts-node src/main.ts [args] [options]

Packaging the CLI

The last option, and probably the most useful one, is using a package manager to distribute the CLI via an npm package. You can add a bin property to the package.json and give your CLI a name along with a path to the main file and on installation npm will set up the path in the node_modules/.bin if a local install or $(npm prefix -g)/bin for a global package install.

Important note from npmjs documentation (link):

Please make sure that your file(s) referenced in bin starts with #!/usr/bin/env node, otherwise the scripts are started without the node executable!

If we take the crun application we’ve made so far, we can set up the package.json like so:

{
  "name": "crun",
  "description": "A command line runner using nest-commander",
  "bin": {
    "crun": "dist/main.js"
  },
  "scripts": {
    "build": "nest build"
  },
  "dependencies": {
    "@nestjs/common": "^7.0.0",
    "@nestjs/core": "^7.0.0",
    "nest-commander": "^1.2.0"
  },
  "devDependencies": {
    "@nestjs/cli": "^7.0.0",
    "@nestjs/schematics": "^7.0.0",
    "@nestjs/testing": "^7.0.0",
    "jest": "^26.0.0",
    "nest-commander-schematics": "^1.1.0",
    "nest-commander-testing": "^1.1.0",
    "typescript": "^4.3.0"
  }
}

Now if we were to publish this package and someone were to install it, the crun command would be available either globally via a global install, so crun could be used on the command line directly, or locally via a local install, so crun could be used in a package.json script or using npx/yarn/pnpm.