Schematics is a one of the famous generator tool. It’s using in Angular / NestJS / and any other big project.

If we want to create CLI tool with generator, we want to use Schematics within.

So, in this posts, I try to execute schematics generator from CLI tool.

Step1: Setup CLI project by oclif

First, setup the example CLI project.

Today, I used oclif.

$ npx oclif single schematics-cli
$ cd schematics-cli

After the setting up, we can see the default message to execute the following command.

$ ./bin/run 
hello world from ./src/index.ts

Step2: Install schematics-cli

Next, install schematics cli library.

We’ll execute the schematics by using it.

$ yarn add @angular-devkit/schematics-cli

Step3: Add schematics project

In this post, use NestJS project

$ yarn add @nestjs/schematics

Of course, we can use own schematics or local schematics.

Execute schematics-cli from oclif

The generating process starts from the main() function in the CLI library.

So the following code is calling the function directly.

import {Command} from '@oclif/command'
import {
  main
} from "@angular-devkit/schematics-cli/bin/schematics"

class SchematicsCli extends Command {
  static description = 'describe the command here'

  async run() {
    await main({
      args: [
          "@nestjs/schematics:interface",
          "--name=helloOclif"
      ]
  })
  }
}

export = SchematicsCli

The function property is the same as the schematics CLI args.

Execute

Finally, execute CLI command made by oclif.

We can get a new class file for NestJS.

% ./bin/run
CREATE src/hello-oclif.interface.ts (31 bytes)

$ cat ./src/hello-oclif.interface.ts
export interface HelloOclif {}

Conclusion

We can easy to execute schematics-cli task from own script.

So if we want to create own CLI tools with any generator, we can use Schematics.

[Appendix] Execute public schematics from schematics-cli

Almost schematics project can use from their own CLI tools, like angular-cli / nest-cli / etc.

But we can use these schematics from schematics-cli

$ npm init -y
$ npm i -D @angular-devkit/schematics-cli
$ npm i -S @nestjs/schematics
$ ./node_modules/.bin/schematics @nestjs/schematics:interface --name test
CREATE src/test.interface.ts (25 bytes)