Create a Single-Command Node.js CLI with Oclif, TypeScript and Yarn Workspaces

Instructor: [0:00] Start with an empty folder. You can scaffold a new oclif command with npx oclif. We'll choose a single command for now. We'll name it mycli. Oclif gives you a few prompts, most of which you can just use the defaults. Feel free to customize if you wish.

[0:26] Once you're done installing and scaffolding out, you'll have a new folder called mycli, which contains your new CLI. This is all the required fields for a Node CLI like a bin field on your package.json as well as the shebang that you might want to execute a script from.

[0:47] Then the rest of it dives into the oclif framework specifically. Over here, we're just running a single index.ts file. That just runs the oclif framework for you. To execute this CLI locally, you could CD into a new directory and then run that new file with bin/run.

[1:12] That would give you the basic hello world message that is scaffolded from within the oclif app, but this isn't exactly how your user would run your CLI. They would actually run your CLI like mycli and expect something to be able to run.

[1:30] There are two ways to simulate this locally. You can actually yarn link global, or you can use a yarn workspace. For this lesson, we're going to use a yarn workspace because it's the more advanced use case and it's a little bit harder to set up.

[1:47] I'm going to create a separate folder called packages. Then I'm going to use my finder window to move mycli into the packages. This is to prevent VS Code from renaming everything inside of it.

[2:04] To enable the workspace, I need to define a package.json. Inside of it, I need to set two fields. The first field is the private field. I need to set that to true. The second field is the workspace's field. I need to tell yarn what packages folder I'm using.

[2:28] That should be sufficient for installing these workspaces. We can go ahead and run yarn. Now yarn is aware of this mycli package. For example, I can run yarn mycli and get back the same result.

[2:51] The reason you might want to use a yarn workspace is in case you have an example demo package, for example. You can just add that example folder over here. Inside of this example demo project, which you can fill out over here, you can use the CLI from within the packages folder as though it was an installed binary but still edit the code and see it run live, which is very nice.

[3:23] Over here, I can run yarn workspace example. I do need to define the package.json as well. Over here, I can run name example. Then I can run yarn workspace example, which chooses the example workspace. Then within that context of the example workspace, I can run mycli within it.