How do I properly create a deno task in order to run something something like npm:create-svelte?

[bzm3r]

Previous discussion here but I got no feedback there, so I'm bringing it over here.

Apparently, deno run is going out the window for certain things, but this is confusing me as a Deno beginner:

We've discussed this internally, and this is working as intended.

deno run always prioritizes running code, which means it first and foremost treats it's arguments as file paths. For example you also can not run a task named ./task.ts with deno run, as it will attempt to load that file. Only if a task does not look like a file path or module specifier will we attempt to look for tasks and run them.

Instead you should use deno task to run tasks like this (or better, rename your task!).

Hi! Thank you for your explanation.

I'm new to deno, and it's not really clear to me how deno task fits here because of how the docs explain deno task (emphasis mine):

deno task provides a cross-platform way to define and execute custom commands specific to a codebase.

Suppose I want to execute npm:create-svelte@latest. This is not a command specific to a codebase, and therefore "not a task"! It is a command meant to initialize a codebase.

Suppose I were to generalize a bit, and define a codebase to be "my home directory". Then, I guess I would put a deno.json file there, with something like? (not sure)

{
  "tasks": {
    "create-svelte": "deno run -A npm:create-svelte@latest"
  }
}

I am not sure about the above because setting up a deno.json just to do a deno run seems very circular...

...to the point where I did not expect it to work.

Yet it did! And when it did, I was surprised, and tried a bare deno run -A npm:create-svelte@latest....

...which also worked? Huh. I made sure I've enabled DENO_FUTURE:

> $env:DENO_FUTURE
1

So, why does this work now? I am using:

> deno --version
deno 1.46.3 (stable, release, x86_64-pc-windows-msvc)
v8 12.9.202.5-rusty
typescript 5.5.2

So...is deno task the recommended way to run something like npm:create-svelte or is deno run still the way to go?

[marvinhagemeister]

I think you're taking the task concept a bit too much to the extreme. If you want to fire a one-off command for npm:create-svelte@latest, then you should just do that by calling deno run -A npm:create-svelte@latest. Whilst you can also put this in a task, it would be kinda pointless.

The motivation behind tasks is to abstract common complex tasks that you need to run daily. A typical use case is that there is a dev task that spins up your app in development mode, sets up file watching and maybe does other work needed to launch your application. Let's use a made up example and pretend that this would be the command to launch your app in development mode:

deno run -A --watch-hmr my-app.ts

Now you could of course always type out the whole command by hand yourself. This gets very tedious though. You could put this in a shell file, but then have to deal with different developers using different shells and operating systems, which all have a different syntax. Windows has PowerShell, macOS has zsh and linux typically has bash or sometimes fish. It's not something you want to bother with as a developer, and neither should your team mates.

So what if you could just call deno taks dev instead? That way you don't need to remember the exact command for a project. Most projects have different commands for this and having to remember every one of them is annoying, especially if you're working in a team that works on many project at the same time.

We can solve this headache by adding a dev task to all projects. That way developers on the different projects don't need to remember whether this projects needs to copy some files first before launching, how to set up the file watcher for this particular project, what the entrypoint name for a certain project is, etc. The list of things to remember gets pretty long the more complex a project grows.

This all can be solved with tasks. Let's add a task for development setup of our imaginary project:

{
  "tasks": {
    "dev": "deno run -A --watch-hmr my-app.ts"
  }
}

This means now you can just call deno task dev and don't have to remember anything else. In other words: The task feature is only there fore convenience. It allows you to abstract away more complex commands in something that's easier to remember. In most projects you'll find a build, a start or a dev task respectively. As you discovered, they make no sense for one off things like bootstrapping a new project. That said, nothing prevents you from creating a task out of any deno command. You can literally put anything in a task. Whether that is a useful thing to do is a different question.