How to run a command automatically in VS Code when you open a project

19 Oct 2020

4 min read

Sometimes, I trip myself up by forgetting to run Webpack when I open a JavaScript project. Usually it’s when I’m groggy in the morning and I get to a point where I expect some output to have changed, and nothing is happening. It takes me a minute to orientate myself and have that doh! moment, and realise that I haven’t spun up webpack yet. 🤦‍♂️

So, to spare myself this ignominy again, it would be great to have webpack launch when I open a JavaScript project that uses webpack.

VS Code has tasks built-in for this very thing. You can check out the Tasks User Guide for the full skinny. I will just show you to tackle my use case.

I want to execute one of my npm scripts from my package.json. From the command-line, I run npm run webpack. You can run whatever command you wish as a task.

JSON

{
  "scripts":{
    "webpack":"webpack --mode development --watch"
  }
}

TLDR

Add the following task to the workspace tasks.json.

JSON

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "Run npm webpack on startup",
      "type": "shell",
      "command": "npm run webpack",
      "windows": {
        "command": "npm run webpack"
      },
      "presentation": {
        "reveal": "always",
        "panel": "new"
      },
      "runOptions": { "runOn": "folderOpen" }
    }
  ]
}

Enable automatic tasks yourself by running the command Tasks: Allow Automatic Tasks in Folder.

How to create a task file

The tasks specific to your project are stored in <project folder>/.vscode/tasks.json. You can create the file yourself, or you can run the Tasks: Configure Task command to build a template file for you.

The command asks you a couple of questions before creating the file.

Select a task to configure: You can skip this and hit Enter.
Select a task template: Select the “Others” option.

This is the skeleton tasks.json that you get.

JSON

{
	"version": "2.0.0",
	"tasks": [
		{
			"label": "echo",
			"type": "shell",
			"command": "echo Hello"
		}
	]
}

How to create a task

So, we want to add a new task object like “echo” above. There is Intellisense support to assist you, so you can press Ctrl+Space to get a list of the properties.

Here is a list of the most important task properties:

label: The label used in the user interface.
type: For a custom task, this can either be shell or process. If shell is specified, the command is interpreted as a shell command e.g. bash, cmd. If process is specified, the command is interpreted as a process to execute. We want to select shell.
command: The actual command to execute. We want to execute npm run webpack.
windows: Windows specific properties. This will be used instead of the default properties when the command is executed on the Windows operating system. This also has a command property, I don’t know if it is necessary to specify your command in here again if you are Windows user. I guess it depends on your particular command. I added it anyway.
presentation: This defines how the task output is handled in the terminal. It offers the following properties:
- reveal: Controls whether the Integrated Terminal panel is brought to front. Valid values are:
  - always - The panel is always brought to front. This is the default. I prefer to see the command running on startup, so this option is what I want!
  - never - The user must explicitly bring the terminal panel to the front themselves.
  - silent - The terminal panel is brought to front only if the output is not scanned for errors and warnings.
- panel: Controls whether the terminal instance is shared between task runs. Valid values are:
  - shared: The terminal is shared and the output of other task runs are added to the same terminal.
  - dedicated: The terminal is dedicated to a specific task. If that task is executed again, the terminal is reused. However, the output of a different task is presented in a different terminal.
  - new: Every execution of that task is using a new clean terminal. A clean panel is preferable. Check this!
runOptions: Defines when and how a task is run. It has the property:
- runOn: Specifies when a task is run. Valid values are:
  - default: The task will only be run when executed through the Run Task command.
  - folderOpen: The task will be run when the containing folder is opened. This is what we want!

This is what did the trick for me:

JSON

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "Run npm webpack on startup",
      "type": "shell",
      "command": "npm run webpack",
      "windows": {
        "command": "npm run webpack"
      },
      "presentation": {
        "reveal": "always",
        "panel": "new"
      },
      "runOptions": { "runOn": "folderOpen" }
    }
  ]
}

The first time you open a project that contains a task that runs on “folderOpen”, you should get a prompt asking if you want to allow tasks to run automatically in that folder. I didn’t get this prompt!

You can enable automatic tasks yourself by running the command Tasks: Allow Automatic Tasks in Folder.

The result

Next time you open your project, you will see your task running automatically like so:

demonstration of task running on startup in integrated terminal

Hurrah! One less thing to think about! 😅

Tagged

vscode