Auto run command from vscode extension on file save

There is no default support for running Tasks, or Commands, on save (onSave). However, there is 3rd party support via the VSCode extension "Run on Save".

Here is the link: https://marketplace.visualstudio.com/items?itemName=emeraldwalk.RunOnSave

This is a very popular extension, I used it once a while back and it worked well for my use-case.

Also if you just want to lint, or format code, on save that can be done through VSCode settings.

EDIT June 20th 9:04pm UTC

If you want to add the command to your settings you have to configure a the extension, which is explained in the extensions README.md, that can be viewed by clicking on the extensions icon in the VSCode extensions explorer.

Configuration

Add "emeraldwalk.runonsave" configuration to user or workspace settings.

• "shell" - (optional) shell path to be used with child_process.exec options that runs commands.
• "autoClearConsole" - (optional) clear VSCode output console every time commands run. Defaults to false.
• "commands" - array of commands that will be run whenever a file is saved.
  • "match" - a regex for matching which files to run commands on

  NOTE Since this is a Regex, and also in a JSON string backslashes have to be double escaped such as when targetting folders. e.g. "match": "some\\\\folder\\\\.*"

  • "cmd" - command to run. Can include parameters that will be replaced at runtime (see Placeholder Tokens section below).
  • "isAsync" (optional) - defaults to false. If true, next command will be run before this one finishes.

Sample Config

This sample configuration will run echo statements including the saved file path. In this sample, the first command is async, so the second command will get executed immediately even if first hasn't completed. Since the second isn't async, the third command won't execute until the second is complete.

"emeraldwalk.runonsave": {
    "commands": [
        {
            "match": ".*",
            "isAsync": true,
            "cmd": "echo 'I run for all files.'"
        },
        {
            "match": "\\.txt$",
            "cmd": "echo 'I am a .txt file ${file}.'"
        },
        {
            "match": "\\.js$",
            "cmd": "echo 'I am a .js file ${file}.'"
        },
        {
            "match": ".*",
            "cmd": "echo 'I am ${env.USERNAME}.'"
        }
    ]
}

Configuring a command to execute when you save, isn't going to be as simple as hitting [F1] to open the quick-input, and finding the extensions task that you want to run. You will have to follow the instructions, and when you get stuck, you might have to come back and ask a question about the issue you are experiencing, or google it however; if your a Linux user, or you have a lot of MS-Dos or Powershell experience, this will be pretty straight forward.

As I noted in a comment, there are a number of "run on save" extensions. Here is one that will run external commands, like those from an extension. And it seems to be more recent and better maintained than some.

Run It On

Sample setting:

"runItOn": {
    "commands": [
        {
            "match": ".*",
            "isShellCommand" : false,
            "cmd": "myExtension.amazingCommand"
        },
        {
            "match": "\\.txt$",
            "cmd": "echo 'Executed in the terminal: I am a .txt file ${file}.'"
        }
    ],
    "watchers": [
        {
            "match": "**/*.js",
            "cmd": "echo 'Changes detected on js files.'"
        }
    ]
}

myExtension.amazingCommand is what you are looking for.

If You want just format code, check that activated native editor settings instead of installing RunOnSave

Just a heads up to the provided answer:

If you are using Python, the Run on Save extension (and any tasks.json for that matter) in VSCode do not see (automatically recognize) any active virtual environments in your workspace.

All commands are run as if from a shell in the current working directory before your environment is activated. (If you think about it, thinks makes sense because it doesn't know what language/program you are going to run)

To run a python command on save from within the context of a virtual environment, first manually activate it:

"cmd": ".venv\\Scripts\\activate.bat && py -m your_script.py"

Otherwise, the global python installation is used.

If you are using a command from a 3rd party package (e.g. pyupgrade) and you don't have that installed in your global python, nothing gets run. Even worse, if you have multiple python installations and both have the package installed, the package that gets run is the one from your global python, which may not be what you want.