Universal File Watcher

Run any external tool on file save and see its output as inline diagnostics — directly in the editor, no tool-specific plugin required.

Inspired by PyCharm's File Watchers, this extension is a thin, generic bridge between VS Code and any command-line linter, type checker, formatter, or custom script.

Features

Quick Start

1 — Install the extension

git clone https://github.com/VictorMalyshkin/vscode-universal-file-watcher
cd vscode-universal-file-watcher
npm install
npm run compile
# Press F5 in VS Code to open an Extension Development Host

2 — Add a watcher to your project

Open .vscode/settings.json (create it if it doesn't exist) and add:

{
  "universalFileWatcher.watchers": [
    {
      "name": "mypy",
      "filePattern": "**/*.py",
      "command": "mypy --show-column-numbers --no-error-summary ${file}",
      "outputPattern": "^(?<file>[^:]+):(?<line>\\d+):(?<col>\\d+): (?<severity>error|warning|note): (?<message>.+)$"
    }
  ]
}

Save any .py file — mypy runs, and its output appears as diagnostics in the Problems panel and as squiggles in the editor.

Configuration Reference

All settings live under the universalFileWatcher namespace.

universalFileWatcher.watchers (array)

The heart of the extension. Each element is a watcher object.

Required watcher fields

Optional watcher fields

Other settings

Variables

The following variables are expanded in command and cwd:

Named Capture Groups

The outputPattern regex must use named capture groups ((?<name>...)).

Supported group names

applyTo

Use savedFile when the tool only checks one file at a time (mypy ${file}). Use matchedFile when the tool checks the whole project and reports many files (tsc --noEmit, cargo check).

Examples

Python — mypy

{
  "name": "mypy",
  "filePattern": "**/*.py",
  "command": "mypy --show-column-numbers --no-error-summary ${file}",
  "outputPattern": "^(?<file>[^:]+):(?<line>\\d+):(?<col>\\d+): (?<severity>error|warning): (?<message>.+?)(?:\\s+\\[(?<code>[a-z-]+)\\])?$",
  "continuationPattern": "^(?<file>[^:]+):(?<line>\\d+):(?<col>\\d+): note: (?<message>.+)$",
  "codeUrl": "https://mypy.readthedocs.io/en/stable/error_codes.html#code-${code}",
  "ignoreExitCodes": [1]
}

Python — flake8

{
  "name": "flake8",
  "filePattern": "**/*.py",
  "command": "flake8 ${file}",
  "outputPattern": "^(?<file>[^:]+):(?<line>\\d+):(?<col>\\d+): (?<code>[A-Z]\\d+) (?<message>.+)$",
  "severity": "warning"
}

Python — ruff

{
  "name": "ruff",
  "filePattern": "**/*.py",
  "command": "ruff check --output-format=text ${file}",
  "outputPattern": "^(?<file>[^:]+):(?<line>\\d+):(?<col>\\d+): (?<code>[A-Z]\\d+) (?<message>.+)$",
  "severity": "warning",
  "codeUrl": "https://docs.astral.sh/ruff/rules/${code}",
  "ignoreExitCodes": [1]
}

TypeScript — tsc (whole project)

{
  "name": "tsc",
  "filePattern": ["**/*.ts", "**/*.tsx"],
  "command": "npx tsc --noEmit --pretty false",
  "outputPattern": "^(?<file>[^(]+)\\((?<line>\\d+),(?<col>\\d+)\\): (?<severity>error|warning) TS(?<code>\\d+): (?<message>.+)$",
  "cwd": "${workspaceFolder}",
  "applyTo": "matchedFile"
}

JavaScript/TypeScript — ESLint

{
  "name": "eslint",
  "filePattern": ["**/*.js", "**/*.ts", "**/*.jsx", "**/*.tsx"],
  "command": "npx eslint --format=unix ${file}",
  "outputPattern": "^(?<file>[^:]+):(?<line>\\d+):(?<col>\\d+): (?<message>.+) \\[(?<severity>Error|Warning)/(?<code>.+)\\]$",
  "severity": "warning",
  "codeUrl": "https://eslint.org/docs/rules/${code}",
  "ignoreExitCodes": [1]
}

Rust — cargo check

{
  "name": "cargo check",
  "filePattern": "**/*.rs",
  "command": "cargo check --message-format=short 2>&1",
  "outputPattern": "^(?<file>[^:]+):(?<line>\\d+):(?<col>\\d+): (?<severity>error|warning)(?:\\[(?<code>[^\\]]+)\\])?: (?<message>.+)$",
  "cwd": "${workspaceFolder}",
  "applyTo": "matchedFile"
}

Shell — shellcheck

{
  "name": "shellcheck",
  "filePattern": ["**/*.sh", "**/*.bash"],
  "command": "shellcheck -f gcc ${file}",
  "outputPattern": "^(?<file>[^:]+):(?<line>\\d+):(?<col>\\d+): (?<severity>error|warning|note): (?<message>.+?) \\[(?<code>SC\\d+)\\]$",
  "severity": "warning",
  "codeUrl": "https://www.shellcheck.net/wiki/${code}"
}

Custom script

{
  "name": "my-checker",
  "filePattern": "**/*.py",
  "command": "python ${workspaceFolder}/scripts/check.py ${file}",
  "outputPattern": "^(?<file>[^:]+):(?<line>\\d+):(?<col>\\d+): (?<severity>error|warning): (?<message>.+)$",
  "cwd": "${workspaceFolder}",
  "env": {
    "MY_API_KEY": "...",
    "PYTHONPATH": "${workspaceFolder}/src"
  }
}

More examples are in the examples/ directory.

Commands

Open the Command Palette (Ctrl+Shift+P / Cmd+Shift+P):

Development

Prerequisites

• Node.js 20+
• VS Code 1.85+

Setup

git clone https://github.com/VictorMalyshkin/vscode-universal-file-watcher
cd vscode-universal-file-watcher
npm install

Compile and run

npm run compile    # one-time build
npm run watch      # watch mode (recompiles on change)

Press F5 in VS Code to open an Extension Development Host with the extension loaded.

Lint

npm run lint

Package as .vsix

npm run package
# produces universal-file-watcher-1.0.0.vsix

Install locally:

code --install-extension universal-file-watcher-1.0.0.vsix

Troubleshooting

No diagnostics appear

1. Open File Watcher: Show Output Channel and check the raw output.
2. Verify the command runs correctly in your terminal with the exact file path.
3. Check that outputPattern matches your tool's actual output format — test in regex101.com with the ECMAScript flavor.
4. Make sure filePattern matches the file you saved (e.g., **/*.py requires the path to end in .py).

Command not found

• Set "runInShell": true (default) so the shell PATH is inherited.
• Or use the full path: "command": "/usr/local/bin/mypy ${file}".
• For virtualenv/conda: prefix the command, e.g. "command": "source .venv/bin/activate && mypy ${file}".

Diagnostics on wrong file

• If the tool checks the whole project (e.g., tsc --noEmit), set "applyTo": "matchedFile" and make sure the file capture group is in your regex.
• If the tool only checks one file, use "applyTo": "savedFile" (default).

Too slow / running too often

• Increase universalFileWatcher.debounceMs (default 300 ms).
• Disable watchers you don't need with "enabled": false.

Contributing

Pull requests and issues are welcome. Please open an issue first for significant changes.

License

MIT