kongyo-ts-prettier-setup

name: kongyo-ts-prettier-setup description: Set up Prettier code formatter for TypeScript npm projects with merge-safe defaults.

kongyo-ts-prettier-setup

Set up Prettier for an existing or new TypeScript npm project.

Merge rules for existing projects:

• Do not overwrite existing scripts or ignore entries blindly.
• Add missing entries; keep existing behavior unless explicitly requested to replace.

Target Project Scope

• Single package repo: edit the root package.json.
• Monorepo: edit the package.json in the workspace/package the user asked for.
• If the target package is not explicit, ask which workspace/package to update before editing.

Installation

npm install -D prettier

If prettier is already in devDependencies, do not reinstall by default. Reinstall or upgrade only when the user asks to pin/change the version.

Configuration Files

Create .prettierrc.json if it does not exist:

{
  "semi": true
}

If .prettierrc.* already exists, keep it as-is by default. Only change existing Prettier options when at least one is true:

• The user explicitly requested a style change.
• A team/project style guide requires it.
• The current config is invalid JSON/YAML/TOML and must be fixed.

Create .prettierignore if it does not exist:

node_modules
dist
coverage
*.min.js
package-lock.json

If .prettierignore already exists, append only missing lines from the list above.

Package.json Scripts

If format does not exist:

{
  "scripts": {
    "format": "prettier --write .",
    "format:check": "prettier --check .",
    "check:file": "prettier --check"
  }
}

If format already exists for another formatter, keep it and add format:prettier instead:

{
  "scripts": {
    "format": "<keep existing>",
    "format:prettier": "prettier --write .",
    "format:check": "prettier --check .",
    "check:file": "prettier --check"
  }
}

Usage

Run full formatting:

• npm run format (or npm run format:prettier when format is already used)

Run repository check:

• npm run format:check

Run a single file check:

• npm run check:file -- src/index.ts

Verification Notes

• If package.json already declares prettier but node_modules is not installed yet, run npm install before format:check / check:file.
• For check:file, pass an existing file path in the target package (for example src/index.ts or another tracked file).