Run prettier from CLI with config in package.json

Question

I'm trying to run Prettier from CLI defining the config in the package.json file as it's explained in Offical Docs

Prettier uses cosmiconfig for configuration file support. This means you can configure prettier via (in order of precedence):

A "prettier" key in your package.json file.

Howewer, using the following command and the folling package.json file, I get the shown error:

Command:

prettier --config package.json ./src/basic-sample.js

package.json:

{
    "name": "prettier-getting-started",
    "version": "1.0.0",
    "description": "Prettier - Getting started",
    "main": "index.js",
    "scripts": {
        "test": "echo \"Error: no test specified\" && exit 1",
    },
    "keywords": [
        "prettier"
    ],
    "author": "Rafa Romero",
    "license": "ISC",
    "devDependencies": {
        "prettier": "2.0.4"
    },
    "prettier":{
        "singleQuote": true
      }
}

Result:

[error] Invalid configuration file `src/basic-sample.js`: JSON Error in /Users/rafaromero/prettier-sample/package.json:
[error] LinesAndColumns$1 is not a constructor

I would like to note that if a use a .prettierrc.js file with the same command it works

Answer 1

I ran into this error while using a .prettierrc.json file, and the problem was that the file was encoded in UTF-16LE, not UTF-8. Saving the file as UTF-8 fixed this for me.

The root cause of this issue was following the documentation that recommended echo {}> .prettierrc.json to create the file. On Windows powershell, this creates a UTF-16LE file, not a UTF-8 file.

More discussion can be found at this github issue

Answer 2

According to https://prettier.io/docs/en/configuration.html configuration in package.json has the highest precedence, so you should be able to call:

prettier ./src/basic-sample.js
or
prettier --write ./src/basic-sample.js

I'm doing this from within an package.json script, but that shouldn't make any difference.

Answer 3

I also got this error when I was creating an instruction video for Prettier in Windows. As Luke suggested, saving the .prettierrc.json as UTF-8 using notepad++ solved the issue. Rather than using the echo {}> .prettierrc.json in the command as suggested in the Prettier documentation, it would be better to just create the file using an editor or notepad if you are using Windows.

NodeJS Drills - Running prettier and formatting code through the command line