Can I make npm install follow a certain package.json format?

Question

When you install an npm package and use the --save, --save-dev or --save-optional options to write the package into your package.json file in the appropriate dependencies property, the entire file appears to be rewritten with 2-space indentation:

$ cat package.json
{
    "name": "my-package"
}

$ npm install --save another-package && cat package.json
{
  "name": "my-package",
  "dependencies": {
    "another-package": "~0.1.5"
  }
}

Is there any way to make npm follow the existing format, or to specifiy a custom format (e.g. 4-space indentation) for the package.json file?

I can't find anything in the npm options documentation.

Answer 1

After digging through the npm source, it unfortunately appears the answer to my question is definitely "no". When npm install is executed with one of the "save" options, the following happens:

fs.readFile(saveTarget, function (er, data) {
  try {
    data = JSON.parse(data.toString("utf8"))
  } catch (ex) {
    er = ex
  }
  // ...
  data = JSON.stringify(data, null, 2) + "\n"
  fs.writeFile(saveTarget, data, function (er) {
    cb(er, installed, tree, pretty)
  })
})

The important line is the call to JSON.stringify. When invoking stringify with the third argument, the returned string indentation is formatted with the specified number of spaces.

Since there is no way to customise the value used by npm internally, this behaviour is currently non-configurable.