Unexpected end of JSON input

[jrop]

First of all I love this utility, thanks for making!

I am getting the following error:

SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at getDependencyTree (/Users/me/.config/yarn/global/node_modules/cost-of-modules/lib/helpers.js:64:17)
    at Object.getRootDependencies (/Users/me/.config/yarn/global/node_modules/cost-of-modules/lib/helpers.js:73:26)
    at Object.<anonymous> (/Users/me/.config/yarn/global/node_modules/cost-of-modules/lib/index.js:26:32)
    at Module._compile (module.js:569:30)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:503:32)
    at tryModuleLoad (module.js:466:12)
    at Function.Module._load (module.js:458:3)
    at Function.Module.runMain (module.js:605:10)

My package.json is:

{
  "name": "gtest",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "devDependencies": {
    "gulp": "gulpjs/gulp#4.0",
    "gulp-cli": "^1.3.0"
  }
}

I am using npm 5.0.0, and I suspect that the issue relates to npm ls --json printing errors after printing the json (note that sync-exec channels both STDOUT and STDERR and returns the combination).

You should probably use:

const {spawnSync} = require('child_process')
const proc = spawnSync('npm', ['ls', '--json'])
console.log(JSON.parse(proc.stdout.toString()))
// ignore proc.stderr

Erroneous "JSON" output (note STDERR at end):

{
  "name": "gtest",
  "version": "1.0.0",
  "problems": [
    "invalid: gulp@4.0.0-alpha.2 /Users/me/Desktop/gtest/node_modules/gulp",
    "extraneous: glob-watcher@3.2.0 /Users/me/Desktop/gtest/node_modules/glob-watcher",
    "extraneous: undertaker@1.1.0 /Users/me/Desktop/gtest/node_modules/undertaker",
    "extraneous: vinyl-fs@2.4.4 /Users/me/Desktop/gtest/node_modules/vinyl-fs",
    "extraneous: node-pre-gyp@0.6.36 /Users/me/Desktop/gtest/node_modules/node-pre-gyp"
  ],
  "dependencies": {
    "...": "..."
  }
}
npm ERR! invalid: gulp@4.0.0-alpha.2 /Users/me/Desktop/gtest/node_modules/gulp
npm ERR! extraneous: glob-watcher@3.2.0 /Users/me/Desktop/gtest/node_modules/glob-watcher
npm ERR! extraneous: undertaker@1.1.0 /Users/me/Desktop/gtest/node_modules/undertaker
npm ERR! extraneous: vinyl-fs@2.4.4 /Users/me/Desktop/gtest/node_modules/vinyl-fs
npm ERR! extraneous: node-pre-gyp@0.6.36 /Users/me/Desktop/gtest/node_modules/node-pre-gyp

[siddharthkp]

Thanks, that's super useful!

I'll happily take a PR if you would like to submit

[jrop]

This is turning out to be more difficult than I first thought. In my particular case the npm process is exiting before flushing STDOUT, which means that NodeJS gets truncated output back from it. I haven't figured out a workaround for this yet. I am investigating seeing if it is possible to switch to read-package-tree to see if that gives all of the data your utility needs, but the problem with that is that is an asynchronous module, and your code is synchronous. Lots to investigate

[jrop]

This seems to be a bug with NPM.

According to NodeJS (nodejs/node/issues/9633) all of STDIO is async, and if the process exits before all the data is flushed, it will not be able to be ready from child_process.

In NPM's lib/utils/error-handler.js file, in exit(code, noLog) -> reallyExit(err) the process is exited explicitly with process.exit(code). If I change that line to process.exitCode = code, then I am able to read all of the child_process's STDOUT.

[denieler]

the same issue with npm 5.1.0

[tvvignesh]

Same issue on my end. Works well in one project, but throws unexpected end of json in another. Screenshot below.

[michaelfarrell76]

[JLarky]

I have the same issue with yarn as well (yarn list --json)