Do not silently ignore package.json in zeit deployment

[oroce]

What kind of change does this PR introduce?
Fix

What is the current behavior?

If you omit the files entry in your now.json then the deployment works without any issues but if you customize the now.files and you happen to have package.json in that list, it will be ignored from the deployment. If the package.json is omitted then zeit won't install the required dependencies.

Example configuration:

now.json

{
  "version": 2,
  "files": [
      "index.js",
      "package.json"
   ],
   "builds": [{
      "src": "index.js",
      "use": "@now/node"
    }]
}

package.json

{
  "dependencies": {
       "express": "4.16.4"
   }
}

index.js

require('express');

The deployment of a sandbox with the configuration above will be successful but when you are trying to open your deployment it'll crash with an error of 500. (MODULE_NOT_FOUND)

What is the new behavior?

If the user add package.json to the now.files it'll be included.

Checklist:

• Documentation N/A
• Tests - need help here
• Ready to be merged
• Added myself to contributors table (see additional parameters to zeit deployment #1542)

I found this issue while I was building a Pusher authentication server using zeit for a sample vue chat app. I had to define the now.files since the sandbox has lots of files (config, static, build, etc) which should be deployed to zeit (and cannot be due to some zeit errors). For now, I moved the server to a different sandbox and deployed from there.

[SaraVieira]

Thank you for fixing this!

[ValentinFunk]

Has this perhaps caused an issue? For me I always get an error with duplicate files when uploading to Zeit:

{"error":{"code":"invalid_files","message":"One or more file definitions contain errors in them","errors":[{"reason":"duplicated_file_path","path":"package.json"}]}}

There are two package.json in the request when uploading with this now.json:

{
  "version": 2,
  "name": "my-react-app",
  "builds": [
    {
      "src": "package.json",
      "use": "@now/static-build",
      "config": {
        "distDir": "build"
      }
    }
  ],
  "routes": [
    {
      "src": "^/static/(.*)",
      "headers": {
        "cache-control": "s-maxage=31536000,immutable"
      },
      "dest": "/static/$1"
    },
    {
      "src": "^/favicon.ico",
      "dest": "/favicon.ico"
    },
    {
      "src": "^/asset-manifest.json",
      "dest": "/asset-manifest.json"
    },
    {
      "src": "^/manifest.json",
      "dest": "/manifest.json"
    },
    {
      "src": "^/precache-manifest.(.*)",
      "dest": "/precache-manifest.$1"
    },
    {
      "src": "^/service-worker.js",
      "headers": {
        "cache-control": "s-maxage=0"
      },
      "dest": "/service-worker.js"
    },
    {
      "src": "^/(.*)",
      "headers": {
        "cache-control": "s-maxage=0"
      },
      "dest": "/index.html"
    }
  ]
}