[0.57] [Android] DatePickerAndroid doesn't open because of null minDate

[MaxInMoon]

Environment

  React Native Environment Info:
    System:
      OS: macOS High Sierra 10.13.6
      CPU: x64 Intel(R) Core(TM) i5-5257U CPU @ 2.70GHz
      Memory: 55.30 MB / 8.00 GB
      Shell: 3.2.57 - /bin/bash
    Binaries:
      Node: 10.10.0 - /usr/local/bin/node
      Yarn: 1.9.4 - /usr/local/bin/yarn
      npm: 6.4.1 - /usr/local/bin/npm
      Watchman: 4.9.0 - /usr/local/bin/watchman
    SDKs:
      iOS SDK:
        Platforms: iOS 11.4, macOS 10.13, tvOS 11.4, watchOS 4.3
    IDEs:
      Android Studio: 3.0 AI-171.4443003
      Xcode: 9.4.1/9F2000 - /usr/bin/xcodebuild
    npmPackages:
      react: ^16.5.1 => 16.5.1 
      react-native: ^0.57.0 => 0.57.0 
    npmGlobalPackages:
      react-native-cli: 2.0.1
      react-native-git-upgrade: 0.2.7

Description

Problem: when no minDate is provided, the DatePickerAndroid won't open because of this error:

Cannot read property 'getMonth' of null

For info, I use react-native-modal-datetime-picker, itself using DatePickerAndroid.

Cause

See the _toMillis function below.

function _toMillis(options: Object, key: string) {
  const dateVal = options[key];
  // Is it a Date object?
  if (typeof dateVal === 'object' && typeof dateVal.getMonth === 'function') {
    options[key] = dateVal.getTime();
  }
}

if (typeof dateVal === 'object' && typeof dateVal.getMonth === 'function') doesn't block when dateVal is null. Cause typeof null is object (wtf!?)

Reproducible Demo

I can provide a reproducible demo, but I want first to have your opinion about the issue I described above.

Thank you

[RSNara]

Nice catch! This looks like a bug with _toMillis. Looks like we need to use something similar to _.isObjectLike here.

Would you like to launch a PR to fix this? If so, feel free to add me as a reviewer.