Detect when a polyfill is missing

[kassens]

Should we add some simple basic detection for missing polyfills so we can provide a helpful error message instead of some "method x is undefined" errors deep in the stack? (Example: #681)

Not full feature detection, but maybe something basic as:

warning(
  Promise && Array.prototype.find,
  'Relay relies on polyfills for older browsers. Babel '
  'provides a good one: https://babeljs.io/docs/usage/polyfill/'
)

[josephsavona]

This is a great idea. Ship it! ;-)

[KyleAMathews]

👍 this would of saved me some debugging time this morning :)

[edvinerikson]

If this is something that we still want to do I'll be happy to hack on it.

if (process.env.NODE_ENV === 'development') {
  warning(
    -es6-features-here,
    'message here'
  );
}

Would something like that work and where should the check live? RelayPublic?

[josephsavona]

@edvinerikson the best place is Relay.js. The check should likely use if (__DEV__) { ... }, which i think we transform appropriately (probably easiest to just try that and see what it builds to).