Fix #882, variable input type mismatch throws AssertException

[tinnou]

Description

Added a null check in getTypeFromAST, similarly to what graphql-js does:
They return void (undefined in js) or the type itself.

export function typeFromAST(schema, typeNode) {
  /* eslint-enable no-redeclare */
  let innerType;
  if (typeNode.kind === Kind.LIST_TYPE) {
    innerType = typeFromAST(schema, typeNode.type);
    return innerType && GraphQLList(innerType);
  }
  if (typeNode.kind === Kind.NON_NULL_TYPE) {
    innerType = typeFromAST(schema, typeNode.type);
    return innerType && GraphQLNonNull(innerType);
  }
  if (typeNode.kind === Kind.NAMED_TYPE) {
    return schema.getType(typeNode.name.value);
  }
  /* istanbul ignore next */
  throw new Error(`Unexpected type kind: ${(typeNode.kind: empty)}.`);
}

Testing

Added unit tests to cover this issue + bonus spec cases we missed earlier.

[bbakerman]

If you want to use $ in a groovy multi line string, then just use ''' quotes instead. No need for quoting the $

[tinnou]

oh neat I didn't know you could do that! Thanks for the merge by the way.