Treat unknown opt types as Object in ol externs

[elemoine]

As discussed previously we want to export base classes. This is to be able to do, for example, source instanceof ol.style.Image in applications. Exporting base classes means marking them with the @api annotation.

The problem is that, currently, if we just add the @api annotation to the base class we get an unknown type for that class' options type in the ol externs file:

/**
 * @constructor
 * @param {ol.style.ImageOptions} options
 */
ol.style.Image = function(options) {};

where ol.style.ImageOptions is not declared in the ol externs file.

One option involves adding @api to the options @typedef as well. This indeed fixes the problem in the ol externs file. But this creates a broken link in the API doc. In any way, it does not make sense to add @api to the options @typedef, because abstract base classes are not meant to be instantiated by applications.

This PR fixes the problem by making the generate-externs.js script use @typedef {Object} in the generated externs file for options types that are referenced in "exported" constructors but not marked with an @api annotation.

I have to admit that the code added to generate-externs.js is not of the prettiest, but I haven't been able to come up with a prettier solution.

Thanks for any review.

[gberaudo]

+1 for this simple implementation.

Not having the option typedefs in olx for these particular cases make sense to me.
Indeed, only application code compiled together with ol3 may have a use of these options.

The reason, is that minification prevents base methods to be overridden by non-compiled code.

[elemoine]

Options from olx namespace should not be automatically fixed as it is an error to not have a definition for them.

True. Changing…

[ahocevar]

Looks safe to me. Please merge.