Make it easy to synthesize objects typically created by the UA?

[RByers]

Often the 99% use case for an API involves the UA generating objects of a particular type (eg. MouseEvent). IMHO it's important to also support the 1% case where subject objects are created by script and are (mostly) indistinguishable from the UA-generated ones.

For example, a library/component designed just for MouseEvent could be driven via another component that consumes TouchEvents by synthesizing fake MouseEvent instances. Also this is often necessary to enable good unit testing of components.

Should the design principles say something about this?

[RByers]

Here's an example where @domenic says:

Having objects be constructed magically by the platform should be reserved for truly special cases. One example use case is mocking libraries.

[domenic]

I can take this. I have been dispensing opinions around constructors for a long time, and having it written down somewhere would be great. It's a bit subtle sometimes---see e.g. w3c/wot-scripting-api#3 where I came to the conclusion that there was too much UA magic for constructors to make sense---so this will be an interesting entry to write.

[RByers]

Great, looking forward to gleaning your wisdom!

[torgo]

@domenic you assigned yourself on this. Are you planning to submit a PR?

[domenic]

Somehow this fell off my to-do list. Let me bump it back up.

[dbaron]

Should this be merged with #44?

[dbaron]

Oh, except there's a PR for this in #80. :-)