refactor(parser): Invert event processing

[fb55]

See #403 for details.

The parser currently first checks the insertion mode, and then the token type. By inverting this (checking first the token type, then the insertion mode), we prepare the parser to accept the events from #404.

This change also allowed foreign content checks to be greatly simplified.

[fb55]

One thing I am currently unhappy about is the tokenizer.inForeignNode and currentNotInHTML naming inside of the parser.

• currentNotInHTML indicates that the current node is not an element in the HTML namespace.
• tokenizer.inForeignNode (fka. tokenizer.allowCDATA) indicates that the current node is not an element in the HTML namespace, and that it is not an integration point for either MathML or HTML. (See https://html.spec.whatwg.org/#tree-construction)

If someone can come up with better names, I'm am more than happy to take them.

[wooorm]

Isn’t this a deviation from how the spec is written? Seems like that’ll cause future problems.

[fb55]

Isn’t this a deviation from how the spec is written? Seems like that’ll cause future problems.

parse5 already has a split for specific token handlers that doesn't exist in the spec. The splitting point was moved up by a step, which shouldn't make it harder to map the spec to the code.