namespaces: validate and extract uses the strictly split a string in a vague manner

[dlrobertson]

Namespaces validate and extract uses strictly split a string in the following step:

5. If qualifiedName contains a U+003A (:), then strictly split the string on it and set prefix to the part before and localName to the part after.

strictly-split defines the result as a list, so "the part before" and "the part after" feels a bit vague. Due to the validation in step two and the branch condition the list will have two elements, but it would be a bit clearer to use list indexing.

[dlrobertson]

To what extent is it helpful to be explicit about things? When thinking about a step like this, I tend to think of something like:

5. If qualifiedName contains a U+003A (:), then run the following steps:
   1. Let splitResult be the result of strictly split given qualifiedName and U+003A (:).
   2. Set prefix to splitResult[0].
   3. Set localName to splitResult[1].

Unwrapping things like this feels a bit verbose. Is there a better way?

[annevk]

You can leave out " run the following steps".

@domenic did we start using

Let [prefix, localName] be the result of ...

already?

Even without that though your version is clearer and I'd definitely support moving to that.

[domenic]

We've been doing it as "Let (prefix, localName) be the result of..." but only for tuples, not lists. (And it's not documented anywhere.)