Native support for else and else if in block statements

[mogstad]

As there isn't a native concept of if statements in the grammar, it makes it especially hard to query else if statements, as they've previously just been exposed as a helper. It makes it cumbersome to query else blocks and not possible—I think at least—to query and capture else if as the same capture.

else is supported for all block_statements in Ember, but else if isn't, but it wouldn't be valid syntax that we want to capture any other way, so I haven't tried to be cleaver about it.

I’m unsure if this is the way to solve, but I don’t think it’s unreasonable to have “native” support for it.

[NullVoxPopuli]

sorry it took so long to see this PR! :(

what is the motivation for this change? I'm not sure I understand

[mogstad]

The motivation is to move the burden of selecting "else" and "else if" in block statements from queries, to the parser, and treat else and else if a first class concepts (as block_statement_inverse). Querying else if is today rather compiled.

To query else you can do: (which is complicated, but fine, and is equal to if)

(mustache_statement
	(identifier) @keyword
	(#eq? @keyword "else"))

But "else if" on the other hand: I wasn't able to implement in Zed, so I don't have the actual query but conceptually its query needs to be:

• A helper_invocation
  • with a helper: that is an identifier that equals else.
  • its first argument: is an identifier that equals if.
  • (ideally we ensure it has another argument)

Conceptually this doesn't match what we expect. I don't think of else if as a helper named else with its first argument the identifier if.

If's are still kept as mustache_statement and an identifier as it needs to support many keywords (each, each-in, ...), but the inverse is always else (and else if for ifs.)

TLDR I want my else if's to syntax highlighted correctly:

[NullVoxPopuli]

Tyty. Seems ok to me