bug#74963: Ambiguous treesit named and anonymous nodes in ruby-ts-mode

[Yuan Fu]

> On Dec 24, 2024, at 9:52 AM, Juri Linkov <juri@linkov.net> wrote:
> 
>> I’ll go with the (and named “unless”) route because after thinking
>> about it more, “(unless)” will be hard to work with because the string
>> predicate is actually a regexp.
> 
> Is it possible to mark all node names specified in treesit-thing-settings
> as named?
> 
> I just discovered a new problem:
> 
> 1. With typescript-ts-mode on the following snippet:
> 
> type NodeInfo =
>  | (BaseNode & {
>      subtypes: BaseNode[];
>    })
>  | (BaseNode & {
>      fields: { [name: string]: ChildNode };
>      children: ChildNode[];
>    });
> 
> You can move point inside "string" and type C-M-f or C-M-b.
> But point doesn't move.
> 
> This is because treesit-thing-settings defines a named node "string".
> But anonymous node has the same name "string":
> 
>           (index_signature [ name: (identifier) :
>            index_type: (predefined_type string)
> 
> and (treesit-node-at (point)) returns
> #<treesit-node "string" in 111-117>
> 
> This mismatched "string" in TypeScript is even more
> unexpected than "unless" in Ruby.
> 
> So probably we need a way to mark all used nodes as named
> to avoid such unexpected matches.  Maybe matching anonymous nodes
> should be opt-in, and by default match only named nodes.

IMHO this is just an unfortunate bug that needs to be fixed. I agree that this 
type of bug are hard to avoid, which is a bad thing, but that doesn’t mean we 
should try to  alleviate it at any cost. Making predicates named by default 
just adds complexity and inflexibility for not much benefit.

Yuan