bug#58711: Treesit hangs when calling treesit-search-forward

[Yuan Fu <casouri@gmail.com>]

> On Oct 22, 2022, at 2:53 AM, Wilhelm Kirschbaum <wkirschbaum@gmail.com> wrote:
> 
> I am attempting to implement treesit for the current elixir-mode using the branch feature/trees-sitter. For implementing beginning-of-defun-function using treesit I am running into an issue where the Emacs will hang indefinitely. Using (setq-local treesit-defun-type-regexp (rx (or "call"))) yields the same result.
> 
> For the following node-at-point output
> 
> (do_block (call target: (identifier)))
> 
> with Elixir code
> 
> # foo.ex
> defmodule Foo do
>   <<point/cursor here>>def bar(), do: "bar"
> end
> 
> When I call `(treesit-search-forward-goto (rx (or "call")) 'start nil t)` the function `treesit-search-forward` seems to get stuck. 
> 
> Elixir does not strictly have a begin function, but can be determined as one of the following:
> ; * modules and protocols
> (call
>   target: (identifier) @ignore
>   (arguments (alias) @name)
>   (#match? @ignore "^(defmodule|defprotocol)$")) @definition.module
> 
> ; * functions/macros
> (call
>   target: (identifier) @ignore
>   (arguments
>     [
>       ; zero-arity functions with no parentheses
>       (identifier) @name
>       ; regular function clause
>       (call target: (identifier) @name)
>       ; function clause with a guard clause
>       (binary_operator
>         left: (call target: (identifier) @name)
>         operator: "when")
>     ])
>   (#match? @ignore "^(def|defp|defdelegate|defguard|defguardp|defmacro|defmacrop|defn|defnp)$")) @definition.function
> 
> The elixir tree sitter implementation is here: https://github.com/elixir-lang/tree-sitter-elixir
> 
> I lack the knowledge to further debug this or find a clean workaround, but I'm almost sure that treesit-search-forward should never hang. 

Thanks for reporting this. The way treesit-search-forward-goto works makes it very to have infinite loops. I revised the way it traverses the tree and now it should be impossible to fall into infinite loops.

Yuan