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

[Yuan Fu]

> On Oct 22, 2022, at 11:42 PM, Yuan Fu <casouri@gmail.com> wrote:
> 
> 
> 
>> 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

Just a heads up: I changed the function signature of 
treesit-search-forward-goto in the latest commit.

Yuan