How to ignore some nodes?

[numToStr]

Hi 👋🏻,

Considering the following Lua code, I just wanted to only pick the lines that start with a comment (ie. ---) or function (ie. function). And ignore any other nodes/lines and even trailing comments.

local U = {} ---Ignore until eol

---@class CMode Comment modes - Can be manual or computed in operator-pending phase
---@field toggle number Toggle action
---@field comment number Comment action
---@field uncomment number Uncomment action
---@see VMode
---@see Mee
print("ignore this")
print("and this")

---Takes out the leading indent from lines
---@param str string
---@return string string Indent chars
---@return number string Length of the indent chars
---@see VMode
---@see Mee
function U.grab_indent(str)
	local _, len, indent = str:find("^(%s*)")
	return indent, len
end

return U

So I came up with the following where I ignore the useless nodes using None and pick others with Some.

use chumsky::{
    prelude::{choice, filter, just, take_until, Simple},
    text::{self, newline, TextParser},
    Parser,
};

#[derive(Debug)]
pub struct Lua;

impl Lua {
    pub fn parse(src: &str) -> Result<Vec<Option<String>>, Vec<Simple<char>>> {
        let node = choice((
            just("---")
                .then(filter(|c| *c != '\n').repeated().collect::<String>())
                .map(|(s, x)| format!("{s}{x}")),
            text::keyword("function")
                .ignore_then(filter(|x| *x != '(').repeated().collect().padded()),
        ))
        .map(Some);

        let misc = text::ident().then_ignore(take_until(newline())).to(None);

        choice((node.padded(), misc))
            .repeated()
            .collect()
            .parse(src)
    }
}

NOTE: With functions, I am only interested in the name.

---

So I am wondering Is there a nicer way to do this? Like, remove the Option<String> step and just return the useful nodes with Vec<String>?

[numToStr]

It seems I was on the right path and just missing the .flatten() combinator at the end. I am not sure whether this is correct or not, but I got the result that I wanted. Here is the new code

use chumsky::{
    prelude::{any, choice, filter, just, take_until, Simple},
    text::{self, newline, TextParser},
    Parser,
};

#[derive(Debug)]
pub struct Lua;

impl Lua {
    pub fn parse(src: &str) -> Result<Vec<String>, Vec<Simple<char>>> {
        let node = choice((
            just("---")
                .then(filter(|c| *c != '\n').repeated().collect::<String>())
                .map(|(s, x)| format!("{s}{x}")),
            text::keyword("function")
                .ignore_then(filter(|x| *x != '(').repeated().collect().padded()),
        ))
        .map(Some);

        let misc = any().then(take_until(newline())).to(None);

        choice((node.padded(), misc))
            .repeated()
            .flatten() // I was missing this
            .parse(src)
    }
}

[zesterer]

Looks about right, happy to hear you solved this!