helix/helix-syntax/src/pretty_print.rs

use std::fmt;

use tree_sitter::{Node, TreeCursor};

pub fn pretty_print_tree<W: fmt::Write>(fmt: &mut W, node: Node) -> fmt::Result {
    if node.child_count() == 0 {
        if node_is_visible(&node) {
            write!(fmt, "({})", node.kind())
        } else {
            write!(fmt, "\"{}\"", node.kind())
        }
    } else {
        pretty_print_tree_impl(fmt, &mut node.walk(), 0)
    }
}

fn pretty_print_tree_impl<W: fmt::Write>(
    fmt: &mut W,
    cursor: &mut TreeCursor,
    depth: usize,
) -> fmt::Result {
    let node = cursor.node();
    let visible = node_is_visible(&node);

    if visible {
        let indentation_columns = depth * 2;
        write!(fmt, "{:indentation_columns$}", "")?;

        if let Some(field_name) = cursor.field_name() {
            write!(fmt, "{}: ", field_name)?;
        }

        write!(fmt, "({}", node.kind())?;
    }

    // Handle children.
    if cursor.goto_first_child() {
        loop {
            if node_is_visible(&cursor.node()) {
                fmt.write_char('\n')?;
            }

            pretty_print_tree_impl(fmt, cursor, depth + 1)?;

            if !cursor.goto_next_sibling() {
                break;
            }
        }

        let moved = cursor.goto_parent();
        // The parent of the first child must exist, and must be `node`.
        debug_assert!(moved);
        debug_assert!(cursor.node() == node);
    }

    if visible {
        fmt.write_char(')')?;
    }

    Ok(())
}

fn node_is_visible(node: &Node) -> bool {
    node.is_missing() || (node.is_named() && node.language().node_kind_is_visible(node.kind_id()))
}