exn 0.3.1

A context-aware concrete Error type built on `core::error::Error`.
Documentation 
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// Copyright 2025 FastLabs Developers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use alloc::format;
use core::error::Error;
use core::fmt;

use crate::Exn;
use crate::Frame;

impl<E: Error + Send + Sync + 'static> fmt::Debug for Exn<E> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write_exn(f, self.frame(), 0, "")
    }
}

impl fmt::Debug for Frame {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write_exn(f, self, 0, "")
    }
}

fn write_exn(f: &mut fmt::Formatter<'_>, frame: &Frame, level: usize, prefix: &str) -> fmt::Result {
    write!(f, "{}", frame.error())?;

    let location = frame.location();
    write!(
        f,
        ", at {}:{}:{}",
        location.file(),
        location.line(),
        location.column()
    )?;

    let children = frame.children();
    let children_len = children.len();

    for (i, child) in children.iter().enumerate() {
        let child_child_len = child.children().len();
        let is_linear = level == 0 && children_len == 1 && child_child_len == 1;

        if i != children_len - 1 || is_linear {
            write!(f, "\n{}|-- ", prefix)?;
        } else {
            write!(f, "\n{}`-- ", prefix)?;
        }

        if is_linear {
            write_exn(f, child, 0, prefix)?;
        } else if i < children_len - 1 {
            write_exn(f, child, level + 1, &format!("{}|   ", prefix))?;
        } else {
            write_exn(f, child, level + 1, &format!("{}    ", prefix))?;
        }
    }

    Ok(())
}