specker 0.3.5

Testing utility that simplifies file matching against bunch of templates.
Documentation 
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// Copyright 2017 Nerijus Arlauskas
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.

use std::fmt;
use std::fs;
use std::io::BufRead;
use std::io::BufReader;
use std::io::Read;
use std::path::Path;
use {At, Error};

/// Display nice error that combines line and column info with file contents.
pub fn display_error<E: DisplayError>(e: &E) -> String {
    e.display_error()
}

/// Display nice error that combines line and column info with file contents
/// but error itself does not have file path info.
pub fn display_error_for_file<E: DisplayErrorForFile>(path: &Path, e: &E) -> String {
    e.display_error_for_file(path)
}

/// Display nice error that combines line and column info with file source contents.
pub fn display_error_for_read<E: DisplayErrorForRead, I: Read>(
    path: &Path,
    input: &mut I,
    e: &E,
) -> String {
    e.display_error_for_read(path, input)
}

pub trait DisplayError {
    fn display_error(&self) -> String;
}

impl DisplayError for Error {
    fn display_error(&self) -> String {
        match *self {
            Error::Parse { ref path, ref err } => err.display_error_for_file(path),
            ref other => format!("{}", other),
        }
    }
}

pub trait DisplayErrorForRead {
    fn display_error_for_read<I: Read>(&self, display_file_name: &Path, path: &mut I) -> String;
}

pub trait DisplayErrorForFile {
    fn display_error_for_file(&self, path: &Path) -> String;
}

impl<T> DisplayErrorForFile for At<T>
where
    T: fmt::Display + fmt::Debug,
{
    fn display_error_for_file(&self, path: &Path) -> String {
        let mut file = fs::File::open(path).expect("failed to open file");

        if self.lo.line == self.hi.line {
            // does not handle errors that span multiple lines
            return self.display_error_for_read(path, &mut file);
        }

        unimplemented!("multi line errors are not implemented");
    }
}

impl<T> DisplayErrorForRead for At<T>
where
    T: fmt::Display + fmt::Debug,
{
    fn display_error_for_read<I: Read>(&self, display_file_name: &Path, file: &mut I) -> String {
        let mut extra_message = None;

        let mut lines: Option<Vec<String>> = None;

        for (i, rd_line) in BufReader::new(file).lines().enumerate() {
            if let Ok(rd_line) = rd_line {
                if i + 3 > self.lo.line && i <= self.lo.line {
                    let line = if rd_line.len() > 80 {
                        format!("{}..", &rd_line[..78])
                    } else {
                        rd_line.to_string()
                    };
                    if let Some(ref mut lines) = lines {
                        lines.push(line);
                    } else {
                        lines = Some(vec![line])
                    }
                }
            }
        }
        if let None = lines {
            lines = Some(vec![String::from("")]);
        }

        if let Some(lines) = lines {
            let mut sb = String::new();

            // print lines

            let lines_len = lines.len();
            let mut num_len = 0;
            for (i, line) in lines.into_iter().enumerate() {
                let num = format!("{} ", self.lo.line + i + 2 - lines_len);
                num_len = num.len();

                sb.push_str(&num);
                sb.push_str("| ");
                sb.push_str(&line);
                sb.push_str("\n");
            }

            // print arrow

            for _ in 0..num_len {
                sb.push_str(" ");
            }
            sb.push_str("| ");

            for _ in 0..self.lo.col {
                sb.push_str(" ");
            }
            sb.push_str("^");
            for _ in self.lo.col + 1..self.hi.col {
                sb.push_str("^");
            }

            sb.push_str("\n");

            // print message

            for _ in 0..num_len {
                sb.push_str(" ");
            }
            sb.push_str("| ");

            for _ in 0..self.lo.col {
                sb.push_str(" ");
            }
            sb.push_str(&format!("{}", self.desc));

            extra_message = Some(sb);
        }

        if let Some(extra_message) = extra_message {
            format!("in {:?}\n{}", display_file_name, extra_message)
        } else {
            if self.lo == self.hi {
                format!("{} in {:?} at {}", &self.desc, display_file_name, self.lo)
            } else {
                format!(
                    "{} in {:?} at {} - {}",
                    &self.desc, display_file_name, self.lo, self.hi
                )
            }
        }
    }
}