difference/

lib.rs

//! Functions to find the difference between two texts (strings).
//! Usage
//! ----------
//!
//! Add the following to your `Cargo.toml`:
//!
//! ```toml
//! [dependencies]
//! difference = "2.0"
//! ```
//!
//! Now you can use the crate in your code
//! ```ignore
//! extern crate difference;
//! ```
//!
//! ## Examples
//!
//! See [Examples.md](Examples.md) for more examples.
//!
//! ```rust
//! use difference::{Difference, Changeset};
//!
//! let changeset = Changeset::new("test", "tent", "");
//!
//! assert_eq!(changeset.diffs, vec![
//!   Difference::Same("te".to_string()),
//!   Difference::Rem("s".to_string()),
//!   Difference::Add("n".to_string()),
//!   Difference::Same("t".to_string())
//! ]);
//! ```

#![crate_name = "difference"]
#![doc(html_root_url = "http://docs.rs/difference")]
#![deny(missing_docs)]
#![deny(warnings)]

mod lcs;
mod merge;
mod display;

use lcs::lcs;
use merge::merge;

/// Defines the contents of a changeset
/// Changesets will be delivered in order of appearance in the original string
/// Sequences of the same kind will be grouped into one Difference
#[derive(PartialEq, Debug)]
pub enum Difference {
    /// Sequences that are the same
    Same(String),
    /// Sequences that are an addition (don't appear in the first string)
    Add(String),
    /// Sequences that are a removal (don't appear in the second string)
    Rem(String),
}

/// The information about a full changeset
pub struct Changeset {
    /// An ordered vector of `Difference` objects, coresponding
    /// to the differences within the text
    pub diffs: Vec<Difference>,
    /// The split used when creating the `Changeset`
    /// Common splits are `""` for char-level, `" "` for word-level and `"\n"` for line-level.
    pub split: String,
    /// The edit distance of the `Changeset`
    pub distance: i32,
}

impl Changeset {
    /// Calculates the edit distance and the changeset for two given strings.
    /// The first string is assumed to be the "original", the second to be an
    /// edited version of the first. The third parameter specifies how to split
    /// the input strings, leading to a more or less exact comparison.
    ///
    /// Common splits are `""` for char-level, `" "` for word-level and `"\n"` for line-level.
    ///
    /// Outputs the edit distance (how much the two strings differ) and a "changeset", that is
    /// a `Vec` containing `Difference`s.
    ///
    /// # Examples
    ///
    /// ```
    /// use difference::{Changeset, Difference};
    ///
    /// let changeset = Changeset::new("test", "tent", "");
    ///
    /// assert_eq!(changeset.diffs, vec![
    ///     Difference::Same("te".to_string()),
    ///     Difference::Rem("s".to_string()),
    ///     Difference::Add("n".to_string()),
    ///     Difference::Same("t".to_string())
    /// ]);
    /// ```
    pub fn new(orig: &str, edit: &str, split: &str) -> Changeset {
        let (dist, common) = lcs(orig, edit, split);
        Changeset {
            diffs: merge(orig, edit, &common, split),
            split: split.to_string(),
            distance: dist,
        }
    }
}

/// **This function is deprecated, please use `Changeset::new` instead**
///
/// Calculates the edit distance and the changeset for two given strings.
/// The first string is assumed to be the "original", the second to be an
/// edited version of the first. The third parameter specifies how to split
/// the input strings, leading to a more or less exact comparison.
///
/// Common splits are `""` for char-level, `" "` for word-level and `"\n"` for line-level.
///
/// Outputs the edit distance (how much the two strings differ) and a "changeset", that is
/// a `Vec` containing `Difference`s.
///
/// # Examples
///
/// ```
/// use difference::diff;
/// use difference::Difference;
///
/// let (dist, changeset) = diff("test", "tent", "");
///
/// assert_eq!(changeset, vec![
///     Difference::Same("te".to_string()),
///     Difference::Rem("s".to_string()),
///     Difference::Add("n".to_string()),
///     Difference::Same("t".to_string())
/// ]);
/// ```
#[deprecated(since = "1.0.0", note = "please use `Changeset::new` instead")]
pub fn diff(orig: &str, edit: &str, split: &str) -> (i32, Vec<Difference>) {
    let ch = Changeset::new(orig, edit, split);
    (ch.distance, ch.diffs)
}

/// Assert the difference between two strings. Works like diff, but takes
/// a fourth parameter that is the expected edit distance (e.g. 0 if you want to
/// test for equality).
///
/// To include this macro use:
///
/// ```
/// #[macro_use(assert_diff)]
/// extern crate difference;
/// # fn main() { }
/// ```
///
/// Remember that edit distance might not be equal to your understanding of difference,
/// for example the words "Rust" and "Dust" have an edit distance of 2 because two changes (a
/// removal and an addition) are required to make them look the same.
///
/// Will print an error with a colorful diff in case of failure.
#[macro_export]
macro_rules! assert_diff {
    ($orig:expr , $edit:expr, $split: expr, $expected: expr) => ({
        let orig = $orig;
        let edit = $edit;

        let changeset = $crate::Changeset::new(orig, edit, &($split));
        if changeset.distance != $expected {
            println!("{}", changeset);
            panic!("assertion failed: edit distance between {:?} and {:?} is {} and not {}, see \
                    diffset above",
                   orig,
                   edit,
                   changeset.distance,
                   &($expected))
        }
    })
}

/// **This function is deprecated, `Changeset` now implements the `Display` trait instead**
///
/// Prints a colorful visual representation of the diff.
/// This is just a convenience function for those who want quick results.
///
/// I recommend checking out the examples on how to build your
/// own diff output.
/// # Examples
///
/// ```
/// use difference::print_diff;
/// print_diff("Diffs are awesome", "Diffs are cool", " ");
/// ```
#[deprecated(since = "1.0.0", note = "`Changeset` now implements the `Display` trait instead")]
pub fn print_diff(orig: &str, edit: &str, split: &str) {
    let ch = Changeset::new(orig, edit, split);
    println!("{}", ch);
}

#[test]
fn test_diff() {
    let text1 = "Roses are red, violets are blue,\n\
                 I wrote this library,\n\
                 just for you.\n\
                 (It's true).";

    let text2 = "Roses are red, violets are blue,\n\
                 I wrote this documentation,\n\
                 just for you.\n\
                 (It's quite true).";

    let changeset = Changeset::new(text1, text2, "\n");

    assert_eq!(changeset.distance, 4);

    assert_eq!(
        changeset.diffs,
        vec![
            Difference::Same("Roses are red, violets are blue,".to_string()),
            Difference::Rem("I wrote this library,".to_string()),
            Difference::Add("I wrote this documentation,".to_string()),
            Difference::Same("just for you.".to_string()),
            Difference::Rem("(It's true).".to_string()),
            Difference::Add("(It's quite true).".to_string()),
        ]
    );
}

#[test]
fn test_diff_brief() {
    let text1 = "Hello\nworld";
    let text2 = "Ola\nmundo";

    let changeset = Changeset::new(text1, text2, "\n");

    assert_eq!(
        changeset.diffs,
        vec![
            Difference::Rem("Hello\nworld".to_string()),
            Difference::Add("Ola\nmundo".to_string()),
        ]
    );
}

#[test]
fn test_diff_smaller_line_count_on_left() {
    let text1 = "Hello\nworld";
    let text2 = "Ola\nworld\nHow is it\ngoing?";

    let changeset = Changeset::new(text1, text2, "\n");

    assert_eq!(
        changeset.diffs,
        vec![
            Difference::Rem("Hello".to_string()),
            Difference::Add("Ola".to_string()),
            Difference::Same("world".to_string()),
            Difference::Add("How is it\ngoing?".to_string()),
        ]
    );
}

#[test]
fn test_diff_smaller_line_count_on_right() {
    let text1 = "Hello\nworld\nWhat a \nbeautiful\nday!";
    let text2 = "Ola\nworld";

    let changeset = Changeset::new(text1, text2, "\n");

    assert_eq!(
        changeset.diffs,
        vec![
            Difference::Rem("Hello".to_string()),
            Difference::Add("Ola".to_string()),
            Difference::Same("world".to_string()),
            Difference::Rem("What a \nbeautiful\nday!".to_string()),
        ]
    );
}

#[test]
fn test_diff_similar_text_with_smaller_line_count_on_right() {
    let text1 = "Hello\nworld\nWhat a \nbeautiful\nday!";
    let text2 = "Hello\nwoRLd";

    let changeset = Changeset::new(text1, text2, "\n");

    assert_eq!(
        changeset.diffs,
        vec![
            Difference::Same("Hello".to_string()),
            Difference::Rem("world\nWhat a \nbeautiful\nday!".to_string()),
            Difference::Add("woRLd".to_string()),
        ]
    );
}

#[test]
fn test_diff_similar_text_with_similar_line_count() {
    let text1 = "Hello\nworld\nWhat a \nbeautiful\nday!";
    let text2 = "Hello\nwoRLd\nbeautiful";

    let changeset = Changeset::new(text1, text2, "\n");

    assert_eq!(
        changeset.diffs,
        vec![
            Difference::Same("Hello".to_string()),
            Difference::Rem("world\nWhat a ".to_string()),
            Difference::Add("woRLd".to_string()),
            Difference::Same("beautiful".to_string()),
            Difference::Rem("day!".to_string()),
        ]
    );
}

#[test]
#[should_panic]
fn test_assert_diff_panic() {
    let text1 = "Roses are red, violets are blue,\n\
                 I wrote this library,\n\
                 just for you.\n\
                 (It's true).";

    let text2 = "Roses are red, violets are blue,\n\
                 I wrote this documentation,\n\
                 just for you.\n\
                 (It's quite true).";

    assert_diff!(text1, text2, "\n'", 0);
}

#[test]
fn test_assert_diff() {
    let text1 = "Roses are red, violets are blue";

    let text2 = "Roses are green, violets are blue";

    assert_diff!(text1, text2, " ", 2);
}