feat: word diffs

src/lib.rs

@@ -145,7 +145,10 @@
 use std::ops::Range;
 use std::slice;
 
-use crate::util::{strip_common_postfix, strip_common_prefix};
+use crate::{
+    sources::words,
+    util::{strip_common_postfix, strip_common_prefix},
+};
 
 pub use crate::slider_heuristic::{
     IndentHeuristic, IndentLevel, NoSliderHeuristic, SliderHeuristic,
@@ -416,6 +419,45 @@ impl Hunk {
     pub fn is_pure_removal(&self) -> bool {
         self.after.is_empty()
     }
+
+    /// Performs a word-diff of the hunk
+    pub fn word_diff<'a>(
+        &self,
+        input: &InternedInput<&'a str>,
+        diff_input: &mut InternedInput<&'a str>,
+        diff: &mut Diff,
+    ) {
+        let Hunk { before, after } = self.clone();
+        diff_input.update_before(
+            before
+                .map(|index| input.before[index as usize])
+                .map(|token| input.interner[token])
+                .flat_map(|line| words(line)),
+        );
+        diff_input.update_after(
+            after
+                .map(|index| input.after[index as usize])
+                .map(|token| input.interner[token])
+                .flat_map(|line| words(line)),
+        );
+        diff.removed.clear();
+        diff.removed.resize(diff_input.before.len(), false);
+        diff.added.clear();
+        diff.added.resize(diff_input.after.len(), false);
+        if self.is_pure_removal() {
+            diff.removed.fill(true);
+        } else if self.is_pure_insertion() {
+            diff.added.fill(true);
+        } else {
+            diff.compute_with(
+                Algorithm::Myers,
+                &diff_input.before,
+                &diff_input.after,
+                diff_input.interner.num_tokens(),
+            );
+            diff.postprocess_no_heuristic(diff_input);
+        }
+    }
 }
 
 /// Yields all [`Hunk`]s in a file in monotonically increasing order.

src/sources.rs

@@ -17,6 +17,14 @@ pub fn lines(data: &str) -> Lines<'_> {
     Lines(ByteLines(data.as_bytes()))
 }
 
+/// Returns a [`TokenSource`] that uses the words in `data` as Tokens. A word is
+/// a sequence of alphanumeric characters as determined by
+/// `char::is_alphanumeric`, or a sequence of just the space character ' '. Any
+/// other characters are their own word.
+pub fn words(data: &str) -> Words<'_> {
+    Words(data)
+}
+
 /// Returns a [`TokenSource`] that uses the lines in `data` as Tokens. The newline
 /// separator (`\r\n` or `\n`) is included in the emitted tokens. This means that changing
 /// the newline separator from `\r\n` to `\n` (or omitting it fully on the last line) is
@@ -84,6 +92,53 @@ impl<'a> TokenSource for Lines<'a> {
     }
 }
 
+/// A [`TokenSource`] that returns the words of a string as tokens. See
+/// [`words`] for details.
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct Words<'a>(&'a str);
+
+impl<'a> Iterator for Words<'a> {
+    type Item = &'a str;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.0.is_empty() {
+            return None;
+        }
+
+        let initial = self.0.chars().next().unwrap();
+        let word_len = if initial == ' ' {
+            self.0
+                .char_indices()
+                .find(|(_, c)| *c != ' ')
+                .map_or(self.0.len(), |(index, _)| index)
+        } else if initial.is_alphanumeric() {
+            self.0
+                .char_indices()
+                .find(|(_, c)| !c.is_alphanumeric() && *c != '_')
+                .map_or(self.0.len(), |(index, _)| index)
+        } else {
+            initial.len_utf8()
+        };
+
+        let (word, rem) = self.0.split_at(word_len);
+        self.0 = rem;
+        Some(word)
+    }
+}
+impl<'a> TokenSource for Words<'a> {
+    type Token = &'a str;
+
+    type Tokenizer = Self;
+
+    fn tokenize(&self) -> Self::Tokenizer {
+        *self
+    }
+
+    fn estimate_tokens(&self) -> u32 {
+        (self.0.len() / 3) as u32
+    }
+}
+
 /// A [`TokenSource`] that returns the lines of a byte slice as tokens. See [`byte_lines`]
 /// for details.
 #[derive(Clone, Copy, PartialEq, Eq)]

src/tests.rs

@@ -7,9 +7,20 @@ use expect_test::{expect, expect_file};
 // use git_repository as git;
 
 use crate::intern::InternedInput;
+use crate::sources::words;
 use crate::unified_diff::BasicLineDiffPrinter;
 use crate::{Algorithm, Diff, UnifiedDiffConfig};
 
+#[test]
+fn words_tokenizer() {
+    let text = "Hello,  imara!\n (foo-bar_baz)";
+    let tokens = words(text).collect::<Vec<_>>();
+    assert_eq!(
+        tokens,
+        vec!["Hello", ",", "  ", "imara", "!", "\n", " ", "(", "foo", "-", "bar_baz", ")"]
+    );
+}
+
 #[test]
 fn postprocess() {
     let before = r#"
@@ -320,6 +331,135 @@ i
     }
 }
 
+#[test]
+fn hunk_word_diff_pure() {
+    let before = r#"fn foo() -> Bar{
+    let mut foo = 2.0;
+    foo *= 100 / 2;
+}"#;
+    let after = r#"fn foo() -> Bar{
+    let mut foo = 2.0;
+    foo *= 100 / 2;
+    println("hello world")
+}"#;
+    let mut input = InternedInput::new(before, after);
+    for algorithm in Algorithm::ALL {
+        let mut diff_input = InternedInput::default();
+        let mut d = Diff::default();
+
+        println!("{algorithm:?}");
+
+        let mut diff = Diff::compute(algorithm, &input);
+        diff.postprocess_lines(&input);
+
+        let mut hunks = diff.hunks();
+        let hunk = hunks.next().expect("missing first hunk");
+        hunk.word_diff(&input, &mut diff_input, &mut d);
+        let mut h = d.hunks();
+        let first = h.next().expect("missing first inner hunk");
+        assert!(first.is_pure_insertion());
+        assert_eq!(first.before, 0..0);
+        assert_eq!(
+            first.after,
+            0..words("    println(\"hello world\")\n").count() as u32
+        );
+        assert_eq!(h.next(), None);
+        assert_eq!(hunks.next(), None);
+
+        swap(&mut input.before, &mut input.after);
+
+        let mut diff = Diff::compute(algorithm, &input);
+        diff.postprocess_lines(&input);
+
+        let mut hunks = diff.hunks();
+        let hunk = hunks.next().expect("missing first hunk");
+        hunk.word_diff(&input, &mut diff_input, &mut d);
+        let mut h = d.hunks();
+        let first = h.next().expect("missing first inner hunk");
+        assert!(first.is_pure_removal());
+        assert_eq!(
+            first.before,
+            0..words("    println(\"hello world\")\n").count() as u32
+        );
+        assert_eq!(first.after, 0..0);
+        assert_eq!(h.next(), None);
+        assert_eq!(hunks.next(), None);
+
+        swap(&mut input.before, &mut input.after);
+    }
+}
+
+#[test]
+fn hunk_word_diff_modify() {
+    let before = r#"fn foo() -> Bar {
+    let mut foo = 2.0;
+    foo *= 100 / 2;
+}"#;
+    let after = r#"fn foo() -> Bar {
+    let mut foo = 3.0 * 2.0;
+    foo += 100 / 2;
+}"#;
+    let mut input = InternedInput::new(before, after);
+    for algorithm in Algorithm::ALL {
+        let mut diff_input = InternedInput::default();
+        let mut d = Diff::default();
+
+        println!("{algorithm:?}");
+
+        let mut diff = Diff::compute(algorithm, &input);
+        diff.postprocess_lines(&input);
+
+        let mut hunks = diff.hunks();
+        let hunk = hunks.next().expect("missing first hunk");
+        hunk.word_diff(&input, &mut diff_input, &mut d);
+        let mut h = d.hunks();
+        let first = h.next().expect("missing first inner hunk");
+        assert!(first.is_pure_insertion());
+        let off = words("    let mut foo = ").count() as u32;
+        assert_eq!(first.before, off..off);
+        let ins = words("3.0 * ").count() as u32;
+        assert_eq!(first.after, off..ins + off);
+        let second = h.next().expect("missing second inner hunk");
+        let off = words(
+            r#"    let mut foo = 2.0;
+    foo "#,
+        )
+        .count() as u32;
+        assert_eq!(second.before, off..1 + off);
+        assert_eq!(second.after, ins + off..1 + ins + off);
+        assert_eq!(h.next(), None);
+        assert_eq!(hunks.next(), None);
+
+        swap(&mut input.before, &mut input.after);
+
+        let mut diff = Diff::compute(algorithm, &input);
+        diff.postprocess_lines(&input);
+
+        let mut hunks = diff.hunks();
+        let hunk = hunks.next().expect("missing first hunk");
+        hunk.word_diff(&input, &mut diff_input, &mut d);
+        let mut h = d.hunks();
+        let first = h.next().expect("missing first inner hunk");
+        assert!(first.is_pure_removal());
+        let off = words("    let mut foo = ").count() as u32;
+        let rem = words("3.0 * ").count() as u32;
+        assert_eq!(first.before, off..rem + off);
+        assert_eq!(first.after, off..off);
+        let second = h.next().expect("missing second inner hunk");
+        let off = words(
+            r#"    let mut foo = 2.0;
+    foo "#,
+        )
+        .count() as u32;
+        assert_eq!(second.before, rem + off..1 + rem + off);
+        assert_eq!(second.after, off..1 + off);
+        assert_eq!(h.next(), None);
+        assert_eq!(hunks.next(), None);
+
+        swap(&mut input.before, &mut input.after);
+    }
+}
+
 pub fn project_root() -> PathBuf {
     let dir = env!("CARGO_MANIFEST_DIR");
     let mut res = PathBuf::from(dir);