.

tests/idempotence.rs

@@ -1,4 +1,6 @@
-use reconcile_text::{BuiltinTokenizer, Token, reconcile};
+use reconcile_text::{
+    BuiltinTokenizer, CursorPosition, EditedText, TextWithCursors, Token, reconcile,
+};
 use test_case::{test_case, test_matrix};
 
 #[test_matrix([
@@ -79,3 +81,265 @@ fn identical_edits_preserve_original_spelling(parent: &str, updated: &str) {
         updated,
     );
 }
+
+#[test_matrix([
+    BuiltinTokenizer::Character,
+    BuiltinTokenizer::Line,
+    BuiltinTokenizer::Markdown,
+    BuiltinTokenizer::Word
+])]
+fn replay_short_edits_preserves_merged_text(tokenizer: BuiltinTokenizer) {
+    let mut texts = vec![String::new()];
+    let mut level = texts.clone();
+    for _ in 0..2 {
+        level = level
+            .iter()
+            .flat_map(|text| ['a', 'b', ' ', '\n'].map(|ch| format!("{text}{ch}")))
+            .collect();
+        texts.extend(level.iter().cloned());
+    }
+
+    for parent in &texts {
+        for left in &texts {
+            for right in &texts {
+                let merged = reconcile(parent, &left.into(), &right.into(), &*tokenizer).apply();
+                assert_eq!(
+                    reconcile(parent, &right.into(), &left.into(), &*tokenizer)
+                        .apply()
+                        .text(),
+                    merged.text(),
+                    "swapped inputs: tokenizer={tokenizer:?}, parent={parent:?}, left={left:?}, right={right:?}",
+                );
+                for replayed in [left, right] {
+                    let actual = reconcile(parent, &merged, &replayed.into(), &*tokenizer).apply();
+                    assert_eq!(
+                        actual.text(),
+                        merged.text(),
+                        "tokenizer={tokenizer:?}, parent={parent:?}, left={left:?}, right={right:?}, replayed={replayed:?}"
+                    );
+                }
+            }
+        }
+    }
+}
+
+#[test_matrix(["", "a"], [
+    BuiltinTokenizer::Character,
+    BuiltinTokenizer::Line,
+    BuiltinTokenizer::Markdown,
+    BuiltinTokenizer::Word
+])]
+fn replay_conflicting_replacements_keeps_both_edits(parent: &str, tokenizer: BuiltinTokenizer) {
+    let left = TextWithCursors::new("b".to_owned(), vec![CursorPosition::new(1, 1)]);
+    let right = TextWithCursors::new("x".to_owned(), vec![CursorPosition::new(2, 1)]);
+    let merged = reconcile(parent, &left, &right, &*tokenizer).apply();
+    assert_eq!(merged.text(), "bx");
+    assert_eq!(
+        merged.cursors(),
+        vec![CursorPosition::new(1, 1), CursorPosition::new(2, 2)]
+    );
+    for input in ["b", "x"] {
+        let replayed = reconcile(parent, &merged, &input.into(), &*tokenizer).apply();
+        assert_eq!(replayed, merged);
+    }
+    let left_operations = EditedText::from_strings_with_tokenizer(parent, &left, &*tokenizer);
+    let right_operations = EditedText::from_strings_with_tokenizer(parent, &right, &*tokenizer);
+    assert_eq!(
+        left_operations
+            .merge_with_tokenizer(&right_operations, &*tokenizer)
+            .apply(),
+        merged
+    );
+}
+
+#[test_matrix([
+    BuiltinTokenizer::Character,
+    BuiltinTokenizer::Line,
+    BuiltinTokenizer::Markdown,
+    BuiltinTokenizer::Word
+])]
+fn replay_preserves_repeated_text_and_unicode_cursors(tokenizer: BuiltinTokenizer) {
+    let merged = reconcile("a", &"bb".into(), &"x".into(), &*tokenizer).apply();
+    assert_eq!(merged.text(), "bbx");
+    assert_eq!(
+        reconcile("a", &merged, &"x".into(), &*tokenizer).apply(),
+        merged
+    );
+
+    let left = TextWithCursors::new(
+        "🦊x".to_owned(),
+        vec![CursorPosition::new(1, 1), CursorPosition::new(2, 2)],
+    );
+    let right = TextWithCursors::new("x".to_owned(), vec![CursorPosition::new(3, 1)]);
+    let edited = reconcile("a", &left, &right, &*tokenizer);
+    let result = edited.apply();
+    assert_eq!(result.text(), "🦊x");
+    for (id, position) in [(1, 1), (2, 2), (3, 2)] {
+        assert!(
+            result
+                .cursors()
+                .contains(&CursorPosition::new(id, position))
+        );
+    }
+    let history_text: String = edited
+        .apply_with_history()
+        .iter()
+        .filter(|span| {
+            !matches!(
+                span.history(),
+                reconcile_text::History::RemovedFromLeft
+                    | reconcile_text::History::RemovedFromRight
+            )
+        })
+        .map(reconcile_text::SpanWithHistory::text)
+        .collect();
+    assert_eq!(history_text, result.text());
+    assert_eq!(edited.apply_with_all().0, result);
+}
+
+#[test_matrix([
+    BuiltinTokenizer::Character,
+    BuiltinTokenizer::Line,
+    BuiltinTokenizer::Markdown,
+    BuiltinTokenizer::Word
+])]
+fn replay_longer_mixed_edits_is_stable(tokenizer: BuiltinTokenizer) {
+    let mut seed = 0x12ab_34cd_56ef_7890u64;
+    let mut next = || {
+        seed ^= seed << 13;
+        seed ^= seed >> 7;
+        seed ^= seed << 17;
+        seed
+    };
+    let alphabet = ['a', 'b', 'c', ' ', '\n', '\r', 'é', '🦊'];
+    for case in 0..2000 {
+        let mut text = || {
+            (0..next() % 16)
+                .map(|_| alphabet[usize::try_from(next() % 8).unwrap()])
+                .collect::<String>()
+        };
+        let parent = text();
+        let left = text();
+        let right = text();
+        let merged = reconcile(
+            &parent,
+            &left.clone().into(),
+            &right.clone().into(),
+            &*tokenizer,
+        )
+        .apply();
+        if case < 200 {
+            let left_with_cursors = TextWithCursors::new(
+                left.clone(),
+                (0..=left.chars().count())
+                    .map(|position| CursorPosition::new(position, position))
+                    .collect(),
+            );
+            let right_with_cursors = TextWithCursors::new(
+                right.clone(),
+                (0..=right.chars().count())
+                    .map(|position| CursorPosition::new(100 + position, position))
+                    .collect(),
+            );
+            let result = reconcile(
+                &parent,
+                &left_with_cursors,
+                &right_with_cursors,
+                &*tokenizer,
+            )
+            .apply();
+            assert_eq!(result.text(), merged.text());
+            assert_eq!(
+                result.cursors().len(),
+                left_with_cursors.cursors().len() + right_with_cursors.cursors().len()
+            );
+            assert!(
+                result
+                    .cursors()
+                    .iter()
+                    .all(|cursor| cursor.char_index() <= result.text().chars().count())
+            );
+            for cursor in left_with_cursors
+                .cursors()
+                .into_iter()
+                .chain(right_with_cursors.cursors())
+            {
+                assert!(
+                    result
+                        .cursors()
+                        .iter()
+                        .any(|updated| updated.id() == cursor.id())
+                );
+            }
+        }
+        for input in [&left, &right] {
+            assert_eq!(
+                reconcile(&parent, &merged, &input.into(), &*tokenizer)
+                    .apply()
+                    .text(),
+                merged.text(),
+                "tokenizer={tokenizer:?}, parent={parent:?}, left={left:?}, right={right:?}, input={input:?}"
+            );
+        }
+        assert_eq!(
+            reconcile(&parent, &right.into(), &left.into(), &*tokenizer)
+                .apply()
+                .text(),
+            merged.text()
+        );
+    }
+}
+
+#[test]
+fn replay_with_normalized_tokens_preserves_spelling() {
+    let tokenizer = |text: &str| {
+        text.chars()
+            .map(|ch| Token::new(ch.to_ascii_lowercase(), ch.to_string(), false, false))
+            .collect()
+    };
+    let texts = ["", "A", "a", "AB", "ba", "Aa", "a A", " A", "\nA"];
+    for parent in texts {
+        for left in texts {
+            for right in texts {
+                let merged = reconcile(parent, &left.into(), &right.into(), &tokenizer).apply();
+                for input in [left, right] {
+                    assert_eq!(
+                        reconcile(parent, &merged, &input.into(), &tokenizer)
+                            .apply()
+                            .text(),
+                        merged.text()
+                    );
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn ambiguous_ancestral_text_prefers_a_stable_input() {
+    let parent = "a b ";
+    let left = "a b a b ".into();
+    let right = "c d ".into();
+    let tokenizer = &*BuiltinTokenizer::Word;
+    let result = reconcile(parent, &left, &right, tokenizer);
+    let merged = result.apply();
+    assert_eq!(merged.text(), "a b a b ");
+    for input in [&left, &right] {
+        assert_eq!(
+            reconcile(parent, &merged, input, tokenizer).apply().text(),
+            merged.text()
+        );
+    }
+    assert!(
+        result
+            .apply_with_history()
+            .iter()
+            .any(|span| span.history() == reconcile_text::History::AddedFromLeft)
+    );
+    assert!(
+        !result
+            .apply_with_history()
+            .iter()
+            .any(|span| span.history() == reconcile_text::History::AddedFromRight)
+    );
+}