core: Improve changeset composition behavior.
It would fail to combine with an empty set.
This commit is contained in:
Blaž Hrastnik
parent
cf7b19d711
commit
f00cb15137
1 changed files with 69 additions and 32 deletions
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@ -27,15 +27,35 @@ pub struct ChangeSet {
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pub(crate) changes: Vec<Operation>,
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/// The required document length. Will refuse to apply changes unless it matches.
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len: usize,
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len_after: usize,
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}
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impl Default for ChangeSet {
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fn default() -> Self {
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Self {
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changes: Vec::new(),
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len: 0,
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len_after: 0,
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}
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}
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}
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impl ChangeSet {
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pub fn with_capacity(capacity: usize) -> Self {
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Self {
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changes: Vec::with_capacity(capacity),
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len: 0,
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len_after: 0,
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}
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}
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#[must_use]
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pub fn new(doc: &Rope) -> Self {
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let len = doc.len_chars();
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Self {
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changes: vec![Operation::Retain(len)],
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changes: Vec::new(),
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len,
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len_after: len,
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}
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}
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@ -47,21 +67,6 @@ impl ChangeSet {
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&self.changes
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}
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#[must_use]
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fn len_after(&self) -> usize {
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use Operation::*;
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let mut len = 0;
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for change in &self.changes {
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match change {
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Retain(i) => len += i,
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Insert(s) => len += s.chars().count(),
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Delete(_) => (),
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}
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}
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len
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}
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// Changeset builder operations: delete/insert/retain
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fn delete(&mut self, n: usize) {
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use Operation::*;
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@ -69,6 +74,8 @@ impl ChangeSet {
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return;
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}
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self.len += n;
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if let Some(Delete(count)) = self.changes.last_mut() {
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*count += n;
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} else {
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@ -83,6 +90,8 @@ impl ChangeSet {
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return;
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}
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self.len_after += fragment.len();
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let new_last = match self.changes.as_mut_slice() {
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[.., Insert(prev)] | [.., Insert(prev), Delete(_)] => {
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prev.push_tendril(&fragment);
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@ -101,6 +110,9 @@ impl ChangeSet {
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return;
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}
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self.len += n;
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self.len_after += n;
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if let Some(Retain(count)) = self.changes.last_mut() {
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*count += n;
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} else {
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@ -112,7 +124,13 @@ impl ChangeSet {
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/// In other words, If `this` goes `docA` → `docB` and `other` represents `docB` → `docC`, the
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/// returned value will represent the change `docA` → `docC`.
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pub fn compose(self, other: Self) -> Self {
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debug_assert!(self.len_after() == other.len);
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debug_assert!(self.len_after == other.len);
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// composing fails in weird ways if one of the sets is empty
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// a: [] len: 0 len_after: 1 | b: [Insert(Tendril<UTF8>(inline: "\n")), Retain(1)] len 1
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if self.changes.is_empty() {
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return other;
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}
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let len = self.changes.len();
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@ -122,10 +140,7 @@ impl ChangeSet {
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let mut head_a = changes_a.next();
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let mut head_b = changes_b.next();
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let mut changes = Self {
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len: self.len,
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changes: Vec::with_capacity(len), // TODO: max(a, b), shrink_to_fit() afterwards
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};
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let mut changes = Self::with_capacity(len); // TODO: max(a, b), shrink_to_fit() afterwards
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loop {
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use std::cmp::Ordering;
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@ -228,6 +243,9 @@ impl ChangeSet {
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};
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}
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// starting len should still equal original starting len
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debug_assert!(changes.len == self.len);
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changes
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}
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@ -251,7 +269,8 @@ impl ChangeSet {
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pub fn invert(&self, original_doc: &Rope) -> Self {
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assert!(original_doc.len_chars() == self.len);
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let mut changes = Vec::with_capacity(self.changes.len());
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let mut changes = Self::with_capacity(self.changes.len());
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let mut pos = 0;
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let mut len = 0;
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@ -259,24 +278,22 @@ impl ChangeSet {
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use Operation::*;
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match change {
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Retain(n) => {
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changes.push(Retain(*n));
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changes.retain(*n);
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pos += n;
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len += n;
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}
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Delete(n) => {
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let text = Cow::from(original_doc.slice(pos..pos + *n));
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changes.push(Insert(Tendril::from_slice(&text)));
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changes.insert(Tendril::from_slice(&text));
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pos += n;
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}
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Insert(s) => {
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let chars = s.chars().count();
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changes.push(Delete(chars));
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len += chars;
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changes.delete(chars);
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}
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}
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}
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Self { changes, len }
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changes
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}
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/// Returns true if applied successfully.
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@ -309,7 +326,7 @@ impl ChangeSet {
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/// `true` when the set is empty.
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#[inline]
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pub fn is_empty(&self) -> bool {
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matches!(self.changes.as_slice(), [] | [Operation::Retain(_)])
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self.changes.is_empty()
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}
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/// Map a position through the changes.
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@ -458,8 +475,8 @@ impl Transaction {
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I: IntoIterator<Item = Change> + ExactSizeIterator,
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{
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let len = doc.len_chars();
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let acc = Vec::with_capacity(2 * changes.len() + 1); // rough estimate
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let mut changeset = ChangeSet { changes: acc, len };
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let mut changeset = ChangeSet::with_capacity(2 * changes.len() + 1); // rough estimate
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// TODO: verify ranges are ordered and not overlapping or change will panic.
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@ -576,11 +593,13 @@ mod test {
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Insert("abc".into()),
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],
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len: 8,
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len_after: 15,
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};
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let b = ChangeSet {
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changes: vec![Delete(10), Insert("world".into()), Retain(5)],
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len: 15,
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len_after: 10,
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};
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let mut text = Rope::from("hello xz");
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@ -597,8 +616,9 @@ mod test {
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use Operation::*;
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let changes = ChangeSet {
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changes: vec![Retain(4), Delete(5), Insert("test".into()), Retain(3)],
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changes: vec![Retain(4), Insert("test".into()), Delete(5), Retain(3)],
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len: 12,
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len_after: 11,
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};
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let doc = Rope::from("世界3 hello xz");
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@ -627,6 +647,7 @@ mod test {
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let cs = ChangeSet {
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changes: vec![Retain(4), Insert("!!".into()), Retain(4)],
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len: 8,
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len_after: 10,
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};
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assert_eq!(cs.map_pos(0, Assoc::Before), 0); // before insert region
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@ -638,6 +659,7 @@ mod test {
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let cs = ChangeSet {
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changes: vec![Retain(4), Delete(4), Retain(4)],
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len: 12,
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len_after: 8,
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};
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assert_eq!(cs.map_pos(0, Assoc::Before), 0); // at start
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assert_eq!(cs.map_pos(4, Assoc::Before), 4); // before a delete
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@ -655,6 +677,7 @@ mod test {
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Delete(2),
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],
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len: 4,
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len_after: 4,
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};
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assert_eq!(cs.map_pos(2, Assoc::Before), 2);
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assert_eq!(cs.map_pos(2, Assoc::After), 2);
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@ -717,4 +740,18 @@ mod test {
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assert_eq!(changes.changes, &[Insert("hello".into())]);
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// instead of insert h, insert e, insert l, insert l, insert o
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}
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#[test]
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fn combine_with_empty() {
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let empty = Rope::from("");
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let mut a = ChangeSet::new(&empty);
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let mut b = ChangeSet::new(&empty);
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b.insert("a".into());
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let changes = a.compose(b);
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use Operation::*;
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assert_eq!(changes.changes, &[Insert("a".into())]);
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}
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}
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