documents: a TOC press follows the edit since its read; filtered tags keep shortcodes; tag names end as HTML5 ends them; block starts end p, li, dd and dt; owed space shifts only what opened after it

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/documents/document/edit.rs

@@ -12,8 +12,27 @@ use crate::{
     forms::{InputEvent, TextInput},
 };
 
+/// The one edit from `old` to `new`, by shared ends.
+pub(super) fn between(old: &str, new: &str) -> Option<(Range<usize>, usize)> {
+    let head: usize = old
+        .chars()
+        .zip(new.chars())
+        .take_while(|(a, b)| a == b)
+        .map(|(ch, _)| ch.len_utf8())
+        .sum();
+    let room = old.len().min(new.len()) - head;
+    let mut tail = 0;
+    for (a, b) in old.chars().rev().zip(new.chars().rev()) {
+        if a != b || tail + a.len_utf8() > room {
+            break;
+        }
+        tail += a.len_utf8();
+    }
+    (old != new).then(|| (head..old.len() - tail, new.len() - tail - head))
+}
+
 /// Where byte `at` lies after `edit`, if it survives.
-fn moved(at: usize, edit: &Option<(Range<usize>, usize)>) -> Option<usize> {
+pub(super) fn moved(at: usize, edit: &Option<(Range<usize>, usize)>) -> Option<usize> {
     match edit {
         None => Some(at),
         Some((replaced, _)) if at < replaced.start => Some(at),
@@ -181,4 +200,15 @@ mod tests {
         assert_eq!(super::moved(3, &edit), None, "inside is gone");
         assert_eq!(super::moved(7, &None), Some(7));
     }
+
+    #[test]
+    fn two_texts_part_at_their_shared_ends() {
+        assert_eq!(super::between("abc", "abc"), None);
+        assert_eq!(super::between("before\nB", "## B\nB"), Some((0..6, 4)));
+        assert_eq!(super::between("ab", "aXb"), Some((1..1, 1)));
+        assert_eq!(super::between("aa", "aaa"), Some((2..2, 1)));
+        assert_eq!(super::between("aXYb", "ab"), Some((1..3, 0)));
+        assert_eq!(super::between("é😄", "é"), Some((2..6, 0)));
+        assert_eq!(super::between("x😄", "y😄"), Some((0..1, 1)));
+    }
 }

src/documents/document/place.rs

@@ -1,6 +1,11 @@
+use std::sync::Arc;
+
 use gpui::{App, Context, Focusable as _, ListOffset, ScrollStrategy, Window, px};
 
-use super::{DocumentHeading, MarkdownDocument, Placement};
+use super::{
+    MarkdownDocument, Placement,
+    edit::{between, moved},
+};
 use crate::documents::{MarkdownMode, modes::joint};
 
 /// Line and column, from zero, of byte `at` in `text`.
@@ -189,27 +194,25 @@ impl MarkdownDocument {
             .saturating_sub(1)
     }
 
-    /// Reveals the pressed heading, found again in the text.
+    /// Reveals the pressed heading, moved by the edit since.
     pub(super) fn reveal_at(&mut self, at: usize, window: &mut Window, cx: &mut Context<Self>) {
-        let headings = &self.parsed.headings;
-        let Some(ix) = headings.iter().position(|heading| heading.at == at) else {
+        if !self.parsed.headings.iter().any(|heading| heading.at == at) {
             return log::warn!("markdown document: a heading read away");
-        };
-        let pressed = headings[ix].clone();
-        let same = |heading: &&DocumentHeading| {
-            (heading.depth, &heading.title) == (pressed.depth, &pressed.title)
-        };
-        let nth = headings[..ix].iter().filter(same).count();
+        }
+        // The heading list drew from this read.
+        let drawn = Arc::clone(&self.parsed);
         if self.commit(cx).is_some() || !self.read_now(cx) {
             self.reparse(true, cx);
         }
         if !self.read_now(cx) {
             return log::warn!("markdown document: a heading pressed while the text is read again");
         }
-        let Some(found) = self.parsed.headings.iter().filter(same).nth(nth) else {
+        let edit = between(&drawn.text, self.editor.read(cx).text());
+        let headings = &self.parsed.headings;
+        let Some(found) = moved(at, &edit).filter(|at| headings.iter().any(|h| h.at == *at)) else {
             return log::warn!("markdown document: the pressed heading changed as one wrote");
         };
-        let line = self.editor.read(cx).buffer.line_of(found.at);
+        let line = self.editor.read(cx).buffer.line_of(found);
         self.reveal(line, window, cx);
     }
 

src/documents/document/tests/toc.rs

@@ -1,6 +1,6 @@
-use gpui::{Modifiers, MouseButton, TestAppContext, VisualTestContext, point, px};
+use gpui::{Entity, Modifiers, MouseButton, TestAppContext, VisualTestContext, point, px};
 
-use super::{MarkdownMode, frames, open, type_in};
+use super::{MarkdownDocument, MarkdownMode, frames, open, type_in};
 
 const LISTED: &str = "[toc]\n\n# A\n\ntext\n\n## B\n";
 
@@ -11,10 +11,76 @@ fn press_entry(ix: usize, modifiers: Modifiers, cx: &mut VisualTestContext) {
         .expect("the entry is drawn");
     let at = point(bounds.left() + px(2.0), bounds.top() + px(2.0));
     cx.simulate_mouse_down(at, MouseButton::Left, modifiers);
+    frames(cx);
     cx.simulate_mouse_up(at, MouseButton::Left, modifiers);
     cx.run_until_parked();
 }
 
+#[gpui::test]
+fn a_heading_written_above_with_the_same_title_is_not_the_pressed_one(cx: &mut TestAppContext) {
+    let text = "before\n\n[toc]\n\n# A\n\ntext\n\n## B\n";
+    let (document, cx) = open(text, MarkdownMode::Visual, cx);
+    type_in(&document, Some(0), Some("## B"), cx);
+    frames(cx);
+    press_entry(1, Modifiers::secondary_key(), cx);
+    let (caret, now) =
+        document.read_with(cx, |document, cx| (document.caret(cx), document.text(cx)));
+    assert_eq!(now, "## B\n\n[toc]\n\n# A\n\ntext\n\n## B\n");
+    assert_eq!(caret, (8, 0));
+}
+
+#[gpui::test]
+fn a_twin_typed_above_while_the_text_waits_is_not_the_pressed_one(cx: &mut TestAppContext) {
+    let (document, cx) = open(LISTED, MarkdownMode::Split, cx);
+    document.update(cx, |document, cx| {
+        document.editor.update(cx, |editor, cx| {
+            editor.edit([(0..0, "## B\n\n".to_string())], cx);
+        });
+    });
+    cx.run_until_parked();
+    assert!(!document.read_with(cx, |document, cx| document.read_now(cx)));
+    press_entry(1, Modifiers::none(), cx);
+    assert_eq!(
+        document.read_with(cx, |document, cx| document.caret(cx)),
+        (8, 0)
+    );
+}
+
+const TWINS: &str = "[toc]\n\n## B\n\ntext\n\n## B\n";
+
+/// Deletes the first twin while the text waits.
+fn delete_first_twin(document: &Entity<MarkdownDocument>, cx: &mut VisualTestContext) {
+    document.update(cx, |document, cx| {
+        document.editor.update(cx, |editor, cx| {
+            editor.edit([(7..13, String::new())], cx);
+        });
+    });
+    cx.run_until_parked();
+}
+
+#[gpui::test]
+fn a_deleted_twin_leaves_the_other_found(cx: &mut TestAppContext) {
+    let (document, cx) = open(TWINS, MarkdownMode::Split, cx);
+    delete_first_twin(&document, cx);
+    press_entry(1, Modifiers::none(), cx);
+    assert_eq!(
+        document.read_with(cx, |document, cx| document.caret(cx)),
+        (4, 0)
+    );
+}
+
+#[gpui::test]
+fn a_press_on_a_deleted_twin_moves_nothing(cx: &mut TestAppContext) {
+    let (document, cx) = open(TWINS, MarkdownMode::Split, cx);
+    delete_first_twin(&document, cx);
+    let before = document.read_with(cx, |document, cx| document.caret(cx));
+    press_entry(0, Modifiers::none(), cx);
+    assert_eq!(
+        document.read_with(cx, |document, cx| document.caret(cx)),
+        before
+    );
+}
+
 #[gpui::test]
 fn a_press_in_preview_reveals_the_heading(cx: &mut TestAppContext) {
     let (document, cx) = open(LISTED, MarkdownMode::Preview, cx);