fix: skip omitted diff lines instead of expanding excerpts during navigation

tests/diff.rs

@@ -182,3 +182,141 @@ fn typed_diff_edits_unsaved_working_after_and_preserves_undo_on_explicit_close()
     assert_eq!(fixture.git(&["rev-parse", "HEAD"]), base);
     assert_eq!(fixture.git(&["status", "--porcelain"]), "M buffer.rs");
 }
+
+#[test]
+fn editable_diff_navigation_skips_omitted_lines_without_expanding_excerpts() {
+    use vamp::diff::DisplayRow;
+
+    let fixture = Fixture::new();
+    fixture.git(&["init", "-q"]);
+    let source = fixture.0.join("repo/context.txt");
+    let mut lines = (1..=100)
+        .map(|line| format!("line_{line:03} words"))
+        .collect::<Vec<_>>();
+    lines[49].clear(); // Hidden short lines must not clamp the visible caret column.
+    fs::write(&source, format!("{}\n", lines.join("\n"))).unwrap();
+    fixture.git(&["add", "context.txt"]);
+    fixture.git(&["commit", "-qm", "base"]);
+    let base = fixture.git(&["rev-parse", "HEAD"]);
+    lines[19] = "changed_020 words".into();
+    lines[79] = "changed_080 words".into();
+    let text = format!("{}\n", lines.join("\n"));
+    fs::write(&source, &text).unwrap();
+    let config = fixture.0.join("config.rb");
+    fs::write(&config, "Vamp.configure do |config|\n config.clipboard_mode = 'separate'\n config.diff_context_lines = 1\n config.diff_expand_lines = 2\n config.bind 'ctrl+f', config.core.down\n config.bind 'ctrl+b', config.core.up\nend\n").unwrap();
+    let mut session =
+        EditorSession::open(Some(source.clone()), vec!["text".into()], Some(&config)).unwrap();
+    session.execute("diff");
+    wait_until(&mut session, |session| {
+        session
+            .editor()
+            .diff()
+            .is_some_and(|diff| diff.catalog.is_some() && !diff.loading)
+    });
+    type_query(&mut session, &base);
+    session.handle(Input::Down);
+    session.handle(Input::Enter);
+    session.handle(Input::Enter);
+    wait_until(&mut session, |session| {
+        session
+            .editor()
+            .diff()
+            .is_some_and(|diff| diff.phase == Phase::View)
+    });
+    session.handle(Input::BackTab);
+    let shown = |session: &EditorSession| {
+        let diff = session.editor().diff().unwrap();
+        diff.display_rows
+            .iter()
+            .filter_map(|row| match *row {
+                DisplayRow::Line(index) => diff.rows[index].after,
+                DisplayRow::Fold { .. } => None,
+            })
+            .collect::<Vec<_>>()
+    };
+    let excerpts = vec![18, 19, 20, 78, 79, 80];
+    assert_eq!(shown(&session), excerpts);
+    assert_eq!(session.editor().cursor().row, 18);
+    type_query(&mut session, "5l");
+    for (keys, row) in [("2j", 20), ("j", 78), ("k", 20), ("3j", 80), ("5k", 18)] {
+        type_query(&mut session, keys);
+        assert_eq!(session.editor().cursor().row, row, "{keys}");
+        assert_eq!(session.editor().cursor().column, 5, "{keys}");
+        assert_eq!(shown(&session), excerpts, "{keys}");
+    }
+    for (keys, row) in [
+        ("gb", 80),
+        ("gt", 18),
+        ("2j$w", 78),
+        ("b", 20),
+        ("$2w", 78),
+        ("0B", 20),
+    ] {
+        type_query(&mut session, keys);
+        assert_eq!(session.editor().cursor().row, row, "{keys}");
+        assert_eq!(shown(&session), excerpts, "{keys}");
+    }
+    session.handle(Input::Ctrl('f'));
+    assert_eq!(session.editor().cursor().row, 78);
+    session.handle(Input::Ctrl('b'));
+    assert_eq!(session.editor().cursor().row, 20);
+    type_query(&mut session, "Vj");
+    assert_eq!(session.editor().cursor().row, 78);
+    session.handle(Input::Escape);
+    session.handle(Input::Ctrl('k'));
+    assert_eq!(
+        session
+            .editor()
+            .carets()
+            .iter()
+            .map(|caret| caret.row)
+            .collect::<Vec<_>>(),
+        [20, 78]
+    );
+    type_query(&mut session, "j");
+    assert_eq!(
+        session
+            .editor()
+            .carets()
+            .iter()
+            .map(|caret| caret.row)
+            .collect::<Vec<_>>(),
+        [78, 79]
+    );
+    session.handle(Input::Escape);
+    type_query(&mut session, "gt2j$v");
+    session.handle(Input::Ctrl('a'));
+    assert_eq!(
+        session
+            .editor()
+            .carets()
+            .iter()
+            .map(|caret| caret.row)
+            .collect::<Vec<_>>(),
+        excerpts
+    );
+    assert_eq!(shown(&session), excerpts);
+    session.handle(Input::Escape);
+    session.handle(Input::Escape);
+    type_query(&mut session, "/line_040");
+    session.handle(Input::Enter);
+    assert_eq!(session.editor().cursor().row, 20);
+    type_query(&mut session, "/line_079");
+    session.handle(Input::Enter);
+    assert_eq!(session.editor().cursor().row, 78);
+    assert_eq!(shown(&session), excerpts);
+    type_query(&mut session, "gt2ji");
+    session.handle(Input::Down);
+    assert_eq!(session.editor().cursor().row, 78);
+    session.handle(Input::Up);
+    assert_eq!(session.editor().cursor().row, 20);
+    session.handle(Input::Escape);
+    assert_eq!(shown(&session), excerpts);
+    assert_eq!(session.editor().context().text, text);
+    assert!(!session.editor().dirty());
+    assert_eq!(fs::read_to_string(&source).unwrap(), text);
+    type_query(&mut session, "[");
+    assert_eq!(shown(&session), [16, 17, 18, 19, 20, 78, 79, 80]);
+    type_query(&mut session, "]");
+    assert_eq!(shown(&session), [16, 17, 18, 19, 20, 21, 22, 78, 79, 80]);
+}