fix: preserve review comments across unrelated edits

tests/unit/review.rs

@@ -67,13 +67,18 @@ fn database_restarts_preserve_identity_and_exact_stale_anchors() {
     assert_eq!(loaded.comments, review.comments);
     assert_eq!(loaded.reviewed_files, review.reviewed_files);
     assert_eq!(loaded.verdict, review.verdict);
-    assert!(!loaded.comments[0].anchor.matches_lines(
-        "working:new-snapshot",
-        Path::new("日本語.rs"),
-        Side::Before,
-        &["changed".into()],
-        true,
-    ));
+    assert!(
+        loaded.comments[0]
+            .anchor
+            .mapped_range(
+                "working:new-snapshot",
+                Path::new("日本語.rs"),
+                Side::Before,
+                &["changed".into()],
+                true,
+            )
+            .is_none()
+    );
     let path = root.join("export.json");
     loaded.save(&path).unwrap();
     let exported = fs::read(&path).unwrap();
@@ -387,6 +392,92 @@ fn default_directory_uses_absolute_xdg_then_absolute_home() {
     assert!(resolve(None, Some("")).is_err());
 }
 
+#[test]
+fn anchor_survives_unrelated_edit() {
+    let anchor = Anchor {
+        revision: "working:old".into(),
+        path: "source.rs".into(),
+        side: Side::After,
+        start: crate::plugin::TextPosition { row: 1, column: 0 },
+        end: crate::plugin::TextPosition { row: 1, column: 6 },
+        content: "before\ntarget\nafter\n".into(),
+    };
+    let map = |text: &str| {
+        anchor.mapped_range(
+            "working:new",
+            Path::new("source.rs"),
+            Side::After,
+            &text
+                .trim_end_matches('\n')
+                .split('\n')
+                .map(str::to_owned)
+                .collect::<Vec<_>>(),
+            text.ends_with('\n'),
+        )
+    };
+    assert_eq!(
+        map("changed\ntarget\nafter\n"),
+        Some(anchor.start..anchor.end)
+    );
+    assert_eq!(
+        map("inserted\nbefore\ntarget\nafter\n"),
+        Some(
+            crate::plugin::TextPosition { row: 2, column: 0 }..crate::plugin::TextPosition {
+                row: 2,
+                column: 6
+            }
+        )
+    );
+    assert!(map("before\ntargEt\nafter\n").is_none());
+    assert!(map("before\nafter\n").is_none());
+    assert!(map("before\ntarget\nafter\nbefore\ntarget\nafter\n").is_none());
+    assert_eq!(map("target\nbefore\ntarget\nafter\n").unwrap().start.row, 2);
+    assert_eq!(anchor.content, "before\ntarget\nafter\n");
+    let partial = Anchor {
+        content: "header\r\nprefix 👩‍💻e\u{301} suffix\r\nfooter\r\n".into(),
+        start: crate::plugin::TextPosition { row: 1, column: 7 },
+        end: crate::plugin::TextPosition { row: 1, column: 9 },
+        ..anchor.clone()
+    };
+    let moved = partial
+        .mapped_range(
+            "working:new",
+            Path::new("source.rs"),
+            Side::After,
+            &[
+                "inserted\r".into(),
+                "header\r".into(),
+                "longer prefix 👩‍💻e\u{301} suffix\r".into(),
+                "footer\r".into(),
+            ],
+            true,
+        )
+        .unwrap();
+    assert_eq!(
+        moved.start,
+        crate::plugin::TextPosition { row: 2, column: 14 }
+    );
+    assert_eq!(
+        moved.end,
+        crate::plugin::TextPosition { row: 2, column: 16 }
+    );
+    assert!(
+        partial
+            .mapped_range(
+                "other-commit",
+                Path::new("source.rs"),
+                Side::After,
+                &[
+                    "header\r".into(),
+                    "prefix 👩‍💻e\u{301} suffix\r".into(),
+                    "footer\r".into()
+                ],
+                true
+            )
+            .is_none()
+    );
+}
+
 #[test]
 fn persistence_validates_anchors_and_preserves_files_on_failure() {
     let directory = directory();
@@ -413,27 +504,39 @@ fn persistence_validates_anchors_and_preserves_files_on_failure() {
     assert_eq!(loaded.comments, review.comments);
     assert_eq!(loaded.verdict, review.verdict);
     let anchor = &loaded.comments[0].anchor;
-    assert!(!anchor.matches_lines(
-        "working:other",
-        Path::new("source.rs"),
-        Side::After,
-        &["first".into(), "last".into()],
-        true
-    ));
-    assert!(anchor.matches_lines(
-        "working:immutable",
-        Path::new("source.rs"),
-        Side::After,
-        &["first".into(), "last".into()],
-        true
-    ));
-    assert!(!anchor.matches_lines(
-        "working:immutable",
-        Path::new("source.rs"),
-        Side::After,
-        &["first".into(), "last".into()],
-        false
-    ));
+    assert!(
+        anchor
+            .mapped_range(
+                "working:other",
+                Path::new("source.rs"),
+                Side::After,
+                &["first".into(), "last".into()],
+                true
+            )
+            .is_some()
+    );
+    assert!(
+        anchor
+            .mapped_range(
+                "working:immutable",
+                Path::new("source.rs"),
+                Side::After,
+                &["first".into(), "last".into()],
+                true
+            )
+            .is_some()
+    );
+    assert!(
+        anchor
+            .mapped_range(
+                "working:immutable",
+                Path::new("source.rs"),
+                Side::After,
+                &["first".into(), "last".into()],
+                false
+            )
+            .is_none()
+    );
     loaded.summary = "Updated".into();
     loaded.save(&path).unwrap();
     assert_eq!(Review::load(&path, &root).unwrap().summary, "Updated");