SVG: a Preserve Editing SVG reopened from disk saves as the full document again (#3867)

crates/engine/src/cmd/fileio/load.rs

@@ -454,6 +454,11 @@ fn open_loaded(s: &mut Session, loaded: Loaded, links: Resolved, path: Option<St
     let st = s.doc_mut()?;
     if saves_back {
         st.format = format.id;
+        // An SVG that reopened as the full document saves as one again: Save keeps Preserve
+        // Editing, as it would after a save of this session (#3867).
+        if restored && matches!(format.id, "svg" | "svgz") {
+            st.save_options.insert("preserveEditing".into(), json!(true));
+        }
     }
     st.converted = converted;
     st.imported_from = source_path;

crates/engine/src/cmd/fileio/tests_svg.rs

@@ -162,6 +162,24 @@ fn saving_several_artboards_as_plain_svg_warns_they_are_lost() {
     assert_eq!(artboards(&session(1).execute("document.save", &json!({"format": "svg"})).unwrap()), 0);
 }
 
+/// #3867: a Preserve Editing SVG opened from disk and saved with plain Save keeps the full
+/// document (every artboard), not just the artwork of the first.
+#[test]
+fn reopened_preserve_editing_svg_saves_as_the_full_document() {
+    let dir = tmp_dir("reopen");
+    let path = dir.join("keep.svg").to_string_lossy().to_string();
+    session(3).execute("document.save", &json!({"path": path, "svg": {"preserveEditing": true}})).unwrap();
+    let mut s = Session::new();
+    s.execute("document.open", &json!({"path": path})).unwrap();
+    assert_eq!(s.doc().unwrap().doc.artboards.len(), 3);
+    s.execute("document.save", &json!({})).unwrap();
+    let mut t = Session::new();
+    let r = t.execute("document.open", &json!({"path": path})).unwrap();
+    assert_eq!(r["restored"], json!(true), "{r}");
+    assert_eq!(t.doc().unwrap().doc.artboards.len(), 3, "every artboard survives open and Save");
+    let _ = std::fs::remove_dir_all(dir);
+}
+
 #[test]
 fn save_writes_svg_and_remembers_its_options() {
     let mut s = session(1);