Avoid mutating source widget parents

src/core/editor/pdf_editor.js

@@ -263,7 +263,7 @@ class PDFEditor {
   ) {
     if (obj instanceof Ref) {
       const {
-        currentDocument: { oldRefMapping },
+        currentDocument: { fieldToParent, oldRefMapping },
       } = this;
       const existingRef = oldRefMapping.get(obj);
       if (existingRef) {
@@ -299,9 +299,17 @@ class PDFEditor {
         }
       }
 
+      let cloneSource = true;
+      if (fieldToParent.has(oldRef) && obj instanceof Dict) {
+        // Avoid following a widget's field hierarchy while cloning the page,
+        // without mutating the source dictionary cached by its XRef.
+        obj = this.cloneDict(obj);
+        obj.delete("Parent");
+        cloneSource = false;
+      }
       this.xref[newRef.num] = await this.#collectDependencies(
         obj,
-        true,
+        cloneSource,
         xref,
         resourceStreamPath
       );
@@ -1223,11 +1231,8 @@ class PDFEditor {
                 "Sig"
               );
               const parentRef = annotationDict.getRaw("Parent") || null;
-              // We remove the parent to avoid visiting it when cloning the
+              // The parent will be omitted from the annotation clone to avoid
-              // annotation.
+              // visiting it, then restored by #mergeAcroForms.
-              // It'll be fixed later in #mergeAcroForms when merging the
-              // AcroForms.
-              annotationDict.delete("Parent");
               fieldToParent.put(annotationRef, parentRef);
             }
 

test/unit/api_spec.js

@@ -7671,6 +7671,36 @@ small scripts as well as for`);
         return fontIndex < 0 ? null : operatorList.argsArray[fontIndex][0];
       };
 
+      it("does not mutate source widget parents", async function () {
+        const pdfData = assemblePdf([
+          "1 0 obj\n<< /Type /Catalog /Pages 2 0 R " +
+            "/AcroForm 6 0 R >>\nendobj\n",
+          "2 0 obj\n<< /Type /Pages /Kids [3 0 R] /Count 1 >>\nendobj\n",
+          "3 0 obj\n<< /Type /Page /Parent 2 0 R " +
+            "/MediaBox [0 0 100 100] /Annots [4 0 R] >>\nendobj\n",
+          "4 0 obj\n<< /Type /Annot /Subtype /Widget /Rect [0 0 20 10] " +
+            "/Parent 5 0 R >>\nendobj\n",
+          "5 0 obj\n<< /FT /Tx /T (group) /Kids [4 0 R] >>\nendobj\n",
+          "6 0 obj\n<< /Fields [] /DA (/Helv 10 Tf) >>\nendobj\n",
+        ]);
+
+        let loadingTask = getDocument({ data: pdfData });
+        let pdfDoc = await loadingTask.promise;
+        const data = await pdfDoc.extractPages([{ document: null }]);
+
+        const sourceAnnotations = await (
+          await pdfDoc.getPage(1)
+        ).getAnnotations();
+        expect(sourceAnnotations[0].fieldName).toEqual("group");
+        expect(sourceAnnotations[0].fieldType).toEqual("Tx");
+        await loadingTask.destroy();
+
+        loadingTask = getDocument({ data });
+        pdfDoc = await loadingTask.promise;
+        expect(pdfDoc.numPages).toEqual(1);
+        await loadingTask.destroy();
+      });
+
       it("rebuilds a missing AcroForm Fields array", async function () {
         const data = assemblePdf([
           "1 0 obj\n<< /Type /Catalog /Pages 2 0 R /AcroForm 6 0 R >>\nendobj\n",