Fix signature fields with widget children

src/core/document.js

@@ -2009,20 +2009,19 @@ class PDFDocument {
       if (!(field instanceof Dict)) {
         continue;
       }
+      if (isName(field.get("FT"), "Sig")) {
+        const sigDict = this.xref.fetchIfRef(field.get("V"));
+        if (sigDict instanceof Dict) {
+          const parsed = this.#parseSignatureDict(field, sigDict, fieldRef);
+          if (parsed) {
+            out.push(parsed);
+          }
+        }
+      }
       if (field.has("Kids")) {
+        // A terminal field can have Widget annotations as children, so its
+        // own signature must be collected before walking the field tree.
         this.#collectSignatureFields(field.get("Kids"), out, visitedRefs);
-        continue;
-      }
-      if (!isName(field.get("FT"), "Sig")) {
-        continue;
-      }
-      const sigDict = this.xref.fetchIfRef(field.get("V"));
-      if (!(sigDict instanceof Dict)) {
-        continue;
-      }
-      const parsed = this.#parseSignatureDict(field, sigDict, fieldRef);
-      if (parsed) {
-        out.push(parsed);
       }
     }
   }

test/unit/document_spec.js

@@ -312,6 +312,39 @@ describe("document", function () {
         expect(signatures[0].signerName).toEqual("John Smith");
       });
 
+      it("extracts signature fields with Widget children", async function () {
+        const acroForm = new Dict();
+        acroForm.set("SigFlags", 3);
+
+        const sigRef = Ref.get(33, 0);
+        const sigFieldRef = Ref.get(34, 0);
+        const widgetRef = Ref.get(35, 0);
+
+        const sigDict = makeSigDict({
+          byteRange: [0, 50, 100, 150],
+          name: "Alice",
+        });
+        const sigField = makeSigField({ T: "sig_alice", sigRef });
+        sigField.set("Kids", [widgetRef]);
+
+        const widget = new Dict();
+        widget.set("Subtype", Name.get("Widget"));
+        widget.set("Parent", sigFieldRef);
+
+        const xref = new XRefMock([
+          { ref: sigRef, data: sigDict },
+          { ref: sigFieldRef, data: sigField },
+          { ref: widgetRef, data: widget },
+        ]);
+        acroForm.set("Fields", [sigFieldRef]);
+
+        const pdfDocument = getDocument(acroForm, xref);
+        const signatures = await pdfDocument.signatures;
+        expect(signatures.length).toEqual(1);
+        expect(signatures[0].fieldName).toEqual("sig_alice");
+        expect(signatures[0].signerName).toEqual("Alice");
+      });
+
       it("skips signatures with malformed ByteRange", async function () {
         const acroForm = new Dict();
         acroForm.set("SigFlags", 3);