Use a Map, rather than an Object, internally in the Catalog.openAction getter (PR 11644 follow-up)

src/core/obj.js

@@ -25,6 +25,7 @@ import {
   isBool,
   isNum,
   isString,
+  objectFromEntries,
   PermissionFlag,
   shadow,
   stringToPDFString,
@@ -786,7 +787,7 @@ class Catalog {
    */
   get openAction() {
     const obj = this._catDict.get("OpenAction");
-    let openAction = null;
+    const openActionMap = new Map();
 
     if (isDict(obj)) {
       // Convert the OpenAction dictionary into a format that works with
@@ -798,23 +799,18 @@ class Catalog {
       Catalog.parseDestDictionary({ destDict, resultObj });
 
       if (Array.isArray(resultObj.dest)) {
-        if (!openAction) {
-          openAction = Object.create(null);
-        }
-        openAction.dest = resultObj.dest;
+        openActionMap.set("dest", resultObj.dest);
       } else if (resultObj.action) {
-        if (!openAction) {
-          openAction = Object.create(null);
-        }
-        openAction.action = resultObj.action;
+        openActionMap.set("action", resultObj.action);
       }
     } else if (Array.isArray(obj)) {
-      if (!openAction) {
-        openAction = Object.create(null);
-      }
-      openAction.dest = obj;
+      openActionMap.set("dest", obj);
     }
-    return shadow(this, "openAction", openAction);
+    return shadow(
+      this,
+      "openAction",
+      openActionMap.size > 0 ? objectFromEntries(openActionMap) : null
+    );
   }
 
   get attachments() {

src/display/annotation_storage.js

@@ -13,6 +13,8 @@
  * limitations under the License.
  */
 
+import { objectFromEntries } from "../shared/util.js";
+
 /**
  * Key/value storage for annotation data in forms.
  */
@@ -67,7 +69,7 @@ class AnnotationStorage {
     if (this._storage.size === 0) {
       return null;
     }
-    return Object.fromEntries(this._storage);
+    return objectFromEntries(this._storage);
   }
 
   get size() {

src/display/metadata.js

@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-import { assert } from "../shared/util.js";
+import { assert, objectFromEntries } from "../shared/util.js";
 import { SimpleXMLParser } from "../shared/xml_parser.js";
 
 class Metadata {
@@ -118,7 +118,7 @@ class Metadata {
   }
 
   getAll() {
-    return Object.fromEntries(this._metadataMap);
+    return objectFromEntries(this._metadataMap);
   }
 
   has(name) {

src/display/optional_content_config.js

@@ -12,7 +12,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import { warn } from "../shared/util.js";
+import { objectFromEntries, warn } from "../shared/util.js";
 
 class OptionalContentGroup {
   constructor(name, intent) {
@@ -145,7 +145,7 @@ class OptionalContentConfig {
     if (!this._groups.size) {
       return null;
     }
-    return Object.fromEntries(this._groups);
+    return objectFromEntries(this._groups);
   }
 
   getGroup(id) {

src/shared/util.js

@@ -585,6 +585,11 @@ function string32(value) {
   );
 }
 
+// Ensures that the returned Object has a `null` prototype.
+function objectFromEntries(iterable) {
+  return Object.assign(Object.create(null), Object.fromEntries(iterable));
+}
+
 // Checks the endianness of the platform.
 function isLittleEndian() {
   const buffer8 = new Uint8Array(4);
@@ -1035,6 +1040,7 @@ export {
   isString,
   isSameOrigin,
   createValidAbsoluteUrl,
+  objectFromEntries,
   IsLittleEndianCached,
   IsEvalSupportedCached,
   removeNullCharacters,