Polyfill structuredClone with core-js (PR 13948 follow-up)

This allows us to remove the manually implemented `structuredClone` polyfill, thus reducing the maintenance burden for the `LoopbackPort` class; refer to https://github.com/zloirock/core-js#structuredclone

*Please note:* While `structuredClone` support landed already in Firefox 94, Google Chrome only added it in version 98 (currently in Beta). However, given that the `LoopbackPort` will only be used together with *fake workers* in browsers this shouldn't be too much of a problem.[1]
For Node.js environments, where *fake workers* are unfortunately necessary, using a `legacy/`-build is already required which thus guarantees that the `structuredClone` polyfill is available.

Also, the patch updates core-js to the latest version since that one includes `structuredClone` improvements; please see https://github.com/zloirock/core-js/releases/tag/v3.20.3

---
[1] Given that we only support browsers with proper worker support, if *fake workers* are being used that essentially indicates a configuration problem/error.

.eslintrc

@@ -28,6 +28,7 @@
   "globals": {
     "PDFJSDev": false,
     "exports": false,
+    "structuredClone": false,
     "SystemJS": false,
   },
 

package-lock.json

@@ -18,7 +18,7 @@
         "autoprefixer": "^10.4.2",
         "babel-loader": "^8.2.3",
         "canvas": "^2.9.0",
-        "core-js": "^3.20.2",
+        "core-js": "^3.20.3",
         "cross-env": "^7.0.3",
         "dommatrix": "^0.0.24",
         "es-module-shims": "^1.4.1",
@@ -3899,9 +3899,9 @@
       }
     },
     "node_modules/core-js": {
-      "version": "3.20.2",
+      "version": "3.20.3",
-      "resolved": "https://registry.npmjs.org/core-js/-/core-js-3.20.2.tgz",
+      "resolved": "https://registry.npmjs.org/core-js/-/core-js-3.20.3.tgz",
-      "integrity": "sha512-nuqhq11DcOAbFBV4zCbKeGbKQsUDRqTX0oqx7AttUBuqe3h20ixsE039QHelbL6P4h+9kytVqyEtyZ6gsiwEYw==",
+      "integrity": "sha512-vVl8j8ph6tRS3B8qir40H7yw7voy17xL0piAjlbBUsH7WIfzoedL/ZOr1OV9FyZQLWXsayOJyV4tnRyXR85/ag==",
       "dev": true,
       "hasInstallScript": true,
       "funding": {
@@ -12106,6 +12106,7 @@
     },
     "node_modules/npm/node_modules/lodash._baseindexof": {
       "version": "3.1.0",
+      "extraneous": true,
       "inBundle": true,
       "license": "MIT"
     },
@@ -12121,16 +12122,19 @@
     },
     "node_modules/npm/node_modules/lodash._bindcallback": {
       "version": "3.0.1",
+      "extraneous": true,
       "inBundle": true,
       "license": "MIT"
     },
     "node_modules/npm/node_modules/lodash._cacheindexof": {
       "version": "3.0.2",
+      "extraneous": true,
       "inBundle": true,
       "license": "MIT"
     },
     "node_modules/npm/node_modules/lodash._createcache": {
       "version": "3.1.2",
+      "extraneous": true,
       "inBundle": true,
       "license": "MIT",
       "dependencies": {
@@ -12145,6 +12149,7 @@
     },
     "node_modules/npm/node_modules/lodash._getnative": {
       "version": "3.9.1",
+      "extraneous": true,
       "inBundle": true,
       "license": "MIT"
     },
@@ -12162,6 +12167,7 @@
     },
     "node_modules/npm/node_modules/lodash.restparam": {
       "version": "3.6.1",
+      "extraneous": true,
       "inBundle": true,
       "license": "MIT"
     },
@@ -21554,9 +21560,9 @@
       }
     },
     "core-js": {
-      "version": "3.20.2",
+      "version": "3.20.3",
-      "resolved": "https://registry.npmjs.org/core-js/-/core-js-3.20.2.tgz",
+      "resolved": "https://registry.npmjs.org/core-js/-/core-js-3.20.3.tgz",
-      "integrity": "sha512-nuqhq11DcOAbFBV4zCbKeGbKQsUDRqTX0oqx7AttUBuqe3h20ixsE039QHelbL6P4h+9kytVqyEtyZ6gsiwEYw==",
+      "integrity": "sha512-vVl8j8ph6tRS3B8qir40H7yw7voy17xL0piAjlbBUsH7WIfzoedL/ZOr1OV9FyZQLWXsayOJyV4tnRyXR85/ag==",
       "dev": true
     },
     "core-js-compat": {
@@ -27927,7 +27933,8 @@
         },
         "lodash._baseindexof": {
           "version": "3.1.0",
-          "bundled": true
+          "bundled": true,
+          "extraneous": true
         },
         "lodash._baseuniq": {
           "version": "4.6.0",
@@ -27940,15 +27947,18 @@
         },
         "lodash._bindcallback": {
           "version": "3.0.1",
-          "bundled": true
+          "bundled": true,
+          "extraneous": true
         },
         "lodash._cacheindexof": {
           "version": "3.0.2",
-          "bundled": true
+          "bundled": true,
+          "extraneous": true
         },
         "lodash._createcache": {
           "version": "3.1.2",
           "bundled": true,
+          "extraneous": true,
           "requires": {
             "lodash._getnative": "^3.0.0"
           }
@@ -27960,7 +27970,8 @@
         },
         "lodash._getnative": {
           "version": "3.9.1",
-          "bundled": true
+          "bundled": true,
+          "extraneous": true
         },
         "lodash._root": {
           "version": "3.0.1",
@@ -27974,7 +27985,8 @@
         },
         "lodash.restparam": {
           "version": "3.6.1",
-          "bundled": true
+          "bundled": true,
+          "extraneous": true
         },
         "lodash.union": {
           "version": "4.6.0",

package.json

@@ -11,7 +11,7 @@
     "autoprefixer": "^10.4.2",
     "babel-loader": "^8.2.3",
     "canvas": "^2.9.0",
-    "core-js": "^3.20.2",
+    "core-js": "^3.20.3",
     "cross-env": "^7.0.3",
     "dommatrix": "^0.0.24",
     "es-module-shims": "^1.4.1",

src/display/api.js

@@ -1913,91 +1913,14 @@ class LoopbackPort {
   }
 
   postMessage(obj, transfers) {
-    function cloneValue(object) {
+    const event = {
-      if (
+      data:
-        (typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) ||
+        typeof PDFJSDev === "undefined" ||
-        globalThis.structuredClone
+        PDFJSDev.test("SKIP_BABEL") ||
-      ) {
+        transfers
-        return globalThis.structuredClone(object, transfers);
+          ? structuredClone(obj, transfers)
-      }
+          : structuredClone(obj),
-
+    };
-      // Trying to perform a structured clone close to the spec, including
-      // transfers.
-      function fallbackCloneValue(value) {
-        if (
-          typeof value === "function" ||
-          typeof value === "symbol" ||
-          value instanceof URL
-        ) {
-          throw new Error(
-            `LoopbackPort.postMessage - cannot clone: ${value?.toString()}`
-          );
-        }
-
-        if (typeof value !== "object" || value === null) {
-          return value;
-        }
-        if (cloned.has(value)) {
-          // already cloned the object
-          return cloned.get(value);
-        }
-        let buffer, result;
-        if ((buffer = value.buffer) && isArrayBuffer(buffer)) {
-          // We found object with ArrayBuffer (typed array).
-          if (transfers?.includes(buffer)) {
-            result = new value.constructor(
-              buffer,
-              value.byteOffset,
-              value.byteLength
-            );
-          } else {
-            result = new value.constructor(value);
-          }
-          cloned.set(value, result);
-          return result;
-        }
-        if (value instanceof Map) {
-          result = new Map();
-          cloned.set(value, result); // Adding to cache now for cyclic references.
-          for (const [key, val] of value) {
-            result.set(key, fallbackCloneValue(val));
-          }
-          return result;
-        }
-        if (value instanceof Set) {
-          result = new Set();
-          cloned.set(value, result); // Adding to cache now for cyclic references.
-          for (const val of value) {
-            result.add(fallbackCloneValue(val));
-          }
-          return result;
-        }
-        result = Array.isArray(value) ? [] : Object.create(null);
-        cloned.set(value, result); // Adding to cache now for cyclic references.
-        // Cloning all value and object properties, however ignoring properties
-        // defined via getter.
-        for (const i in value) {
-          let desc,
-            p = value;
-          while (!(desc = Object.getOwnPropertyDescriptor(p, i))) {
-            p = Object.getPrototypeOf(p);
-          }
-          if (typeof desc.value === "undefined") {
-            continue;
-          }
-          if (typeof desc.value === "function" && !value.hasOwnProperty?.(i)) {
-            continue;
-          }
-          result[i] = fallbackCloneValue(desc.value);
-        }
-        return result;
-      }
-
-      const cloned = new WeakMap();
-      return fallbackCloneValue(object);
-    }
-
-    const event = { data: cloneValue(obj) };
 
     this._deferred.then(() => {
       for (const listener of this._listeners) {

src/shared/compatibility.js

@@ -100,4 +100,17 @@ if (
     globalThis.ReadableStream =
       require("web-streams-polyfill/dist/ponyfill.js").ReadableStream;
   })();
+
+  // Support: Firefox<94, Chrome<98, Safari, Node.js<17.0.0
+  (function checkStructuredClone() {
+    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("IMAGE_DECODERS")) {
+      // The current image decoders are synchronous, hence `structuredClone`
+      // shouldn't need to be polyfilled for the IMAGE_DECODERS build target.
+      return;
+    }
+    if (globalThis.structuredClone) {
+      return;
+    }
+    require("core-js/web/structured-clone.js");
+  })();
 }