[api-minor] Remove the, in legacy builds, bundled ReadableStream polyfill

According to the MDN compatibility data, see https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream#browser_compatibility, all browsers that we support have native `ReadableStream` implementations (since quite some time too).

Hence only Node.js is now lagging behind w.r.t. `ReadableStream` support, and its experimental implementation doesn't really help us given the life-span of the LTS releases (see https://en.wikipedia.org/wiki/Node.js#Releases).
It seems quite unfortunate to bundle a `ReadableStream` polyfill in the `legacy` builds when it's unnecessary in browsers, given its overall size, but fortunately we can avoid that by simply listing `web-streams-polyfill` as a dependency for the `pdfjs-dist` library.

Author: Snuffleupagus

README.md

@@ -24,8 +24,8 @@ Feel free to stop by our [Matrix room](https://chat.mozilla.org/#/room/#pdfjs:mo
 ### Online demo
 
 Please note that the "Modern browsers" version assumes native support for
-features such as e.g. `async`/`await`, `ReadableStream`, optional chaining,
-nullish coalescing, and private `class` fields/methods.
+features such as `async`/`await`, optional chaining, nullish coalescing,
+and private `class` fields/methods.
 
 + Modern browsers: https://mozilla.github.io/pdf.js/web/viewer.html
 

external/dist/README.md

@@ -8,8 +8,7 @@ This is a pre-built version of the PDF.js source code. It is automatically
 generated by the build scripts.
 
 For usage with older browsers or environments, without support for modern
-features such as e.g. `async`/`await`, `ReadableStream`, optional chaining,
-nullish coalescing, and private `class` fields/methods; please see the `legacy`
-folder.
+features such as `async`/`await`, optional chaining, nullish coalescing,
+and private `class` fields/methods; please see the `legacy/` folder.
 
 See https://github.com/mozilla/pdf.js for learning and contributing.

gulpfile.js

@@ -2042,6 +2042,9 @@ function packageBowerJson() {
     homepage: DIST_HOMEPAGE,
     bugs: DIST_BUGS_URL,
     license: DIST_LICENSE,
+    dependencies: {
+      "web-streams-polyfill": "^3.2.0",
+    },
     peerDependencies: {
       "worker-loader": "^3.0.8", // Used in `external/dist/webpack.js`.
     },

src/core/worker.js

@@ -133,15 +133,15 @@ class WorkerMessageHandler {
       // Ensure that (primarily) Node.js users won't accidentally attempt to use
       // a non-translated/non-polyfilled build of the library, since that would
       // quickly fail anyway because of missing functionality.
-      if (
-        (typeof PDFJSDev === "undefined" || PDFJSDev.test("SKIP_BABEL")) &&
-        typeof ReadableStream === "undefined"
-      ) {
-        throw new Error(
+      if (typeof ReadableStream === "undefined") {
+        const partialMsg =
           "The browser/environment lacks native support for critical " +
-            "functionality used by the PDF.js library (e.g. `ReadableStream`); " +
-            "please use a `legacy`-build instead."
-        );
+          "functionality used by the PDF.js library (e.g. `ReadableStream`); ";
+
+        if (isNodeJS) {
+          throw new Error(partialMsg + "please use a `legacy`-build instead.");
+        }
+        throw new Error(partialMsg + "please update to a supported browser.");
       }
     }
 

src/shared/compatibility.js

@@ -12,6 +12,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+/* globals __non_webpack_require__ */
 
 import { isNodeJS } from "./is_node.js";
 
@@ -69,21 +70,12 @@ if (
 
   // Support: Node.js
   (function checkReadableStream() {
-    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("IMAGE_DECODERS")) {
-      // The current image decoders are synchronous, hence `ReadableStream`
-      // shouldn't need to be polyfilled for the IMAGE_DECODERS build target.
-      return;
-    }
-    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("CHROME")) {
-      // Slightly reduce the size of the Chromium-extension, given
-      // that `ReadableStream` has been supported since Chrome 43.
-      return;
-    }
     if (globalThis.ReadableStream || !isNodeJS) {
       return;
     }
-    globalThis.ReadableStream =
-      require("web-streams-polyfill/dist/ponyfill.js").ReadableStream;
+    globalThis.ReadableStream = __non_webpack_require__(
+      "web-streams-polyfill/dist/ponyfill.js"
+    ).ReadableStream;
   })();
 
   // Support: Firefox<94, Chrome<98, Safari, Node.js<17.0.0