Merge pull request #729 from kekingcn/copilot/fix-pdf-preview-error

Restore mobile PDF preview compatibility for browsers without `Array.prototype.at`

server/src/main/resources/static/pdfjs/build/pdf.worker.mjs

@@ -24,6 +24,7 @@
  * pdfjsVersion = 5.4.530
  * pdfjsBuild = 50cc4adac
  */
+import "../web/compatibility.mjs";
 /******/ var __webpack_modules__ = ({
 
 /***/ 34:

server/src/main/resources/static/pdfjs/web/compatibility.mjs

@@ -0,0 +1,42 @@
+const atTargets = [
+  Array,
+  String,
+  Int8Array,
+  Uint8Array,
+  Uint8ClampedArray,
+  Int16Array,
+  Uint16Array,
+  Int32Array,
+  Uint32Array,
+  Float32Array,
+  Float64Array,
+  globalThis.BigInt64Array,
+  globalThis.BigUint64Array,
+];
+
+function installAtPolyfill(target) {
+  if (!target?.prototype || typeof target.prototype.at === "function") {
+    return;
+  }
+  Object.defineProperty(target.prototype, "at", {
+    value(index) {
+      const length = this.length >>> 0;
+      let relativeIndex = Number(index);
+      if (Number.isNaN(relativeIndex)) {
+        relativeIndex = 0;
+      }
+      relativeIndex = Math.trunc(relativeIndex);
+      const resolvedIndex = relativeIndex >= 0 ? relativeIndex : length + relativeIndex;
+      if (resolvedIndex < 0 || resolvedIndex >= length) {
+        return undefined;
+      }
+      return this[resolvedIndex];
+    },
+    writable: true,
+    configurable: true,
+  });
+}
+
+for (const target of atTargets) {
+  installAtPolyfill(target);
+}

server/src/main/resources/static/pdfjs/web/viewer.html

@@ -29,6 +29,7 @@ See https://github.com/adobe-type-tools/cmap-resources
 
 <!-- This snippet is used in production (included from viewer.html) -->
 <link rel="resource" type="application/l10n" href="locale/locale.json" />
+<script src="compatibility.mjs" type="module"></script>
 <script src="../build/pdf.mjs" type="module"></script>
 
     <link rel="stylesheet" href="viewer.css" />

server/src/test/java/cn/keking/PdfViewerCompatibilityTests.java

@@ -0,0 +1,35 @@
+package cn.keking;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class PdfViewerCompatibilityTests {
+
+    @Test
+    void shouldLoadCompatibilityModuleBeforePdfJs() throws IOException {
+        String viewerHtml = readResource("/static/pdfjs/web/viewer.html");
+
+        assertTrue(viewerHtml.contains("<script src=\"compatibility.mjs\" type=\"module\"></script>"));
+        assertTrue(viewerHtml.indexOf("compatibility.mjs") < viewerHtml.indexOf("../build/pdf.mjs"));
+    }
+
+    @Test
+    void shouldLoadCompatibilityModuleInPdfWorker() throws IOException {
+        String workerScript = readResource("/static/pdfjs/build/pdf.worker.mjs");
+
+        assertTrue(workerScript.contains("import \"../web/compatibility.mjs\";"));
+    }
+
+    private String readResource(String resourcePath) throws IOException {
+        try (InputStream inputStream = getClass().getResourceAsStream(resourcePath)) {
+            assertNotNull(inputStream);
+            return new String(inputStream.readAllBytes(), StandardCharsets.UTF_8);
+        }
+    }
+}