[api-minor] Expose the /Desc-attribute of file attachments in the vie…

…wer (issue 18030)

In the viewer this will be displayed in the `title` of the hyperlink, which is probably the best we can do here given how the viewer is implemented.

src/core/file_spec.js

@@ -53,9 +53,9 @@ class FileSpec {
     if (root.has("FS")) {
       this.fs = root.get("FS");
     }
-    this.description = root.has("Desc")
-      ? stringToPDFString(root.get("Desc"))
-      : "";
+    const desc = root.get("Desc");
+    this.description =
+      desc && typeof desc === "string" ? stringToPDFString(desc) : null;
     if (root.has("RF")) {
       warn("Related file specifications are not supported");
     }
@@ -106,6 +106,7 @@ class FileSpec {
     return {
       filename: this.filename,
       content: this.content,
+      description: this.description,
     };
   }
 }

src/display/annotation_layer.js

@@ -857,6 +857,9 @@ class LinkAnnotationElement extends AnnotationElement {
    */
   #bindAttachment(link, attachment, dest = null) {
     link.href = this.linkService.getAnchorUrl("");
+    if (attachment.description) {
+      link.title = attachment.description;
+    }
     link.onclick = () => {
       this.downloadManager?.openOrDownloadData(
         attachment.content,

test/pdfs/.gitignore

@@ -54,6 +54,7 @@
 !issue17056.pdf
 !issue17679.pdf
 !issue17679_2.pdf
+!issue18030.pdf
 !issue14953.pdf
 !issue15367.pdf
 !issue15372.pdf

test/unit/annotation_spec.js

@@ -4005,7 +4005,7 @@ describe("annotation", function () {
       const fileSpecRef = Ref.get(19, 0);
       const fileSpecDict = new Dict();
       fileSpecDict.set("Type", Name.get("Filespec"));
-      fileSpecDict.set("Desc", "");
+      fileSpecDict.set("Desc", "abc");
       fileSpecDict.set("EF", embeddedFileDict);
       fileSpecDict.set("UF", "Test.txt");
 
@@ -4035,6 +4035,7 @@ describe("annotation", function () {
       expect(data.annotationType).toEqual(AnnotationType.FILEATTACHMENT);
       expect(data.file.filename).toEqual("Test.txt");
       expect(data.file.content).toEqual(stringToBytes("Test attachment"));
+      expect(data.file.description).toEqual("abc");
     });
   });
 

test/unit/api_spec.js

@@ -1475,11 +1475,28 @@ describe("api", function () {
       const pdfDoc = await loadingTask.promise;
       const attachments = await pdfDoc.getAttachments();
 
-      const attachment = attachments["foo.txt"];
-      expect(attachment.filename).toEqual("foo.txt");
-      expect(attachment.content).toEqual(
+      const { filename, content, description } = attachments["foo.txt"];
+      expect(filename).toEqual("foo.txt");
+      expect(content).toEqual(
         new Uint8Array([98, 97, 114, 32, 98, 97, 122, 32, 10])
       );
+      expect(description).toEqual(null);
+
+      await loadingTask.destroy();
+    });
+
+    it("gets attachments, with /Desc", async function () {
+      const loadingTask = getDocument(buildGetDocumentParams("issue18030.pdf"));
+      const pdfDoc = await loadingTask.promise;
+      const attachments = await pdfDoc.getAttachments();
+
+      const { filename, content, description } = attachments["empty.pdf"];
+      expect(filename).toEqual("Empty page.pdf");
+      expect(content instanceof Uint8Array).toEqual(true);
+      expect(content.length).toEqual(2357);
+      expect(description).toEqual(
+        "SHA512: 06bec56808f93846f1d41ff0be4e54079c1291b860378c801c0f35f1d127a8680923ff6de59bd5a9692f01f0d97ca4f26da178ed03635fa4813d86c58a6c981a"
+      );
 
       await loadingTask.destroy();
     });

web/pdf_attachment_viewer.js

@@ -94,7 +94,10 @@ class PDFAttachmentViewer extends BaseTreeViewer {
   /**
    * @protected
    */
-  _bindLink(element, { content, filename }) {
+  _bindLink(element, { content, filename, description }) {
+    if (description) {
+      element.title = description;
+    }
     element.onclick = () => {
       this.downloadManager.openOrDownloadData(content, filename);
       return false;
@@ -120,6 +123,7 @@ class PDFAttachmentViewer extends BaseTreeViewer {
     for (const name in attachments) {
       const item = attachments[name];
       const content = item.content,
+        description = item.description,
         filename = getFilenameFromUrl(
           item.filename,
           /* onlyStripPath = */ true
@@ -129,7 +133,7 @@ class PDFAttachmentViewer extends BaseTreeViewer {
       div.className = "treeItem";
 
       const element = document.createElement("a");
-      this._bindLink(element, { content, filename });
+      this._bindLink(element, { content, filename, description });
       element.textContent = this._normalizeTextContent(filename);
 
       div.append(element);