Use alternate method to get document fingerprint

`PDFViewerApplication.documentFingerprint` was removed in recent
versions of PDF.js [1]. This issue causes loading the bookmarklet into
Firefox 63+ to fail because the client thinks the PDF is still loading.

`PDFViewerApplication.pdfDocument.fingerprint` is the replacement
mentioned in the commit that removed the property and it also appears to
be more clearly a part of PDF.js' documented API.

This change is backwards-compatible with the version of PDF.js that
currently ships with Via.

[1] https://github.com/mozilla/pdf.js/commit/e522b2d87e8eb3d4eb8a391a098a0f6f157e8c12

src/annotator/plugin/pdf-metadata.js

@@ -41,7 +41,7 @@ class PDFMetadata {
         resolve(app);
       };
 
-      if (app.documentFingerprint) {
+      if (app.downloadComplete) {
         resolve(app);
       } else {
         window.addEventListener('documentload', finish);
@@ -61,7 +61,7 @@ class PDFMetadata {
     return this._loaded.then(app => {
       let uri = getPDFURL(app);
       if (!uri) {
-        uri = fingerprintToURN(app.documentFingerprint);
+        uri = fingerprintToURN(app.pdfDocument.fingerprint);
       }
       return uri;
     });
@@ -86,7 +86,7 @@ class PDFMetadata {
       }
 
       const link = [
-        {href: fingerprintToURN(app.documentFingerprint)},
+        {href: fingerprintToURN(app.pdfDocument.fingerprint)},
       ];
 
       const url = getPDFURL(app);
@@ -97,7 +97,7 @@ class PDFMetadata {
       return {
         title: title,
         link: link,
-        documentFingerprint: app.documentFingerprint,
+        documentFingerprint: app.pdfDocument.fingerprint,
       };
     });
   }

src/annotator/plugin/test/pdf-metadata-test.js

@@ -24,6 +24,15 @@ class FakeMetadata {
   }
 }
 
+/**
+ * Fake implementation of PDF.js `window.PDFViewerApplication.pdfDocument`.
+ */
+class FakePDFDocumentProxy {
+  constructor({ fingerprint }) {
+    this.fingerprint = fingerprint;
+  }
+}
+
 /**
  * Fake implementation of PDF.js `window.PDFViewerApplication` entry point.
  *
@@ -38,7 +47,7 @@ class FakePDFViewerApplication {
     this.url = url;
     this.documentInfo = undefined;
     this.metadata = undefined;
-    this.documentFingerprint = undefined;
+    this.pdfDocument = null;
   }
 
   /**
@@ -50,6 +59,7 @@ class FakePDFViewerApplication {
     window.dispatchEvent(event);
 
     this.url = url;
+    this.downloadComplete = true;
     this.documentInfo = {};
 
     if (typeof title !== undefined) {
@@ -60,9 +70,7 @@ class FakePDFViewerApplication {
       this.metadata = new FakeMetadata(metadata);
     }
 
-    // TODO - This property was removed in recent versions of PDF.js.
-    // The PDFMetadata class should use `pdfDocument.fingerprint` instead.
-    this.documentFingerprint = fingerprint;
+    this.pdfDocument = new FakePDFDocumentProxy({ fingerprint });
   }
 }
 
@@ -149,9 +157,9 @@ describe('annotator/plugin/pdf-metadata', function () {
       it('gets the title from the dc:title field', function () {
         const expectedMetadata = {
           title: 'dcFakeTitle',
-          link: [{href: 'urn:x-pdf:' + fakePDFViewerApplication.documentFingerprint},
+          link: [{href: 'urn:x-pdf:' + fakePDFViewerApplication.pdfDocument.fingerprint},
             {href: fakePDFViewerApplication.url}],
-          documentFingerprint: fakePDFViewerApplication.documentFingerprint,
+          documentFingerprint: fakePDFViewerApplication.pdfDocument.fingerprint,
         };
 
         return pdfMetadata.getMetadata().then(function (actualMetadata) {
@@ -162,9 +170,9 @@ describe('annotator/plugin/pdf-metadata', function () {
       it('gets the title from the documentInfo.Title field', function () {
         const expectedMetadata = {
           title: fakePDFViewerApplication.documentInfo.Title,
-          link: [{href: 'urn:x-pdf:' + fakePDFViewerApplication.documentFingerprint},
+          link: [{href: 'urn:x-pdf:' + fakePDFViewerApplication.pdfDocument.fingerprint},
             {href: fakePDFViewerApplication.url}],
-          documentFingerprint: fakePDFViewerApplication.documentFingerprint,
+          documentFingerprint: fakePDFViewerApplication.pdfDocument.fingerprint,
         };
 
         fakePDFViewerApplication.metadata.has = sinon.stub().returns(false);
@@ -182,7 +190,7 @@ describe('annotator/plugin/pdf-metadata', function () {
           url: 'file://fake.pdf',
         });
         const expectedMetadata = {
-          link: [{href: 'urn:x-pdf:' + fakePDFViewerApplication.documentFingerprint}],
+          link: [{href: 'urn:x-pdf:' + fakePDFViewerApplication.pdfDocument.fingerprint}],
         };
 
         pdfMetadata = new PDFMetadata(fakePDFViewerApplication);