Fix PDF fallback when the preprint is not in the database

src/components/extension-fallback.js

@@ -66,6 +66,7 @@ export default function ExtensionFallback() {
           <Suspense fallback={<SuspenseLoading>Loading PDF</SuspenseLoading>}>
             <PdfViewer
               docId={preprintId}
+              pdfUrl={pdfUrl}
               loading={<SuspenseLoading>Loading PDF</SuspenseLoading>}
             />
           </Suspense>
@@ -80,6 +81,7 @@ export default function ExtensionFallback() {
             <Suspense fallback={<SuspenseLoading>Loading PDF</SuspenseLoading>}>
               <PdfViewer
                 docId={identifier}
+                pdfUrl={pdfUrl}
                 loading={<SuspenseLoading>Loading PDF</SuspenseLoading>}
               />
             </Suspense>

src/components/pdf-viewer.js

@@ -11,7 +11,7 @@ const CSS_MAX_WIDTH = 900; // keep in sync with CSS
  * This implement an infinite scroll mechanism so that we never load more than a
  * few pages at the time
  */
-export default function PdfViewer({ docId, loading }) {
+export default function PdfViewer({ docId, pdfUrl, loading }) {
   const containerEl = useRef(null);
   const getWidth = () => {
     const el = containerEl.current;
@@ -79,7 +79,7 @@ export default function PdfViewer({ docId, loading }) {
         <Document
           file={`${process.env.API_URL}/api/pdf?preprintId=${encodeURIComponent(
             docId
-          )}`}
+          )}${pdfUrl ? `&pdfUrl=${encodeURIComponent(pdfUrl)}` : ''}`}
           loading={loading}
           onLoadSuccess={async pdf => {
             let dims = [];

src/routes/api-routes.js

@@ -375,16 +375,21 @@ router.get(
  * due to cross origin restriction we need to proxy the PDF
  */
 router.get('/pdf', async (req, res, next) => {
-  let pdfUrl;
-  const preprintId = req.query.preprintId;
-  try {
-    const body = await req.db.get(`preprint:${preprintId}`);
-    pdfUrl = getPdfUrl(body);
-    if (!pdfUrl) {
-      return next(createError(500, `Could not determine PDF from prereview: ${JSON.stringify(body)}`));
+  let { preprintId, pdfUrl } = req.query;
+
+  // If we already have the pdfUrl, there's no need to look in the database.
+  // The pdfUrl is present in the case where the preprint is not in the database yet,
+  // but we were able to resolve it.
+  if (!pdfUrl) {
+    try {
+      const body = await req.db.get(`preprint:${preprintId}`);
+      pdfUrl = getPdfUrl(body);
+      if (!pdfUrl) {
+        return next(createError(500, `Could not determine PDF from prereview: ${JSON.stringify(body)}`));
+      }
+    } catch (err) {
+      return next(createError(500, `Prereview query failed: ${preprintId} ${JSON.stringify(err)}`));
     }
-  } catch (err) {
-    return next(createError(500, `Prereview query failed: ${preprintId} ${JSON.stringify(err)}`));
   }
 
   if (!pdfUrl) {