From 15036a71138c6a1e6595548d7b9809bc845dd6c2 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Sun, 12 Apr 2020 16:29:31 +0200
Subject: [PATCH] [api-minor] Fix the return value of
 `PDFDocumentProxy.getViewerPreferences` when no viewer preferences are
 present (PR 10738 follow-up)

This patch fixes yet another instalment in the never-ending series of "what the *bleep* was I thinking", by changing the `PDFDocumentProxy.getViewerPreferences` method to return `null` by default.
Not only is this method now consistent with many other API methods, for the data not present case, but it also avoids having to e.g. loop through an object to check if it's actually empty (note the old unit-test).
---
 src/core/obj.js       | 5 ++++-
 src/display/api.js    | 3 ++-
 test/unit/api_spec.js | 5 +----
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/core/obj.js b/src/core/obj.js
index f8a820b6236e4c..c4a376af8cec43 100644
--- a/src/core/obj.js
+++ b/src/core/obj.js
@@ -479,7 +479,7 @@ class Catalog {
     };
 
     const obj = this.catDict.get("ViewerPreferences");
-    const prefs = Object.create(null);
+    let prefs = null;
 
     if (isDict(obj)) {
       for (const key in ViewerPreferencesValidators) {
@@ -583,6 +583,9 @@ class Catalog {
         }
 
         if (prefValue !== undefined) {
+          if (!prefs) {
+            prefs = Object.create(null);
+          }
           prefs[key] = prefValue;
         } else {
           info(`Bad value in ViewerPreferences for "${key}".`);
diff --git a/src/display/api.js b/src/display/api.js
index 8921cc690f1b49..91a219e3ba0ebe 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -663,7 +663,8 @@ class PDFDocumentProxy {
 
   /**
    * @returns {Promise} A promise that is resolved with an {Object} containing
-   *   the viewer preferences.
+   *   the viewer preferences, or `null` when no viewer preferences are present
+   *   in the PDF file.
    */
   getViewerPreferences() {
     return this._transport.getViewerPreferences();
diff --git a/test/unit/api_spec.js b/test/unit/api_spec.js
index 3c7b649041c837..7e893c32b9b0bd 100644
--- a/test/unit/api_spec.js
+++ b/test/unit/api_spec.js
@@ -24,7 +24,6 @@ import {
   createPromiseCapability,
   FontType,
   InvalidPDFException,
-  isEmptyObj,
   MissingPDFException,
   OPS,
   PasswordException,
@@ -846,9 +845,7 @@ describe("api", function() {
           return pdfDoc.getViewerPreferences();
         })
         .then(function(prefs) {
-          expect(
-            typeof prefs === "object" && prefs !== null && isEmptyObj(prefs)
-          ).toEqual(true);
+          expect(prefs).toEqual(null);
 
           loadingTask.destroy().then(done);
         })