From b00835f58922705c9d1898d00baf2d9bde4e44c3 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Mon, 9 Dec 2019 15:00:45 +0100
Subject: [PATCH] Attempt to improve the `PDFDocument` error message for empty
 files (issue 5887)

Given that the error in question is surfaced on the API-side, this patch makes the following changes:
 - Updates the wording such that it'll hopefully be slightly easier for users to understand.
 - Changes the plain `Error` to an `InvalidPDFException` instead, since that should work better with the existing Error handling.
 - Adds a unit-test which loads an empty PDF document (and also improves a pre-existing `InvalidPDFException` message and its test-case).
---
 src/core/document.js  |  9 +++++----
 src/core/obj.js       |  2 +-
 test/unit/api_spec.js | 20 ++++++++++++++++++--
 3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/src/core/document.js b/src/core/document.js
index 1a4ee0418..e576fa90a 100644
--- a/src/core/document.js
+++ b/src/core/document.js
@@ -15,9 +15,9 @@
 /* eslint no-var: error */
 
 import {
-  assert, bytesToString, FormatError, info, isArrayBuffer, isArrayEqual, isBool,
-  isNum, isSpace, isString, OPS, shadow, stringToBytes, stringToPDFString, Util,
-  warn
+  assert, bytesToString, FormatError, info, InvalidPDFException, isArrayBuffer,
+  isArrayEqual, isBool, isNum, isSpace, isString, OPS, shadow, stringToBytes,
+  stringToPDFString, Util, warn
 } from '../shared/util';
 import { Catalog, ObjectLoader, XRef } from './obj';
 import { Dict, isDict, isName, isStream, Ref } from './primitives';
@@ -375,7 +375,8 @@ class PDFDocument {
       throw new Error('PDFDocument: Unknown argument type');
     }
     if (stream.length <= 0) {
-      throw new Error('PDFDocument: Stream must have data');
+      throw new InvalidPDFException(
+        'The PDF file is empty, i.e. its size is zero bytes.');
     }
 
     this.pdfManager = pdfManager;
diff --git a/src/core/obj.js b/src/core/obj.js
index 92a66abea..afa59bfd5 100644
--- a/src/core/obj.js
+++ b/src/core/obj.js
@@ -1519,7 +1519,7 @@ var XRef = (function XRefClosure() {
         return trailerDict;
       }
       // nothing helps
-      throw new InvalidPDFException('Invalid PDF structure');
+      throw new InvalidPDFException('Invalid PDF structure.');
     },
 
     readXRef: function XRef_readXRef(recoveryMode) {
diff --git a/test/unit/api_spec.js b/test/unit/api_spec.js
index 91eb5edf6..7731f5a37 100644
--- a/test/unit/api_spec.js
+++ b/test/unit/api_spec.js
@@ -148,8 +148,10 @@ describe('api', function() {
       var loadingTask = getDocument(buildGetDocumentParams('bug1020226.pdf'));
       loadingTask.promise.then(function () {
         done.fail('shall fail loading');
-      }).catch(function (error) {
-        expect(error instanceof InvalidPDFException).toEqual(true);
+      }).catch(function(reason) {
+        expect(reason instanceof InvalidPDFException).toEqual(true);
+        expect(reason.message).toEqual('Invalid PDF structure.');
+
         loadingTask.destroy().then(done);
       });
     });
@@ -292,6 +294,20 @@ describe('api', function() {
         done();
       }).catch(done.fail);
     });
+
+    it('creates pdf doc from empty typed array', function(done) {
+      const loadingTask = getDocument(new Uint8Array(0));
+
+      loadingTask.promise.then(function() {
+        done.fail('shall not open empty file');
+      }, function(reason) {
+        expect(reason instanceof InvalidPDFException);
+        expect(reason.message).toEqual(
+          'The PDF file is empty, i.e. its size is zero bytes.');
+
+        loadingTask.destroy().then(done);
+      });
+    });
   });
 
   describe('PDFWorker', function() {