Fix annotation border style parsing by handling empty dash arrays

The PDF specification states that empty dash arrays, i.e. arrays with
zero elements, are in fact valid. In that case the dash array simply
corresponds to a solid, unbroken line. However, this case was erroneously
being flagged as invalid and therefore the annotation was not drawn
because its width was set to zero. This commit fixes the issue by
allowing dash arrays to have a length of zero.

src/core/annotation.js

@@ -1474,9 +1474,9 @@ class AnnotationBorderStyle {
     // We validate the dash array, but we do not use it because CSS does not
     // allow us to change spacing of dashes. For more information, visit
     // http://www.w3.org/TR/css3-background/#the-border-style.
-    if (Array.isArray(dashArray) && dashArray.length > 0) {
-      // According to the PDF specification: the elements in `dashArray`
-      // shall be numbers that are nonnegative and not all equal to zero.
+    if (Array.isArray(dashArray)) {
+      // The PDF specification states that elements in the dash array, if
+      // present, must be non-negative numbers and must not all equal zero.
       let isValid = true;
       let allZeros = true;
       for (const element of dashArray) {
@@ -1488,7 +1488,7 @@ class AnnotationBorderStyle {
           allZeros = false;
         }
       }
-      if (isValid && !allZeros) {
+      if (dashArray.length === 0 || (isValid && !allZeros)) {
         this.dashArray = dashArray;
 
         if (forceStyle) {

test/pdfs/.gitignore

@@ -514,6 +514,7 @@
 !issue11549_reduced.pdf
 !issue8097_reduced.pdf
 !issue15262.pdf
+!issue17904.pdf
 !bug1743245.pdf
 !quadpoints.pdf
 !transparent.pdf

test/test_manifest.json

@@ -3858,6 +3858,14 @@
     "type": "eq",
     "annotations": true
   },
+  {
+    "id": "issue17904",
+    "file": "pdfs/issue17904.pdf",
+    "md5": "4b8f0b565a61bf068ef72d232c997cef",
+    "rounds": 1,
+    "type": "eq",
+    "annotations": true
+  },
   {
     "id": "issue6179_reduced",
     "file": "pdfs/issue6179_reduced.pdf",

test/unit/annotation_spec.js

@@ -549,6 +549,15 @@ describe("annotation", function () {
       expect(borderStyle.dashArray).toEqual([3]);
     });
 
+    it("should not set the width to zero if the dash array is empty (issue 17904)", function () {
+      const borderStyle = new AnnotationBorderStyle();
+      borderStyle.setWidth(3);
+      borderStyle.setDashArray([]);
+
+      expect(borderStyle.width).toEqual(3);
+      expect(borderStyle.dashArray).toEqual([]);
+    });
+
     it("should set and get a valid horizontal corner radius", function () {
       const borderStyle = new AnnotationBorderStyle();
       borderStyle.setHorizontalCornerRadius(3);