Fix name tree keys being sorted by locale instead of by their bytes

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ### Unreleased
 
+- Fix links to a named destination going nowhere in readers that look the name up in sorted order, such as Chrome (PDFium) and qpdf, because name tree keys were sorted by locale with `localeCompare` instead of by their bytes: with destinations named `appendix` and `Chapter1`, `Chapter1` was written second and could not be found. The keys of the `EmbeddedFiles` and `JavaScript` name trees are sorted the same way
 - Escape document information in XMP metadata and omit characters XML 1.0 cannot represent, without changing the PDF Info dictionary. Fixes #1817
 - Fix text in a standard font garbling or dropping the characters after a tab, a carriage return or any other character code below `0x10`, which was written into the hex string of the text as a single digit, so the following digits paired up wrongly: a `\r` before a line break showed as `Ð`, and `Tab\there` was read back as `Tab–†W&P`. Fixes #1425, #606
 - Reuse the glyph width and kerning tables of a standard font across documents instead of building them again for every document that uses it, which made a short document using two standard fonts more than twice as slow to create

lib/name_tree.js

@@ -6,7 +6,10 @@ import PDFTree from './tree';
 
 class PDFNameTree extends PDFTree {
   _compareKeys(a, b) {
-    return a.localeCompare(b);
+    // Readers look a key up expecting the keys in ascending byte order
+    // (ISO 32000-1, 7.9.6). Character codes compare in that order for ASCII
+    // keys, while `localeCompare` puts `appendix` before `Chapter1`.
+    return a < b ? -1 : a > b ? 1 : 0;
   }
 
   _keysName() {

tests/unit/tree.spec.js

@@ -73,6 +73,24 @@ describe.each([
   });
 });
 
+describe('PDFNameTree key order', () => {
+  test('sorts the keys by their bytes rather than by locale', () => {
+    const tree = new PDFNameTree();
+    tree.add('appendix', new String('one'));
+    tree.add('Chapter1', new String('two'));
+
+    // readers look keys up in byte order, in which `Chapter1` (0x43) comes
+    // before `appendix` (0x61); in locale order they could not find it
+    expect(PDFObject.convert(tree)).toEqual(`<<
+  /Limits [(Chapter1) (appendix)]
+  /Names [
+    (Chapter1) (two)
+    (appendix) (one)
+]
+>>`);
+  });
+});
+
 describe('name trees in a document', () => {
   const names = ['(heading)', '(data.txt)', 'app.alert'];