From 5ecd60b8a9ba3458b30a102fe74abed357ccae3d Mon Sep 17 00:00:00 2001
From: rmz-oz <262968088+rmz-oz@users.noreply.github.com>
Date: Mon, 28 Sep 2026 06:41:40 +0300
Subject: [PATCH] Keep encoded # in ZIM paths when building document URIs

A `%23` in the path or query of an original URL is decoded to a
literal `#` in the ZIM path, as expected. But get_document_uri() then
passed that ZIM path to urlsplit(), which treated the `#` as a fragment
delimiter and silently dropped everything after it. The rewritten link
therefore pointed to another (usually missing) ZIM entry, e.g.
`a/b%23c` was rewritten to `a/b`.

Tell urlsplit() not to look for a fragment: a ZIM path is never
encoded, so the `#` is part of the path. It is then re-encoded to `%23`
by the existing quote() call, which matches what the JS side
(wombatSetup.js) already produces via encodeURIComponent().

Fix #341
---
 CHANGELOG.md                                 |  1 +
 src/zimscraperlib/rewriting/url_rewriting.py |  4 ++-
 tests/rewriting/test_url_rewriting.py        | 33 ++++++++++++++++++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a29db71..d40b54f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Carry a script's top-level `const`, `let` and `class` declarations across the wombat block, so other scripts on the page can still see them (#329)
 - Keep a rewritten `<script>`'s original `src` in `__wb_orig_src`, so wombat can return it from `getAttribute("src")` and bundlers that identify chunks by it (Next.js/Turbopack, Vite) still work (openzim/warc2zim#473)
+- Keep URL-encoded `#` characters of the path or querystring when rewriting document URIs, instead of dropping everything after them (#341)
 
 ## [5.4.1] - 2026-07-31
 
diff --git a/src/zimscraperlib/rewriting/url_rewriting.py b/src/zimscraperlib/rewriting/url_rewriting.py
index fffe5e0..69822fa 100644
--- a/src/zimscraperlib/rewriting/url_rewriting.py
+++ b/src/zimscraperlib/rewriting/url_rewriting.py
@@ -312,7 +312,9 @@ def get_document_uri(self, item_path: ZimPath, item_fragment: str) -> str:
         URI.
 
         """
-        item_parts = urlsplit(item_path.value)
+        # a ZIM path is never URL-encoded, so a `#` in it is a literal character
+        # (e.g. coming from a `%23` in original URL) and not a fragment delimiter
+        item_parts = urlsplit(item_path.value, allow_fragments=False)
 
         # item_path is both path + querystring, both will be url-encoded in the document
         # so that readers consider them as a whole and properly pass them to libzim
diff --git a/tests/rewriting/test_url_rewriting.py b/tests/rewriting/test_url_rewriting.py
index 7f5d494..2469084 100644
--- a/tests/rewriting/test_url_rewriting.py
+++ b/tests/rewriting/test_url_rewriting.py
@@ -206,6 +206,39 @@ def test_missing_zim_paths(
                 ["kiwix.org/a/article/foo.html?foo=b?ar"],
                 False,
             ),
+            (
+                "https://kiwix.org/a/article/document.html",
+                "foo%23bar.html",  # a path with an encoded # char
+                RewriteResult(
+                    "https://kiwix.org/a/article/foo%23bar.html",
+                    "foo%23bar.html",
+                    ZimPath("kiwix.org/a/article/foo#bar.html"),
+                ),
+                ["kiwix.org/a/article/foo#bar.html"],
+                False,
+            ),
+            (
+                "https://kiwix.org/a/article/document.html",
+                "foo%23bar.html#anchor1",  # encoded # char followed by a fragment
+                RewriteResult(
+                    "https://kiwix.org/a/article/foo%23bar.html#anchor1",
+                    "foo%23bar.html#anchor1",
+                    ZimPath("kiwix.org/a/article/foo#bar.html"),
+                ),
+                ["kiwix.org/a/article/foo#bar.html"],
+                False,
+            ),
+            (
+                "https://kiwix.org/a/article/document.html",
+                "foo.html?foo=b%23ar",  # a query string with an encoded # char
+                RewriteResult(
+                    "https://kiwix.org/a/article/foo.html?foo=b%23ar",
+                    "foo.html%3Ffoo=b%23ar",
+                    ZimPath("kiwix.org/a/article/foo.html?foo=b#ar"),
+                ),
+                ["kiwix.org/a/article/foo.html?foo=b#ar"],
+                False,
+            ),
             (
                 "https://kiwix.org/a/article/document.html",
                 "fo%o.html",