From 86197cebe168fa59dd7c5ebc1b2fe9ae9dec038e Mon Sep 17 00:00:00 2001
From: Martijn Pieters <mj@zopatista.com>
Date: Wed, 19 Apr 2023 16:18:00 +0100
Subject: [PATCH] update_query({}) should be a no-op.

---
 CHANGES/845.bugfix.rst |  2 ++
 yarl/_url.py           | 10 ++++++----
 2 files changed, 8 insertions(+), 4 deletions(-)
 create mode 100644 CHANGES/845.bugfix.rst

diff --git a/CHANGES/845.bugfix.rst b/CHANGES/845.bugfix.rst
new file mode 100644
index 000000000..fbc7a70af
--- /dev/null
+++ b/CHANGES/845.bugfix.rst
@@ -0,0 +1,2 @@
+Fixed an issue with ``update_query()`` getting rid of the query when the argument
+is empty but not ``None``.
diff --git a/yarl/_url.py b/yarl/_url.py
index e21c5e96e..3ddb1fa8f 100644
--- a/yarl/_url.py
+++ b/yarl/_url.py
@@ -956,7 +956,7 @@ def _get_str_query(self, *args, **kwargs):
             raise ValueError("Either kwargs or single query parameter must be present")
 
         if query is None:
-            query = ""
+            query = None
         elif isinstance(query, Mapping):
             quoter = self._QUERY_PART_QUOTER
             query = "&".join(self._query_seq_pairs(quoter, query.items()))
@@ -998,7 +998,7 @@ def with_query(self, *args, **kwargs):
         """
         # N.B. doesn't cleanup query/fragment
 
-        new_query = self._get_str_query(*args, **kwargs)
+        new_query = self._get_str_query(*args, **kwargs) or ""
         return URL(
             self._val._replace(path=self._val.path, query=new_query), encoded=True
         )
@@ -1007,12 +1007,14 @@ def update_query(self, *args, **kwargs):
         """Return a new URL with query part updated."""
         s = self._get_str_query(*args, **kwargs)
         query = None
-        if s:
+        if s is not None:
             new_query = MultiDict(parse_qsl(s, keep_blank_values=True))
             query = MultiDict(self.query)
             query.update(new_query)
 
-        return URL(self._val._replace(query=self._get_str_query(query)), encoded=True)
+        return URL(
+            self._val._replace(query=self._get_str_query(query) or ""), encoded=True
+        )
 
     def with_fragment(self, fragment):
         """Return a new URL with fragment replaced.