Issue 1195 (#1196)

Closes #1195

Author: asvetlov

CHANGES/1195.bugfix.rst

@@ -0,0 +1,6 @@
+Fix a bug in C implementation when during multidict resizing the function could drop
+last item under some circumstances.
+
+The bug was introduced by multidict 6.5.0 release.
+
+Patch by :user:`asvetlov`.

multidict/_multilib/hashtable.h

@@ -207,12 +207,12 @@ _md_resize(MultiDictObject *md, uint8_t log2_newsize, bool update)
     if (oldkeys->nentries == numentries) {
         memcpy(newentries, oldentries, numentries * sizeof(entry_t));
     } else {
-        entry_t *ep = oldentries;
-        for (Py_ssize_t i = 0; i < numentries; i++) {
-            if (!update) {
-                while (ep->identity == NULL) ep++;
+        entry_t *new_ep = newentries;
+        entry_t *old_ep = oldentries;
+        for (Py_ssize_t i = 0; i < oldkeys->nentries; ++i, ++old_ep) {
+            if (old_ep->identity != NULL) {
+                *new_ep++ = *old_ep;
             }
-            newentries[i] = *ep++;
         }
     }
 

tests/test_mutable_multidict.py

@@ -793,3 +793,23 @@ def test_keys_type(
 
         k, v = d.popitem()
         assert type(k) is case_insensitive_str_class
+
+    def test_issue_1195(
+        self, case_insensitive_multidict_class: type[CIMultiDict[bytes]]
+    ) -> None:
+        md = case_insensitive_multidict_class(
+            {
+                "User-Agent": b"Bacon/1.0",
+                "Cookie": b"valued-visitor=yes;foo=bar",
+                "X-Bar": b"Foo",
+                "X-Foo": b"Bar",
+                "Referer": b"https://httpie.org/",
+            }
+        )
+
+        md2 = md.copy()
+
+        md.popone("User-Agent")
+        assert md.keys() == md2.keys() - {"User-Agent"}
+        md.update([("User-Agent", b"Bacon/1.0")])
+        assert md.keys() == md2.keys()