validate plurals in suggestion API

Author: gersona

weblate/api/serializers.py

@@ -2293,6 +2293,16 @@ class Meta:
         model = Suggestion
         fields = ("id", "unit", "target", "user", "timestamp", "votes")
 
+    def validate_target(self, value: list[str]) -> list[str]:
+        unit = self.context.get("unit")
+        if unit is None:
+            return value
+        target_copy = value.copy()
+        if target_copy != unit.adjust_plurals(value.copy()):
+            msg = gettext_lazy("Number of plurals does not match")
+            raise serializers.ValidationError(msg)
+        return value
+
     def create(self, validated_data):
         request = self.context["request"]
         unit = self.context["unit"]

weblate/api/tests.py

@@ -11086,7 +11086,20 @@ def test_add_suggestion_plural(self) -> None:
         unit = Unit.objects.get(
             translation__language_code="cs", source__startswith="Orangutan has "
         )
-        target = ["Orangutan má %d banán.\n", "Orangutan má %d banány.\n"]
+        target = [
+            "Orangutan má %d banán.\n",
+            "Orangutan má %d banány.\n",
+        ]
+        response = self._add_suggestion(unit, target, code=400)
+        self.assertEqual(
+            response.data["errors"][0]["detail"],
+            "Number of plurals does not match",
+        )
+        target = [
+            "Orangutan má %d banán.\n",
+            "Orangutan má %d banány.\n",
+            "Orangutan má %d banánů.\n",
+        ]
         response = self._add_suggestion(unit, target)
         self.assertEqual(response.data["target"], target)