Fix sort_by on embedded model field paths

aredis_om/model/model.py

@@ -1427,17 +1427,42 @@ def query_params(self):
             params += [attr for kv in self.knn.query_params.items() for attr in kv]
         return params
 
+    def _resolve_sort_field(self, field_name: str):
+        """
+        Resolve a sort field name to its field proxy and RediSearch field name.
+
+        Embedded model fields can be given as 'parent__child' or 'parent.child'.
+        """
+        parts = field_name.replace("__", ".").split(".")
+        if len(parts) == 1:
+            if field_name not in self.model.model_fields:  # type: ignore
+                return None
+            return getattr(self.model, field_name), field_name
+
+        try:
+            field_proxy = getattr(self.model, parts[0])
+            for part in parts[1:]:
+                field_proxy = getattr(field_proxy, part)
+        except (AttributeError, QuerySyntaxError):
+            return None
+        if not isinstance(field_proxy, ExpressionProxy):
+            return None
+        # Embedded fields are indexed as "<parent>_<child>", as in find().
+        prefix = "_".join(parent[0] for parent in field_proxy.parents)
+        return field_proxy, f"{prefix}_{field_proxy.field.name}"
+
     def validate_sort_fields(self, sort_fields: List[str]):
         for sort_field in sort_fields:
             field_name = sort_field.lstrip("-")
             if self.knn and field_name == self.knn.score_field_name:
                 continue
-            if field_name not in self.model.model_fields:  # type: ignore
+            resolved = self._resolve_sort_field(field_name)
+            if resolved is None:
                 raise QueryNotSupportedError(
                     f"You tried sort by {field_name}, but that field "
                     f"does not exist on the model {self.model}"
                 )
-            field_proxy: ExpressionProxy = getattr(self.model, field_name)
+            field_proxy: ExpressionProxy = resolved[0]
 
             if (
                 field_proxy.field.sortable is not True
@@ -1710,7 +1735,12 @@ def resolve_redisearch_sort_fields(self):
         fields = []
         for f in self.sort_fields:
             direction = "desc" if f.startswith("-") else "asc"
-            fields.extend([f.lstrip("-"), direction])
+            field_name = f.lstrip("-")
+            if self.knn and field_name == self.knn.score_field_name:
+                resolved_name = field_name
+            else:
+                resolved_name = self._resolve_sort_field(field_name)[1]  # type: ignore
+            fields.extend([resolved_name, direction])
         if self.sort_fields:
             return ["SORTBY", *fields]
 

tests/test_json_model.py

@@ -756,6 +756,46 @@ async def test_sorting(members, m):
         await m.Member.find().sort_by("join_date").all()
 
 
+@py_test_mark_asyncio
+async def test_sorting_on_embedded_field(key_prefix, redis):
+    class Metrics(EmbeddedJsonModel, index=True):
+        score: int = Field(index=True, sortable=True)
+        label: str = Field(index=True)
+        unindexed: int = 0
+
+    class Book(JsonModel, index=True):
+        title: str = Field(index=True)
+        metrics: Metrics
+
+        class Meta:
+            global_key_prefix = key_prefix
+            database = redis
+
+    await Migrator(conn=redis).run()
+
+    low = await Book(title="Low", metrics=Metrics(score=1, label="a")).save()
+    mid = await Book(title="Mid", metrics=Metrics(score=2, label="b")).save()
+    high = await Book(title="High", metrics=Metrics(score=5, label="c")).save()
+
+    for path in ("metrics__score", "metrics.score"):
+        actual = await Book.find(Book.metrics.score < 10).sort_by(path).all()
+        assert actual == [low, mid, high]
+
+        actual = await Book.find(Book.metrics.score < 10).sort_by(f"-{path}").all()
+        assert actual == [high, mid, low]
+
+    query = Book.find().sort_by("metrics.score")
+    assert query.resolve_redisearch_sort_fields() == ["SORTBY", "metrics_score", "asc"]
+
+    with pytest.raises(QueryNotSupportedError):
+        # This embedded field does not exist.
+        Book.find().sort_by("metrics.nope")
+
+    with pytest.raises(QueryNotSupportedError):
+        # This embedded field is not sortable or indexed.
+        Book.find().sort_by("metrics.unindexed")
+
+
 @py_test_mark_asyncio
 async def test_case_sensitive(members, m):
     member1, member2, member3 = members