fix: empty list is not an empty value for list filters even when a custom filtering method is provided (#1450)

Co-authored-by: Thomas Leonard <thomas@loftorbital.com>

graphene_django/compat.py

@@ -1,3 +1,6 @@
+import sys
+from pathlib import PurePath
+
 # For backwards compatibility, we import JSONField to have it available for import via
 # this compat module (https://github.com/graphql-python/graphene-django/issues/1428).
 # Django's JSONField is available in Django 3.2+ (the minimum version we support)
@@ -19,4 +22,23 @@ try:
         RangeField,
     )
 except ImportError:
-    IntegerRangeField, ArrayField, HStoreField, RangeField = (MissingType,) * 4
+    IntegerRangeField, HStoreField, RangeField = (MissingType,) * 3
+
+    # For unit tests we fake ArrayField using JSONFields
+    if any(
+        PurePath(sys.argv[0]).match(p)
+        for p in [
+            "**/pytest",
+            "**/py.test",
+            "**/pytest/__main__.py",
+        ]
+    ):
+
+        class ArrayField(JSONField):
+            def __init__(self, *args, **kwargs):
+                if len(args) > 0:
+                    self.base_field = args[0]
+                super().__init__(**kwargs)
+
+    else:
+        ArrayField = MissingType

graphene_django/filter/filters/array_filter.py

@@ -1,13 +1,36 @@
 from django_filters.constants import EMPTY_VALUES
+from django_filters.filters import FilterMethod
 
 from .typed_filter import TypedFilter
 
 
+class ArrayFilterMethod(FilterMethod):
+    def __call__(self, qs, value):
+        if value is None:
+            return qs
+        return self.method(qs, self.f.field_name, value)
+
+
 class ArrayFilter(TypedFilter):
     """
     Filter made for PostgreSQL ArrayField.
     """
 
+    @TypedFilter.method.setter
+    def method(self, value):
+        """
+        Override method setter so that in case a custom `method` is provided
+        (see documentation https://django-filter.readthedocs.io/en/stable/ref/filters.html#method),
+        it doesn't fall back to checking if the value is in `EMPTY_VALUES` (from the `__call__` method
+        of the `FilterMethod` class) and instead use our ArrayFilterMethod that consider empty lists as values.
+
+        Indeed when providing a `method` the `filter` method below is overridden and replaced by `FilterMethod(self)`
+        which means that the validation of the empty value is made by the `FilterMethod.__call__` method instead.
+        """
+        TypedFilter.method.fset(self, value)
+        if value is not None:
+            self.filter = ArrayFilterMethod(self)
+
     def filter(self, qs, value):
         """
         Override the default filter class to check first whether the list is

graphene_django/filter/filters/list_filter.py

@@ -1,12 +1,36 @@
+from django_filters.filters import FilterMethod
+
 from .typed_filter import TypedFilter
 
 
+class ListFilterMethod(FilterMethod):
+    def __call__(self, qs, value):
+        if value is None:
+            return qs
+        return self.method(qs, self.f.field_name, value)
+
+
 class ListFilter(TypedFilter):
     """
     Filter that takes a list of value as input.
     It is for example used for `__in` filters.
     """
 
+    @TypedFilter.method.setter
+    def method(self, value):
+        """
+        Override method setter so that in case a custom `method` is provided
+        (see documentation https://django-filter.readthedocs.io/en/stable/ref/filters.html#method),
+        it doesn't fall back to checking if the value is in `EMPTY_VALUES` (from the `__call__` method
+        of the `FilterMethod` class) and instead use our ListFilterMethod that consider empty lists as values.
+
+        Indeed when providing a `method` the `filter` method below is overridden and replaced by `FilterMethod(self)`
+        which means that the validation of the empty value is made by the `FilterMethod.__call__` method instead.
+        """
+        TypedFilter.method.fset(self, value)
+        if value is not None:
+            self.filter = ListFilterMethod(self)
+
     def filter(self, qs, value):
         """
         Override the default filter class to check first whether the list is

graphene_django/filter/tests/conftest.py

@@ -1,4 +1,4 @@
-from unittest.mock import MagicMock
+from functools import reduce
 
 import pytest
 from django.db import models
@@ -25,15 +25,15 @@ else:
     )
 
 
-STORE = {"events": []}
-
-
 class Event(models.Model):
     name = models.CharField(max_length=50)
     tags = ArrayField(models.CharField(max_length=50))
     tag_ids = ArrayField(models.IntegerField())
     random_field = ArrayField(models.BooleanField())
 
+    def __repr__(self):
+        return f"Event [{self.name}]"
+
 
 @pytest.fixture
 def EventFilterSet():
@@ -48,6 +48,14 @@ def EventFilterSet():
         tags__contains = ArrayFilter(field_name="tags", lookup_expr="contains")
         tags__overlap = ArrayFilter(field_name="tags", lookup_expr="overlap")
         tags = ArrayFilter(field_name="tags", lookup_expr="exact")
+        tags__len = ArrayFilter(
+            field_name="tags", lookup_expr="len", input_type=graphene.Int
+        )
+        tags__len__in = ArrayFilter(
+            field_name="tags",
+            method="tags__len__in_filter",
+            input_type=graphene.List(graphene.Int),
+        )
 
         # Those are actually not usable and only to check type declarations
         tags_ids__contains = ArrayFilter(field_name="tag_ids", lookup_expr="contains")
@@ -61,6 +69,14 @@ def EventFilterSet():
         )
         random_field = ArrayFilter(field_name="random_field", lookup_expr="exact")
 
+        def tags__len__in_filter(self, queryset, _name, value):
+            if not value:
+                return queryset.none()
+            return reduce(
+                lambda q1, q2: q1.union(q2),
+                [queryset.filter(tags__len=v) for v in value],
+            ).distinct()
+
     return EventFilterSet
 
 
@@ -83,68 +99,94 @@ def Query(EventType):
     we are running unit tests in sqlite which does not have ArrayFields.
     """
 
+    events = [
+        Event(name="Live Show", tags=["concert", "music", "rock"]),
+        Event(name="Musical", tags=["movie", "music"]),
+        Event(name="Ballet", tags=["concert", "dance"]),
+        Event(name="Speech", tags=[]),
+    ]
+
     class Query(graphene.ObjectType):
         events = DjangoFilterConnectionField(EventType)
 
         def resolve_events(self, info, **kwargs):
-            events = [
+            class FakeQuerySet(QuerySet):
-                Event(name="Live Show", tags=["concert", "music", "rock"]),
+                def __init__(self, model=None):
-                Event(name="Musical", tags=["movie", "music"]),
+                    self.model = Event
-                Event(name="Ballet", tags=["concert", "dance"]),
+                    self.__store = list(events)
-                Event(name="Speech", tags=[]),
-            ]
 
-            STORE["events"] = events
+                def all(self):
+                    return self
 
-            m_queryset = MagicMock(spec=QuerySet)
+                def filter(self, **kwargs):
-            m_queryset.model = Event
+                    queryset = FakeQuerySet()
-
+                    queryset.__store = list(self.__store)
-            def filter_events(**kwargs):
+                    if "tags__contains" in kwargs:
-                if "tags__contains" in kwargs:
+                        queryset.__store = list(
-                    STORE["events"] = list(
+                            filter(
-                        filter(
+                                lambda e: set(kwargs["tags__contains"]).issubset(
-                            lambda e: set(kwargs["tags__contains"]).issubset(
+                                    set(e.tags)
-                                set(e.tags)
+                                ),
-                            ),
+                                queryset.__store,
-                            STORE["events"],
+                            )
                         )
-                    )
+                    if "tags__overlap" in kwargs:
-                if "tags__overlap" in kwargs:
+                        queryset.__store = list(
-                    STORE["events"] = list(
+                            filter(
-                        filter(
+                                lambda e: not set(kwargs["tags__overlap"]).isdisjoint(
-                            lambda e: not set(kwargs["tags__overlap"]).isdisjoint(
+                                    set(e.tags)
-                                set(e.tags)
+                                ),
-                            ),
+                                queryset.__store,
-                            STORE["events"],
+                            )
                         )
-                    )
+                    if "tags__exact" in kwargs:
-                if "tags__exact" in kwargs:
+                        queryset.__store = list(
-                    STORE["events"] = list(
+                            filter(
-                        filter(
+                                lambda e: set(kwargs["tags__exact"]) == set(e.tags),
-                            lambda e: set(kwargs["tags__exact"]) == set(e.tags),
+                                queryset.__store,
-                            STORE["events"],
+                            )
                         )
-                    )
+                    if "tags__len" in kwargs:
+                        queryset.__store = list(
+                            filter(
+                                lambda e: len(e.tags) == kwargs["tags__len"],
+                                queryset.__store,
+                            )
+                        )
+                    return queryset
 
-            def mock_queryset_filter(*args, **kwargs):
+                def union(self, *args):
-                filter_events(**kwargs)
+                    queryset = FakeQuerySet()
-                return m_queryset
+                    queryset.__store = self.__store
+                    for arg in args:
+                        queryset.__store += arg.__store
+                    return queryset
 
-            def mock_queryset_none(*args, **kwargs):
+                def none(self):
-                STORE["events"] = []
+                    queryset = FakeQuerySet()
-                return m_queryset
+                    queryset.__store = []
+                    return queryset
 
-            def mock_queryset_count(*args, **kwargs):
+                def count(self):
-                return len(STORE["events"])
+                    return len(self.__store)
 
-            m_queryset.all.return_value = m_queryset
+                def distinct(self):
-            m_queryset.filter.side_effect = mock_queryset_filter
+                    queryset = FakeQuerySet()
-            m_queryset.none.side_effect = mock_queryset_none
+                    queryset.__store = []
-            m_queryset.count.side_effect = mock_queryset_count
+                    for event in self.__store:
-            m_queryset.__getitem__.side_effect = lambda index: STORE[
+                        if event not in queryset.__store:
-                "events"
+                            queryset.__store.append(event)
-            ].__getitem__(index)
+                    queryset.__store = sorted(queryset.__store, key=lambda e: e.name)
+                    return queryset
 
-            return m_queryset
+                def __getitem__(self, index):
+                    return self.__store[index]
+
+            return FakeQuerySet()
 
     return Query
+
+
+@pytest.fixture
+def schema(Query):
+    return graphene.Schema(query=Query)

graphene_django/filter/tests/test_array_field_contains_filter.py

@@ -1,18 +1,14 @@
 import pytest
 
-from graphene import Schema
-
 from ...compat import ArrayField, MissingType
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_contains_multiple(Query):
+def test_array_field_contains_multiple(schema):
     """
     Test contains filter on a array field of string.
     """
 
-    schema = Schema(query=Query)
-
     query = """
     query {
         events (tags_Contains: ["concert", "music"]) {
@@ -32,13 +28,11 @@ def test_array_field_contains_multiple(Query):
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_contains_one(Query):
+def test_array_field_contains_one(schema):
     """
     Test contains filter on a array field of string.
     """
 
-    schema = Schema(query=Query)
-
     query = """
     query {
         events (tags_Contains: ["music"]) {
@@ -59,13 +53,11 @@ def test_array_field_contains_one(Query):
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_contains_empty_list(Query):
+def test_array_field_contains_empty_list(schema):
     """
     Test contains filter on a array field of string.
     """
 
-    schema = Schema(query=Query)
-
     query = """
     query {
         events (tags_Contains: []) {

graphene_django/filter/tests/test_array_field_custom_filter.py

@@ -0,0 +1,186 @@
+import pytest
+
+from ...compat import ArrayField, MissingType
+
+
+@pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
+def test_array_field_len_filter(schema):
+    query = """
+    query {
+        events (tags_Len: 2) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["events"]["edges"] == [
+        {"node": {"name": "Musical"}},
+        {"node": {"name": "Ballet"}},
+    ]
+
+    query = """
+    query {
+        events (tags_Len: 0) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["events"]["edges"] == [
+        {"node": {"name": "Speech"}},
+    ]
+
+    query = """
+    query {
+        events (tags_Len: 10) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["events"]["edges"] == []
+
+    query = """
+    query {
+        events (tags_Len: "2") {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert len(result.errors) == 1
+    assert result.errors[0].message == 'Int cannot represent non-integer value: "2"'
+
+    query = """
+    query {
+        events (tags_Len: True) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert len(result.errors) == 1
+    assert result.errors[0].message == "Int cannot represent non-integer value: True"
+
+
+@pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
+def test_array_field_custom_filter(schema):
+    query = """
+    query {
+        events (tags_Len_In: 2) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["events"]["edges"] == [
+        {"node": {"name": "Ballet"}},
+        {"node": {"name": "Musical"}},
+    ]
+
+    query = """
+    query {
+        events (tags_Len_In: [0, 2]) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["events"]["edges"] == [
+        {"node": {"name": "Ballet"}},
+        {"node": {"name": "Musical"}},
+        {"node": {"name": "Speech"}},
+    ]
+
+    query = """
+    query {
+        events (tags_Len_In: [10]) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["events"]["edges"] == []
+
+    query = """
+    query {
+        events (tags_Len_In: []) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["events"]["edges"] == []
+
+    query = """
+    query {
+        events (tags_Len_In: "12") {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert len(result.errors) == 1
+    assert result.errors[0].message == 'Int cannot represent non-integer value: "12"'
+
+    query = """
+    query {
+        events (tags_Len_In: True) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert len(result.errors) == 1
+    assert result.errors[0].message == "Int cannot represent non-integer value: True"

graphene_django/filter/tests/test_array_field_exact_filter.py

@@ -1,18 +1,14 @@
 import pytest
 
-from graphene import Schema
-
 from ...compat import ArrayField, MissingType
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_exact_no_match(Query):
+def test_array_field_exact_no_match(schema):
     """
     Test exact filter on a array field of string.
     """
 
-    schema = Schema(query=Query)
-
     query = """
     query {
         events (tags: ["concert", "music"]) {
@@ -30,13 +26,11 @@ def test_array_field_exact_no_match(Query):
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_exact_match(Query):
+def test_array_field_exact_match(schema):
     """
     Test exact filter on a array field of string.
     """
 
-    schema = Schema(query=Query)
-
     query = """
     query {
         events (tags: ["movie", "music"]) {
@@ -56,13 +50,11 @@ def test_array_field_exact_match(Query):
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_exact_empty_list(Query):
+def test_array_field_exact_empty_list(schema):
     """
     Test exact filter on a array field of string.
     """
 
-    schema = Schema(query=Query)
-
     query = """
     query {
         events (tags: []) {
@@ -82,11 +74,10 @@ def test_array_field_exact_empty_list(Query):
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_filter_schema_type(Query):
+def test_array_field_filter_schema_type(schema):
     """
     Check that the type in the filter is an array field like on the object type.
     """
-    schema = Schema(query=Query)
     schema_str = str(schema)
 
     assert (
@@ -112,6 +103,8 @@ def test_array_field_filter_schema_type(Query):
         "tags_Contains": "[String!]",
         "tags_Overlap": "[String!]",
         "tags": "[String!]",
+        "tags_Len": "Int",
+        "tags_Len_In": "[Int]",
         "tagsIds_Contains": "[Int!]",
         "tagsIds_Overlap": "[Int!]",
         "tagsIds": "[Int!]",

graphene_django/filter/tests/test_array_field_overlap_filter.py

@@ -1,18 +1,14 @@
 import pytest
 
-from graphene import Schema
-
 from ...compat import ArrayField, MissingType
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_overlap_multiple(Query):
+def test_array_field_overlap_multiple(schema):
     """
     Test overlap filter on a array field of string.
     """
 
-    schema = Schema(query=Query)
-
     query = """
     query {
         events (tags_Overlap: ["concert", "music"]) {
@@ -34,13 +30,11 @@ def test_array_field_overlap_multiple(Query):
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_overlap_one(Query):
+def test_array_field_overlap_one(schema):
     """
     Test overlap filter on a array field of string.
     """
 
-    schema = Schema(query=Query)
-
     query = """
     query {
         events (tags_Overlap: ["music"]) {
@@ -61,13 +55,11 @@ def test_array_field_overlap_one(Query):
 
 
 @pytest.mark.skipif(ArrayField is MissingType, reason="ArrayField should exist")
-def test_array_field_overlap_empty_list(Query):
+def test_array_field_overlap_empty_list(schema):
     """
     Test overlap filter on a array field of string.
     """
 
-    schema = Schema(query=Query)
-
     query = """
     query {
         events (tags_Overlap: []) {

graphene_django/filter/tests/test_typed_filter.py

@@ -1,4 +1,8 @@
+import operator
+from functools import reduce
+
 import pytest
+from django.db.models import Q
 from django_filters import FilterSet
 
 import graphene
@@ -44,6 +48,10 @@ def schema():
         only_first = TypedFilter(
             input_type=graphene.Boolean, method="only_first_filter"
         )
+        headline_search = ListFilter(
+            method="headline_search_filter",
+            input_type=graphene.List(graphene.String),
+        )
 
         def first_n_filter(self, queryset, _name, value):
             return queryset[:value]
@@ -54,6 +62,13 @@ def schema():
             else:
                 return queryset
 
+        def headline_search_filter(self, queryset, _name, value):
+            if not value:
+                return queryset.none()
+            return queryset.filter(
+                reduce(operator.or_, [Q(headline__icontains=v) for v in value])
+            )
+
     class ArticleType(DjangoObjectType):
         class Meta:
             model = Article
@@ -87,6 +102,7 @@ def test_typed_filter_schema(schema):
         "lang_InStr": "[String]",
         "firstN": "Int",
         "onlyFirst": "Boolean",
+        "headlineSearch": "[String]",
     }
 
     all_articles_filters = (
@@ -104,24 +120,7 @@ def test_typed_filters_work(schema):
     Article.objects.create(headline="A", reporter=reporter, editor=reporter, lang="es")
     Article.objects.create(headline="B", reporter=reporter, editor=reporter, lang="es")
     Article.objects.create(headline="C", reporter=reporter, editor=reporter, lang="en")
-
+    Article.objects.create(headline="AB", reporter=reporter, editor=reporter, lang="es")
-    query = "query { articles (lang_In: [ES]) { edges { node { headline } } } }"
-
-    result = schema.execute(query)
-    assert not result.errors
-    assert result.data["articles"]["edges"] == [
-        {"node": {"headline": "A"}},
-        {"node": {"headline": "B"}},
-    ]
-
-    query = 'query { articles (lang_InStr: ["es"]) { edges { node { headline } } } }'
-
-    result = schema.execute(query)
-    assert not result.errors
-    assert result.data["articles"]["edges"] == [
-        {"node": {"headline": "A"}},
-        {"node": {"headline": "B"}},
-    ]
 
     query = 'query { articles (lang_Contains: "n") { edges { node { headline } } } }'
 
@@ -137,7 +136,7 @@ def test_typed_filters_work(schema):
     assert not result.errors
     assert result.data["articles"]["edges"] == [
         {"node": {"headline": "A"}},
-        {"node": {"headline": "B"}},
+        {"node": {"headline": "AB"}},
     ]
 
     query = "query { articles (onlyFirst: true) { edges { node { headline } } } }"
@@ -147,3 +146,86 @@ def test_typed_filters_work(schema):
     assert result.data["articles"]["edges"] == [
         {"node": {"headline": "A"}},
     ]
+
+
+def test_list_filters_work(schema):
+    reporter = Reporter.objects.create(first_name="John", last_name="Doe", email="")
+    Article.objects.create(headline="A", reporter=reporter, editor=reporter, lang="es")
+    Article.objects.create(headline="B", reporter=reporter, editor=reporter, lang="es")
+    Article.objects.create(headline="C", reporter=reporter, editor=reporter, lang="en")
+    Article.objects.create(headline="AB", reporter=reporter, editor=reporter, lang="es")
+
+    query = "query { articles (lang_In: [ES]) { edges { node { headline } } } }"
+
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["articles"]["edges"] == [
+        {"node": {"headline": "A"}},
+        {"node": {"headline": "AB"}},
+        {"node": {"headline": "B"}},
+    ]
+
+    query = 'query { articles (lang_InStr: ["es"]) { edges { node { headline } } } }'
+
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["articles"]["edges"] == [
+        {"node": {"headline": "A"}},
+        {"node": {"headline": "AB"}},
+        {"node": {"headline": "B"}},
+    ]
+
+    query = "query { articles (lang_InStr: []) { edges { node { headline } } } }"
+
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["articles"]["edges"] == []
+
+    query = "query { articles (lang_InStr: null) { edges { node { headline } } } }"
+
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["articles"]["edges"] == [
+        {"node": {"headline": "A"}},
+        {"node": {"headline": "AB"}},
+        {"node": {"headline": "B"}},
+        {"node": {"headline": "C"}},
+    ]
+
+    query = 'query { articles (headlineSearch: ["a", "B"]) { edges { node { headline } } } }'
+
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["articles"]["edges"] == [
+        {"node": {"headline": "A"}},
+        {"node": {"headline": "AB"}},
+        {"node": {"headline": "B"}},
+    ]
+
+    query = "query { articles (headlineSearch: []) { edges { node { headline } } } }"
+
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["articles"]["edges"] == []
+
+    query = "query { articles (headlineSearch: null) { edges { node { headline } } } }"
+
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["articles"]["edges"] == [
+        {"node": {"headline": "A"}},
+        {"node": {"headline": "AB"}},
+        {"node": {"headline": "B"}},
+        {"node": {"headline": "C"}},
+    ]
+
+    query = 'query { articles (headlineSearch: [""]) { edges { node { headline } } } }'
+
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["articles"]["edges"] == [
+        {"node": {"headline": "A"}},
+        {"node": {"headline": "AB"}},
+        {"node": {"headline": "B"}},
+        {"node": {"headline": "C"}},
+    ]