Fix hasPreviousPage

This commit implements a fix for
graphql-python/graphql-relay-py#12

The project `graphql-relay-py` seems unmaintained, so there is
little hope that
[this PR](graphql-python/graphql-relay-py#14)
gets merged any time soon.

Closes projectcaluma#469

Author: open-dynaMIX

caluma/core/filters.py

@@ -36,6 +36,7 @@
 
 from .forms import GlobalIDFormField, GlobalIDMultipleChoiceField
 from .relay import extract_global_id
+from .types import DjangoConnectionField
 
 
 class GlobalIDFilter(Filter):
@@ -414,7 +415,9 @@ class MetaFilterSet(FilterSet):
     meta_value = MetaValueFilter(field_name="meta")
 
 
-class DjangoFilterConnectionField(filter.DjangoFilterConnectionField):
+class DjangoFilterConnectionField(
+    filter.DjangoFilterConnectionField, DjangoConnectionField
+):
     """
     Django connection filter field with object type get_queryset support.
 

caluma/core/pagination.py

@@ -0,0 +1,94 @@
+from graphql_relay.connection.arrayconnection import (
+    get_offset_with_default,
+    offset_to_cursor,
+)
+from graphql_relay.connection.connectiontypes import Connection, Edge, PageInfo
+
+
+def connection_from_list(data, args=None, **kwargs):
+    """
+    Replace graphql_relay.connection.arrayconnection.connection_from_list.
+
+    This can be removed, when (or better if)
+    https://github.com/graphql-python/graphql-relay-py/issues/12
+    is resolved.
+
+    A simple function that accepts an array and connection arguments, and returns
+    a connection object for use in GraphQL. It uses array offsets as pagination,
+    so pagination will only work if the array is static.
+    """
+    _len = len(data)
+    return connection_from_list_slice(
+        data, args, slice_start=0, list_length=_len, list_slice_length=_len, **kwargs
+    )
+
+
+def connection_from_list_slice(
+    list_slice,
+    args=None,
+    connection_type=None,
+    edge_type=None,
+    pageinfo_type=None,
+    slice_start=0,
+    list_length=0,
+    list_slice_length=None,
+):
+    """
+    Replace graphql_relay.connection.arrayconnection.connection_from_list_slice.
+
+    This can be removed, when (or better if)
+    https://github.com/graphql-python/graphql-relay-py/issues/12
+    is resolved.
+
+    Given a slice (subset) of an array, returns a connection object for use in
+    GraphQL.
+    This function is similar to `connectionFromArray`, but is intended for use
+    cases where you know the cardinality of the connection, consider it too large
+    to materialize the entire array, and instead wish pass in a slice of the
+    total result large enough to cover the range specified in `args`.
+    """
+    connection_type = connection_type or Connection
+    edge_type = edge_type or Edge
+    pageinfo_type = pageinfo_type or PageInfo
+
+    args = args or {}
+
+    before = args.get("before")
+    after = args.get("after")
+    first = args.get("first")
+    last = args.get("last")
+    if list_slice_length is None:  # pragma: no cover
+        list_slice_length = len(list_slice)
+    slice_end = slice_start + list_slice_length
+    before_offset = get_offset_with_default(before, list_length)
+    after_offset = get_offset_with_default(after, -1)
+
+    start_offset = max(slice_start - 1, after_offset, -1) + 1
+    end_offset = min(slice_end, before_offset, list_length)
+    if isinstance(first, int):
+        end_offset = min(end_offset, start_offset + first)
+    if isinstance(last, int):
+        start_offset = max(start_offset, end_offset - last)
+
+    # If supplied slice is too large, trim it down before mapping over it.
+    _slice = list_slice[
+        max(start_offset - slice_start, 0) : list_slice_length
+        - (slice_end - end_offset)
+    ]
+    edges = [
+        edge_type(node=node, cursor=offset_to_cursor(start_offset + i))
+        for i, node in enumerate(_slice)
+    ]
+
+    first_edge_cursor = edges[0].cursor if edges else None
+    last_edge_cursor = edges[-1].cursor if edges else None
+
+    return connection_type(
+        edges=edges,
+        page_info=pageinfo_type(
+            start_cursor=first_edge_cursor,
+            end_cursor=last_edge_cursor,
+            has_previous_page=start_offset > 0,
+            has_next_page=end_offset < list_length,
+        ),
+    )

caluma/core/tests/test_pagination.py

@@ -1,3 +1,6 @@
+import pytest
+
+
 def test_offset_pagination(db, schema_executor, document_factory):
     document_factory(meta={"position": 0})
     document_factory(meta={"position": 1})
@@ -26,3 +29,51 @@ def test_offset_pagination(db, schema_executor, document_factory):
     assert result.data["allDocuments"]["totalCount"] == 2
     assert result.data["allDocuments"]["edges"][0]["node"]["meta"]["position"] == 2
     assert result.data["allDocuments"]["edges"][1]["node"]["meta"]["position"] == 3
+
+
+@pytest.mark.parametrize(
+    "first,last,before,after,has_next,has_previous",
+    [
+        (1, None, None, None, True, False),
+        (None, 1, None, None, False, True),
+        (None, None, None, None, False, False),
+        (None, None, None, "YXJyYXljb25uZWN0aW9uOjI=", False, True),
+        (None, None, "YXJyYXljb25uZWN0aW9uOjI=", None, True, False),
+    ],
+)
+def test_has_next_previous(
+    db,
+    first,
+    last,
+    before,
+    after,
+    has_next,
+    has_previous,
+    schema_executor,
+    document_factory,
+):
+    document_factory.create_batch(5)
+
+    query = """
+        query AllDocumentsQuery ($first: Int, $last: Int, $before: String, $after: String) {
+          allDocuments(first: $first, last: $last, before: $before, after: $after) {
+            pageInfo {
+              hasNextPage
+              hasPreviousPage
+            }
+            edges {
+              node {
+                id
+              }
+            }
+          }
+        }
+    """
+
+    inp = {"first": first, "last": last, "before": before, "after": after}
+
+    result = schema_executor(query, variables=inp)
+
+    assert not result.errors
+    assert result.data["allDocuments"]["pageInfo"]["hasNextPage"] == has_next
+    assert result.data["allDocuments"]["pageInfo"]["hasPreviousPage"] == has_previous

caluma/core/types.py

@@ -1,7 +1,15 @@
+from collections import Iterable
+
 import graphene
 from django.core.exceptions import ImproperlyConfigured
 from django.db.models.query import QuerySet
+from graphene.relay import PageInfo
+from graphene.relay.connection import ConnectionField
 from graphene_django import types
+from graphene_django.fields import DjangoConnectionField
+from graphene_django.utils import maybe_queryset
+
+from .pagination import connection_from_list, connection_from_list_slice
 
 
 class Node(object):
@@ -54,3 +62,68 @@ def resolve_total_count(self, info, **kwargs):
         if isinstance(self.iterable, QuerySet):
             return self.iterable.count()
         return len(self.iterable)
+
+
+class DjangoConnectionField(DjangoConnectionField):
+    """
+    Custom DjangoConnectionField with fix for hasNextPage/hasPreviousPage.
+
+    This can be removed, when (or better if)
+    https://github.com/graphql-python/graphql-relay-py/issues/12
+    is resolved.
+    """
+
+    @classmethod
+    def resolve_connection(cls, connection, default_manager, args, iterable):
+        if iterable is None:
+            iterable = default_manager
+        iterable = maybe_queryset(iterable)
+        if isinstance(iterable, QuerySet):
+            if iterable is not default_manager:
+                default_queryset = maybe_queryset(default_manager)
+                iterable = cls.merge_querysets(default_queryset, iterable)
+            _len = iterable.count()
+        else:  # pragma: no cover
+            _len = len(iterable)
+        connection = connection_from_list_slice(
+            iterable,
+            args,
+            slice_start=0,
+            list_length=_len,
+            list_slice_length=_len,
+            connection_type=connection,
+            edge_type=connection.Edge,
+            pageinfo_type=PageInfo,
+        )
+        connection.iterable = iterable
+        connection.length = _len
+        return connection
+
+
+class ConnectionField(ConnectionField):
+    """
+    Custom ConnectionField with fix for hasNextPage/hasPreviousPage.
+
+    This can be removed, when (or better if)
+    https://github.com/graphql-python/graphql-relay-py/issues/12
+    is resolved.
+    """
+
+    @classmethod
+    def resolve_connection(cls, connection_type, args, resolved):
+        if isinstance(resolved, connection_type):  # pragma: no cover
+            return resolved
+
+        assert isinstance(resolved, Iterable), (
+            "Resolved value from the connection field have to be iterable or instance of {0}. "
+            'Received "{1}"'
+        ).format(connection_type, resolved)
+        connection = connection_from_list(
+            resolved,
+            args,
+            connection_type=connection_type,
+            edge_type=connection_type.Edge,
+            pageinfo_type=PageInfo,
+        )
+        connection.iterable = resolved
+        return connection

caluma/form/schema.py

@@ -1,12 +1,17 @@
 import graphene
-from graphene import ConnectionField, relay
+from graphene import relay
 from graphene.types import ObjectType, generic
 from graphene_django.rest_framework import serializer_converter
 
 from ..core.filters import DjangoFilterConnectionField, DjangoFilterSetConnectionField
 from ..core.mutation import Mutation, UserDefinedPrimaryKeyMixin
 from ..core.relay import extract_global_id
-from ..core.types import CountableConnectionBase, DjangoObjectType, Node
+from ..core.types import (
+    ConnectionField,
+    CountableConnectionBase,
+    DjangoObjectType,
+    Node,
+)
 from ..data_source.data_source_handlers import get_data_source_data
 from ..data_source.schema import DataSourceDataConnection
 from . import filters, models, serializers
@@ -168,7 +173,7 @@ class Meta:
 class TextQuestion(QuestionQuerysetMixin, FormDjangoObjectType):
     max_length = graphene.Int()
     placeholder = graphene.String()
-    format_validators = graphene.ConnectionField(FormatValidatorConnection)
+    format_validators = ConnectionField(FormatValidatorConnection)
 
     def resolve_format_validators(self, info):
         return get_format_validators(include=self.format_validators)
@@ -192,7 +197,7 @@ class Meta:
 class TextareaQuestion(QuestionQuerysetMixin, FormDjangoObjectType):
     max_length = graphene.Int()
     placeholder = graphene.String()
-    format_validators = graphene.ConnectionField(FormatValidatorConnection)
+    format_validators = ConnectionField(FormatValidatorConnection)
 
     def resolve_format_validators(self, info):
         return get_format_validators(include=self.format_validators)