Add field dependencies

.github/workflows/tests.yml

@@ -29,6 +29,6 @@ jobs:
         pytest
     - name: Linters
       run: |
-        ruff ariadne_graphql_proxy tests
+        ruff check ariadne_graphql_proxy tests
         mypy ariadne_graphql_proxy --ignore-missing-imports --check-untyped-defs
         black --check ariadne_graphql_proxy tests

CHANGELOG.md

@@ -1,10 +1,11 @@
 # CHANGELOG
 
-## UNRELEASED
+## 0.3.0 (UNRELEASED)
 
 - Added `CacheSerializer`, `NoopCacheSerializer` and `JSONCacheSerializer`. Changed `CacheBackend`, `InMemoryCache`, `CloudflareCacheBackend` and `DynamoDBCacheBackend` to accept `serializer` initialization option.
 - Fixed schema proxy returning an error when variable defined in an operation is missing from its variables.
 - Improved custom headers handling in `ProxyResolver` and `ProxySchema`.
+- Added fields dependencies configuration option to `ProxySchema`.
 
 
 ## 0.2.0 (2023-09-25)

GUIDE.md

@@ -572,6 +572,71 @@ If `proxy_headers` is a callable, it will be called with single argument (`conte
 If `proxy_headers` is `None` or `False`, no headers are proxied to the other service.
 
 
+## Fields dependencies
+
+In situations where field depends on data from sibling fields in order to be resolved, `ProxySchema` can be configured to include those additional fields in root value query sent to remote schema.
+
+Below example pulls a remote schema that defines `Product` type, extends this type with `image: String` field, and then uses `ProxySchema.add_field_dependencies` to configure `{ metadata { thumb} }` as additional fields to retrieve when `image` field is queried. It also includes custom resolver for `image` field that uses this additional data:
+
+
+```python
+from ariadne.asgi import GraphQL
+from ariadne_graphql_proxy import (
+    ProxySchema,
+    get_context_value,
+    set_resolver,
+)
+from graphql import build_ast_schema, parse
+
+
+proxy_schema = ProxySchema()
+
+# Store schema ID for remote schema
+remote_schema_id = proxy_schema.add_remote_schema(
+    "https://example.com/graphql/",
+)
+
+# Extend Product type with additional image field
+proxy_schema.add_schema(
+    build_ast_schema(
+        parse(
+            """
+            type Product {
+                image: String
+            }
+            """
+        )
+    )
+)
+
+# Configure proxy schema to retrieve thumb from metadata
+# from remote schema when image is queried
+proxy_schema.add_field_dependencies(
+    remote_schema_id, "Product", "image", "{ metadata { thumb } }"
+)
+
+# Create schema instance
+final_schema = proxy_schema.get_final_schema()
+
+
+# Add product image resolver
+def resolve_product_image(obj, info):
+    return obj["metadata"]["thumb"]
+
+
+set_resolver(final_schema, "Product", "image", resolve_product_image)
+
+
+# Setup Ariadne ASGI GraphQL application
+app = GraphQL(
+    final_schema,
+    context_value=get_context_value,
+    root_value=proxy_schema.root_resolver,
+    debug=True,
+)
+```
+
+
 ## Cache framework
 
 Ariadne GraphQL Proxy implements basic cache framework that enables of caching parts of GraphQL queries.
@@ -855,6 +920,34 @@ def add_delayed_fields(self, delayed_fields: Dict[str, List[str]]):
 Sets specific fields in schema as delayed. Delayed fields are excluded from queries ran by `root_resolver` against the remote GraphQL APIs.
 
 
+#### `delayed_fields`
+
+This is a dict of type name and fields names lists:
+
+```python
+{"Type": ["field", "otherField"], "OtherType": ["field"]}
+```
+
+
+### `add_field_dependencies`
+
+```python
+def add_field_dependencies(
+    self, schema_id: int, type_name: str, field_name: str, query: str
+):
+```
+
+Adds fields specified in `query` as dependencies for `field_name` of `type_name` that should be retrieved from schema with `schema_id`.
+
+
+#### Required arguments
+
+- `schema_id`: an `int` with ID of schema returned by `add_remote_schema` or `add_schema`.
+- `type_name`: a `str` with name of type for which dependencies will be set.
+- `field_name`: a `str` with name of field which dependencies will be set.
+- `query`: a `str` with additional fields to fetch when `field_name` is included, eg. `{ metadata { key value} }`.
+
+
 ### `add_foreign_key`
 
 ```python

ariadne_graphql_proxy/__init__.py

@@ -44,6 +44,7 @@
 from .query_filter import QueryFilter, QueryFilterContext
 from .remote_schema import get_remote_schema
 from .resolvers import set_resolver, unset_resolver
+from .selections import merge_selection_sets, merge_selections
 
 __all__ = [
     "ForeignKeyResolver",
@@ -84,6 +85,8 @@
     "merge_objects",
     "merge_scalars",
     "merge_schemas",
+    "merge_selection_sets",
+    "merge_selections",
     "merge_type_maps",
     "merge_types",
     "merge_unions",

ariadne_graphql_proxy/proxy_schema.py

@@ -11,6 +11,10 @@
     GraphQLSchema,
     GraphQLUnionType,
     GraphQLWrappingType,
+    OperationDefinitionNode,
+    OperationType,
+    SelectionSetNode,
+    parse,
     print_ast,
 )
 from httpx import AsyncClient
@@ -20,6 +24,7 @@
 from .proxy_root_value import ProxyRootValue
 from .query_filter import QueryFilter
 from .remote_schema import get_remote_schema
+from .selections import merge_selection_sets
 from .standard_types import STANDARD_TYPES, add_missing_scalar_types
 from .str_to_field import (
     get_field_definition_from_str,
@@ -46,6 +51,7 @@ def __init__(
         self.fields_types: Dict[str, Dict[str, str]] = {}
         self.unions: Dict[str, List[str]] = {}
         self.foreign_keys: Dict[str, Dict[str, List[str]]] = {}
+        self.dependencies: Dict[int, Dict[str, Dict[str, SelectionSetNode]]] = {}
 
         self.proxy_root_value = proxy_root_value
 
@@ -176,8 +182,105 @@ def add_foreign_key(
         if field_name in self.foreign_keys[type_name]:
             raise ValueError(f"Foreign key already exists on {type_name}.{field_name}")
 
+        for schema_dependencies in self.dependencies.values():
+            if (
+                type_name in schema_dependencies
+                and field_name in schema_dependencies[type_name]
+            ):
+                raise ValueError(
+                    f"Foreign key can't be created for {type_name}.{field_name} because "
+                    "field dependencies were previously defined for it."
+                )
+
         self.foreign_keys[type_name][field_name] = [on] if isinstance(on, str) else on
 
+    def add_field_dependencies(
+        self, schema_id: int, type_name: str, field_name: str, query: str
+    ):
+        if type_name in ("Query", "Mutation", "Subscription"):
+            raise ValueError(
+                f"Defining field dependencies for {type_name} fields is not allowed."
+            )
+
+        if (
+            type_name in self.foreign_keys
+            and field_name in self.foreign_keys[type_name]
+        ):
+            raise ValueError(
+                f"Dependencies can't be created for {type_name}.{field_name} because "
+                "foreign key was previously defined for it."
+            )
+
+        if schema_id < 0 or schema_id + 1 > len(self.urls):
+            raise ValueError(f"Schema with ID '{schema_id}' doesn't exist.")
+        if not self.urls[schema_id]:
+            raise ValueError(f"Schema with ID '{schema_id}' is not a remote schema.")
+
+        schema = self.schemas[schema_id]
+        if type_name not in schema.type_map:
+            raise ValueError(
+                f"Type '{type_name}' doesn't exist in schema with ID '{schema_id}'."
+            )
+
+        schema_type = schema.type_map[type_name]
+        if not isinstance(schema_type, GraphQLObjectType):
+            raise ValueError(
+                f"Type '{type_name}' in schema with ID '{schema_id}' is not "
+                "an object type."
+            )
+
+        self.validate_field_with_dependencies(type_name, field_name)
+
+        if schema_id not in self.dependencies:
+            self.dependencies[schema_id] = {}
+        if type_name not in self.dependencies[schema_id]:
+            self.dependencies[schema_id][type_name] = {}
+
+        selection_set = self.parse_field_dependencies(field_name, query)
+
+        type_dependencies = self.dependencies[schema_id][type_name]
+        if not type_dependencies.get(field_name):
+            type_dependencies[field_name] = selection_set
+        else:
+            type_dependencies[field_name] = merge_selection_sets(
+                type_dependencies[field_name], selection_set
+            )
+
+    def parse_field_dependencies(self, field_name: str, query: str) -> SelectionSetNode:
+        clean_query = query.strip()
+        if not clean_query.startswith("{") or not clean_query.endswith("}"):
+            raise ValueError(
+                f"'{field_name}' field dependencies should be defined as a single "
+                "GraphQL operation, e.g.: '{ field other { subfield } }'."
+            )
+
+        ast = parse(clean_query)
+
+        if (
+            not len(ast.definitions) == 1
+            or not isinstance(ast.definitions[0], OperationDefinitionNode)
+            or ast.definitions[0].operation != OperationType.QUERY
+        ):
+            raise ValueError(
+                f"'{field_name}' field dependencies should be defined as a single "
+                "GraphQL operation, e.g.: '{ field other { subfield } }'."
+            )
+
+        return ast.definitions[0].selection_set
+
+    def validate_field_with_dependencies(self, type_name: str, field_name: str) -> None:
+        for schema in self.schemas:
+            if (
+                type_name in schema.type_map
+                and isinstance(schema.type_map[type_name], GraphQLObjectType)
+                and field_name in schema.type_map[type_name].fields  # type: ignore
+            ):
+                return
+
+        raise ValueError(
+            f"Type '{type_name}' doesn't define the '{field_name}' field in any of schemas."
+        )
+
     def add_delayed_fields(self, delayed_fields: Dict[str, List[str]]):
         for type_name, type_fields in delayed_fields.items():
             if type_name not in self.fields_map:
@@ -227,6 +330,7 @@ def get_final_schema(self) -> GraphQLSchema:
             self.fields_types,
             self.unions,
             self.foreign_keys,
+            self.dependencies,
         )
 
         return self.schema

ariadne_graphql_proxy/query_filter.py

@@ -14,6 +14,8 @@
     VariableNode,
 )
 
+from .selections import merge_selections
+
 
 class QueryFilterContext:
     schema_id: int
@@ -35,13 +37,15 @@ def __init__(
         fields_types: Dict[str, Dict[str, str]],
         unions: Dict[str, List[str]],
         foreign_keys: Dict[str, Dict[str, List[str]]],
+        dependencies: Dict[int, Dict[str, Dict[str, SelectionSetNode]]],
     ):
         self.schema = schema
         self.schemas = schemas
         self.fields_map = fields_map
         self.fields_types = fields_types
         self.unions = unions
         self.foreign_keys = foreign_keys
+        self.dependencies = dependencies
 
     def split_query(
         self, document: DocumentNode
@@ -189,12 +193,22 @@ def filter_field_node(
         else:
             type_fields = self.fields_map[type_name]
 
+        fields_dependencies = self.get_type_fields_dependencies(
+            context.schema_id, type_name
+        )
+
         new_selections: List[SelectionNode] = []
         for selection in field_node.selection_set.selections:
             if isinstance(selection, FieldNode):
+                field_name = selection.name.value
+                if fields_dependencies and field_name in fields_dependencies:
+                    new_selections = merge_selections(
+                        new_selections, fields_dependencies[field_name].selections
+                    )
+
                 if (
-                    selection.name.value not in type_fields
-                    or context.schema_id not in type_fields[selection.name.value]
+                    field_name not in type_fields
+                    or context.schema_id not in type_fields[field_name]
                 ):
                     continue
 
@@ -244,12 +258,22 @@ def filter_inline_fragment_node(
         type_name = fragment_node.type_condition.name.value
         type_fields = self.fields_map[type_name]
 
+        fields_dependencies = self.get_type_fields_dependencies(
+            context.schema_id, type_name
+        )
+
         new_selections: List[SelectionNode] = []
         for selection in fragment_node.selection_set.selections:
             if isinstance(selection, FieldNode):
+                field_name = selection.name.value
+                if fields_dependencies and field_name in fields_dependencies:
+                    new_selections = merge_selections(
+                        new_selections, fields_dependencies[field_name].selections
+                    )
+
                 if (
-                    selection.name.value not in type_fields
-                    or context.schema_id not in type_fields[selection.name.value]
+                    field_name not in type_fields
+                    or context.schema_id not in type_fields[field_name]
                 ):
                     continue
 
@@ -294,12 +318,22 @@ def filter_fragment_spread_node(
         type_name = fragment.type_condition.name.value
         type_fields = self.fields_map[type_name]
 
+        fields_dependencies = self.get_type_fields_dependencies(
+            context.schema_id, type_name
+        )
+
         new_selections: List[SelectionNode] = []
         for selection in fragment.selection_set.selections:
             if isinstance(selection, FieldNode):
+                field_name = selection.name.value
+                if fields_dependencies and field_name in fields_dependencies:
+                    new_selections = merge_selections(
+                        new_selections, fields_dependencies[field_name].selections
+                    )
+
                 if (
-                    selection.name.value not in type_fields
-                    or context.schema_id not in type_fields[selection.name.value]
+                    field_name not in type_fields
+                    or context.schema_id not in type_fields[field_name]
                 ):
                     continue
 
@@ -347,3 +381,13 @@ def inline_fragment_spread_node(
                 selections=tuple(selections),
             ),
         )
+
+    def get_type_fields_dependencies(
+        self,
+        schema_id: int,
+        type_name: str,
+    ) -> Optional[Dict[str, SelectionSetNode]]:
+        if schema_id in self.dependencies and type_name in self.dependencies[schema_id]:
+            return self.dependencies[schema_id][type_name]
+
+        return None