Merge pull request #24 from preply/provides-support

Provides support

Author: erebus1

README.md

@@ -28,9 +28,18 @@ Supports now:
 * extend  # extend remote types
 * external  # mark field as external 
 * requires  # mark that field resolver requires other fields to be pre-fetched
-
-Todo implement:
-* @provides
+* provides  # to annotate the expected returned fieldset from a field on a base type that is guaranteed to be selectable by the gateway. 
+    * **Base class should be decorated with `@provides`** as well as field on a base type that provides. Check example bellow:
+    ```python
+        import graphene
+        from graphene_federation import provides
+        
+        @provides
+        class ArticleThatProvideAuthorAge(graphene.ObjectType):
+            id = Int(required=True)
+            text = String(required=True)
+            author = provides(Field(User), fields='age')
+    ```
 
 
 ```python

graphene_federation/__init__.py

@@ -1,3 +1,4 @@
 from .main import build_schema
 from .entity import key
 from .extend import extend, external, requires
+from .provides import provides

graphene_federation/provides.py

@@ -0,0 +1,19 @@
+from graphene import Field
+
+provides_parent_types = set()
+
+
+def provides(field, fields: str = None):
+    """
+
+    :param field: base type (when used as decorator) or field of base type
+    :param fields:
+    :return:
+    """
+    if fields is None:  # used as decorator on base type
+        if isinstance(field, Field):
+            raise RuntimeError("Please specify fields")
+        provides_parent_types.add(field)
+    else:  # used as wrapper over field
+        field._provides = fields
+    return field

graphene_federation/service.py

@@ -4,6 +4,7 @@
 from graphene.utils.str_converters import to_camel_case
 
 from graphene_federation.extend import extended_types
+from graphene_federation.provides import provides_parent_types
 from .entity import custom_entities
 
 
@@ -37,6 +38,13 @@ def _mark_requires(entity_name, entity, schema, auto_camelcase):
     )
 
 
+def _mark_provides(entity_name, entity, schema, auto_camelcase):
+    return _mark_field(
+        entity_name, entity, schema, '_provides', lambda fields: f'@provides(fields: "{fields}")',
+        auto_camelcase
+    )
+
+
 def get_sdl(schema, custom_entities):
     string_schema = str(schema)
     string_schema = string_schema.replace("\n", " ")
@@ -51,6 +59,10 @@ def get_sdl(schema, custom_entities):
         pattern = re.compile(type_def_re)
         string_schema = pattern.sub(repl_str, string_schema)
 
+    for entity in provides_parent_types:
+        string_schema = _mark_provides(
+            entity.__name__, entity, string_schema, schema.auto_camelcase)
+
     for entity_name, entity in extended_types.items():
         string_schema = _mark_external(entity_name, entity, string_schema, schema.auto_camelcase)
         string_schema = _mark_requires(entity_name, entity, string_schema, schema.auto_camelcase)

integration_tests/service_b/src/schema.py

@@ -31,6 +31,10 @@ def __resolve_reference(self, info, **kwargs):
 class User(ObjectType):
     id = Int(required=True)
     primary_email = String()
+    age = Int()
+
+    def resolve_age(self, info):
+        return 17
 
     def __resolve_reference(self, info, **kwargs):
         if self.id is not None:

integration_tests/service_c/src/schema.py

@@ -1,16 +1,20 @@
 from graphene import ObjectType, String, Int, List, NonNull, Field
-from graphene_federation import build_schema, extend, external, requires, key
+from graphene_federation import build_schema, extend, external, requires, key, provides
 
 
 @extend(fields='id')
 class User(ObjectType):
     id = external(Int(required=True))
     primary_email = external(String())
     uppercase_email = requires(String(), fields='primaryEmail')
+    age = external(Int())
 
     def resolve_uppercase_email(self, info):
         return self.primary_email.upper() if self.primary_email else self.primary_email
 
+    def resolve_age(self, info):
+        return 18
+
 
 @key(fields='id')
 class Article(ObjectType):
@@ -22,13 +26,32 @@ def __resolve_reference(self, info, **kwargs):
         return Article(id=self.id, text=f'text_{self.id}')
 
 
+@provides
+class ArticleThatProvideAuthorAge(ObjectType):
+    """
+    should not contain other graphene-federation decorators to proper test test-case
+    """
+    id = Int(required=True)
+    text = String(required=True)
+    author = provides(Field(User), fields='age')
+
+    def __resolve_reference(self, info, **kwargs):
+        return Article(id=self.id, text=f'text_{self.id}')
+
+
 class Query(ObjectType):
     articles = List(NonNull(lambda: Article))
+    articles_with_author_age_provide = List(NonNull(lambda: ArticleThatProvideAuthorAge))
 
     def resolve_articles(self, info):
         return [
             Article(id=1, text='some text', author=User(id=5))
         ]
 
+    def resolve_articles_with_author_age_provide(self, info):
+        return [
+            ArticleThatProvideAuthorAge(id=1, text='some text', author=User(id=5))
+        ]
+
 
 schema = build_schema(Query)

integration_tests/tests/tests/test_main.py

@@ -145,3 +145,47 @@ def test_requires():
 
     assert articles == [
         {'id': 1, 'text': 'some text', 'author': {'uppercaseEmail': '[email protected]'}}]
+
+
+def test_provides():
+    """
+    articles -> w/o provide (get age value from service b)
+    articlesWithAuthorAgeProvide -> w/ provide (get age value from service c)
+
+    :return:
+    """
+    query = {
+        'query': """
+                query {
+                    articles {
+                        id
+                        text
+                        author {
+                            age
+                        }
+                    }
+                    articlesWithAuthorAgeProvide {
+                        id
+                        text
+                        author {
+                            age
+                        }
+                    }
+                }
+            """,
+        'variables': {}
+    }
+    response = requests.post(
+        'http://federation:3000/graphql/',
+        json=query,
+    )
+    assert response.status_code == 200
+    data = json.loads(response.content)['data']
+    articles = data['articles']
+    articles_with_age_provide = data['articlesWithAuthorAgeProvide']
+
+    assert articles == [
+        {'id': 1, 'text': 'some text', 'author': {'age': 17}}]
+
+    assert articles_with_age_provide == [
+        {'id': 1, 'text': 'some text', 'author': {'age': 18}}]