Add gql compiler

Author: Naor Matania

README.md

@@ -41,6 +41,7 @@ The main features of GQL are:
 * Supports [File uploads](https://gql.readthedocs.io/en/latest/usage/file_upload.html)
 * [gql-cli script](https://gql.readthedocs.io/en/latest/gql-cli/intro.html) to execute GraphQL queries from the command line
 * [DSL module](https://gql.readthedocs.io/en/latest/advanced/dsl_module.html) to compose GraphQL queries dynamically
+* [Compiler](https://gql.readthedocs.io/en/latest/advanced/compiler.html) to compile query files to strongly typed classes
 
 ## Installation
 

docs/advanced/compiler.rst

@@ -0,0 +1,156 @@
+Compiling queries to strongly typed classes
+===========================================
+
+It is possible to create strongly typed classes for querying graphql based on graphql schema.
+It is similar to how other libraries generate code for API schema types like gRPC and Thrift.
+
+The compliation is very helpful for building GraphQL based SDK in a fast and safe way as it helps you guarantee the following:
+
+1. GraphQL queries are valid - Queries are now validated in compile time and not just in runtime
+2. Python usage of query classes is valid - Using static typing (like mypy - http://mypy-lang.org/)
+3. Changes over time in graphql schema doesn't break existing SDKs - You can use verify flag of the compiler and integrate it in your CI/CD
+
+Usage
+-----
+
+After installation you should compile your queries with running
+
+.. code-block:: bash
+
+    gql-compiler {schema_library} {graphql_library}
+
+* ``schema_library`` is where the folder where the graphql schema (or schemas) are located
+* ``graphql_library`` is where you locate then queries that you'd like to compile (``Query``, ``Mutation`` and ``Subscription`` are supported)
+
+Example:
+
+In the ``graphql_library`` create the file ``query.graphql``:
+
+.. code-block::
+
+    query DogQuery($id: String!) {
+        dog(id: $id) {
+            id
+            name
+            breed
+            age
+        }
+    }
+
+After compilation it will create the file ``query.py`` in the same
+folder:
+
+.. code-block:: python
+
+    #!/usr/bin/env python3
+    # @generated AUTOGENERATED file. Do not Change!
+
+    from dataclasses import dataclass, field
+    from gql_client.runtime.variables import encode_variables
+    from gql import gql, Client
+    from gql.transport.exceptions import TransportQueryError
+    from functools import partial
+    from numbers import Number
+    from typing import Any, AsyncGenerator, Dict, List, Generator, Optional
+    from time import perf_counter
+    from dataclasses_json import DataClassJsonMixin, config
+
+    from gql_client.runtime.enum_utils import enum_field_metadata
+    from .enum.dog_breed import DogBreed
+
+
+    # fmt: off
+    QUERY: List[str] = ["""
+    query DogQuery($id: String!) {
+        dog(id: $id) {
+            id
+            name
+            breed
+            age
+        }
+    }
+    """
+    ]
+
+
+    class DogQuery:
+        @dataclass(frozen=True)
+        class DogQueryData(DataClassJsonMixin):
+            @dataclass(frozen=True)
+            class Dog(DataClassJsonMixin):
+                id: str
+                name: Optional[str]
+                breed: Optional[DogBreed] = field(metadata=enum_field_metadata(DogBreed))
+                age: Optional[int]
+
+            dog: Optional[Dog]
+
+        # fmt: off
+        @classmethod
+        def execute(cls, client: Client, id: str) -> Optional[DogQueryData.Dog]:
+            variables: Dict[str, Any] = {"id": id}
+            new_variables = encode_variables(variables)
+            response_text = client.execute(
+                gql("".join(set(QUERY))), variable_values=new_variables
+            )
+            res = cls.DogQueryData.from_dict(response_text)
+            return res.dog
+
+        # fmt: off
+        @classmethod
+        async def execute_async(cls, client: Client, id: str) -> Optional[DogQueryData.Dog]:
+            variables: Dict[str, Any] = {"id": id}
+            new_variables = encode_variables(variables)
+            response_text = await client.execute_async(
+                gql("".join(set(QUERY))), variable_values=new_variables
+            )
+            res = cls.DogQueryData.from_dict(response_text)
+            return res.dog
+
+
+An example for using the generated class:
+
+.. code-block:: python
+
+    from gql import Client
+    from gql.transport.aiohttp import AIOHTTPTransport
+    from gql_client.runtime.graphql_client import GraphqlClient
+    from query import DogQuery
+
+    transport = AIOHTTPTransport(url="http://.../graph/query")
+    client = Client(transport=transport, fetch_schema_from_transport=True)
+    result = DogQuery.execute(client, id="1000")
+
+
+Custom Scalars
+--------------
+
+If your graphql schema contains custom scalars you should create python
+configuration file with the definitions of the custom scalars and use in
+the compilation command with ``--config_path`` option. In the
+configuration file you should have ``custom_scalars`` variable of type
+``Dict[str, CustomScalar]``. Simple example:
+
+.. code-block:: python
+
+    from gql_client.compiler.renderer_dataclasses import CustomScalar
+    from typing import Dict
+
+    custom_scalars: Dict[str, CustomScalar] = {
+        "Cursor": CustomScalar(
+            name="Cursor",
+            type=str,
+        ),
+    }
+
+
+CustomScalar also has ``encoder``, ``decoder`` and ``mm_field`` fields that can be used when the custom scalar is defined with complex type that requires encoding-decoding from the string that is being sent in the graphql response.
+
+More features
+-------------
+
+-  Create fragments query files and share them between other query files
+-  Compiler has an option to only verify compiled query files without
+   re-genrating them (``--verify`` option)
+-  Compiler can be configured to raise an error if queries use
+   deprecated fields (``--allow-deprecated`` option)

docs/advanced/index.rst

@@ -8,3 +8,4 @@ Advanced
    logging
    local_schema
    dsl_module
+   compiler

gql/compiler/__init__.py

@@ -0,0 +1,3 @@
+"""The :mod:`compiler` package includes compiler for compiling graphql query files to strongly typed classes.
+More details can be found in [Documentation](https://gql.readthedocs.io/en/latest/advanced/compiler.html)
+"""