Introduction

GraphQL and React go together like peanut butter and jelly, especially if you use a GraphQL client/compiler like Relay or Apollo.

But GraphQL services are only implemented on the server. When using React Native or React JS in a hybrid application, you typically have a native application which hosts islands or entire pages of UI rendered with React components, and you might like to display content that you've cached offline or that you otherwise generate on the client without needing to declare a separate data interface or require a server round trip to load it.

This project includes a graphqlservice library with the core functionality of a GraphQL service and a schemagen utility to generate types for your custom GraphQL service schema definition. Once you implement the pure virtual methods on the object interfaces and add hooks to the Relay Network Layer/Apollo Terminating Link to call your service, you can use the same GraphQL client code to access your native data source or a GraphQL service online. You might even be able to share some more of that code between a progressive web app and your native/hybrid app.

If what you're after is a way to consume a GraphQL service from C++, this project also includes a graphqlclient library and a clientgen utility to generate types matching a GraphQL request document, its variables, and all of the serialization code you need to talk to a graphqlservice implementation. If you want to consume another service, you will need access to the schema definition (rather than the Introspection query results), and you will need be able to send requests along with any variables to the service and parse its responses into a graphql::response::Value (e.g. with the graphqljson library) in your code.

Related projects

The most complete examples I've built are related to GqlMAPI:

• eMAPI: Windows-only Electron app which lets you access the MAPI interface used by Microsoft Outlook. Its goal is to be a spiritual successor to a debugging and diagnostic tool called MFCMAPI.
• electron-gqlmapi: Native module for Electron which hosts GqlMAPI in eMAPI. It includes JS libraries for calling the native module across the Electron IPC channel.
• Tauri-GqlMAPI: Reimplementation of eMAPI built in Rust and TypeScript on top of Tauri.
• gqlmapi-rs: Rust crate I built to expose safe bindings for GqlMAPI. It is loosely based on electron-gqlmapi, and it is used by Tauri-GqlMAPI.

I created a couple of sample projects to demonstrate integrating the schema.today.graphql service into an Electron app. The schema.today.graphql schema and service implementation in TodayMock.* are focused on testing, so the specific bootstrapping used in these projects should not be re-used, but you can use them as a scaffold to start your own integration with Electron or Node.js. They're available under my personal account, and I recently updated them to match the latest release of cppgraphqlgen:

• electron-cppgraphql: Node Native Module which compiles against the version of the Node headers included in Electron. This was the starting point for electron-gqlmapi, and it is still useful as a sample because it does not depend on a platform-specific API like MAPI, so it works cross-platform.
• cppgraphiql: Electron app which consumes electron-cppgraphql and exposes an instance of GraphiQL on top of it.

Feel free to use either or both of these as a starting point to integrate your own generated service with Node, Electron, or Tauri. PRs with links to your own samples are always welcome.

Getting Started

Installation process

The minimum OS and toolchain versions I've tested with this version of cppgraphqlgen are:

• Microsoft Windows: Visual Studio 2019
• Linux: Ubuntu 20.04 LTS with gcc 10.3.0
• macOS: 11 (Big Sur) with AppleClang 13.0.0.

The key compiler requirement is support for C++20 including coroutines and concepts. Some of these compiler versions still treat coroutine support as experimental, and the CMake configuration can auto-detect that, but earlier versions of gcc and clang do not seem to have enough support for C++20.

The easiest way to build and install cppgraphqlgen is to use microsoft/vcpkg. See the Getting Started section of the vcpkg README for details. Once you have that configured, run vcpkg install cppgraphqlgen (or cppgraphqlgen:x64-windows, cppgraphqlgen:x86-windows-static, etc. depending on your platform). That will build and install all of the dependencies for cppgraphqlgen, and then build cppgraphqlgen itself without any other setup. The cppgraphqlgen package (and its dependencies) are advertised to the CMake find_package function through the -DCMAKE_TOOLCHAIN_FILE=<...>/scripts/buildsystems/vcpkg.cmake parameter/variable. There are more details about this in the vcpkg documentation.

If you want to build cppgraphqlgen yourself, you can do that with CMake from a clone or archive of this repo. See the Build and Test section below for instructions. You will need to install the dependencies first where find_package can find them. If vcpkg works otherwise, you can do that with vcpkg install pegtl boost-program-options rapidjson gtest. Some of these are optional, if for example you do not build the tests. If vcpkg does not work, please see the documentation for each of those dependencies, as well as your platform/toolchain documentation for perferred installation mechanisms. You may need to build some or all of them separately from source.

Software dependencies

The build system for this project uses CMake. You will need to have CMake (at least version 3.15.0) installed, and the library dependencies need to be where CMake can find them. Otherwise you need to disable the options which depend on them.

Besides the MIT license for this project, if you redistribute any source code or binaries built from these library dependencies, you should still follow the terms of their individual licenses. As of this writing, this library and all of its dependencies are available under either the MIT License or the Boost Software License (BSL). Both licenses roughly mean that you may redistribute them freely as long as you include an acknowledgement along with the license text. Please see the license or copyright notice which comes with each project for more details.

graphqlpeg

• GraphQL parsing: Parsing Expression Grammar Template Library (PEGTL) release 3.2.6, which is part of The Art of C++ library collection. I've added this as a sub-module, so you do not need to install this separately. If you already have 3.2.6 installed where CMake can find it, it will use that instead of the sub-module and avoid installing another copy of PEGTL.

graphqlservice

The core library depends on graphqlpeg and it references the PEGTL headers itself at build time. Both of those mean it depends on PEGTL as well.

graphqljson (GRAPHQL_USE_RAPIDJSON=ON)

• JSON support: RapidJSON release 1.1.0. If you don't need JSON support, you can also avoid installing this dependency. You will need to set GRAPHQL_USE_RAPIDJSON=OFF in your CMake configuration to do that.

schemagen

I'm using Boost for schemagen:

• Command line handling: Boost.Program_options. Run schemagen -? to get a list of options. Many of the files in the samples directory were generated with schemagen, you can look at samples/CMakeLists.txt for a few examples of how to call it:

Usage:  schemagen [options] <schema file> <output filename prefix> <output namespace>
Command line options:
  --version              Print the version number
  -? [ --help ]          Print the command line options
  -v [ --verbose ]       Verbose output including generated header names as
                         well as sources
  -s [ --schema ] arg    Schema definition file path
  -p [ --prefix ] arg    Prefix to use for the generated C++ filenames
  -n [ --namespace ] arg C++ sub-namespace for the generated types
  --source-dir arg       Target path for the <prefix>Schema.cpp source file
  --header-dir arg       Target path for the <prefix>Schema.h header file
  --stubs                Unimplemented fields throw runtime exceptions instead
                         of compiler errors
  --no-introspection     Do not generate support for Introspection

I've tested this with several versions of Boost going back to 1.65.0. I expect it will work fine with most versions of Boost after that. The Boost dependencies are only used by the schemagen utility at or before your build, so you probably don't need to redistribute it or the Boost libraries with your project.

If you are building shared libraries on Windows (DLLs) using vcpkg or BUILD_SHARED_LIBS=ON in CMake, be aware that this adds a runtime dependency on a Boost DLL. The schemagen tool won't run without it. However, in addition to automating the install of Boost, vcpkg also takes care of installing the dependencies next to schemagen.exe when building the Windows and UWP shared library targets (the platform triplets which don't end in -static).

clientgen

The clientgen utility is based on schemagen and shares the same external dependencies. The command line arguments are almost the same, except it takes an extra file for the request document and there is no equivalent to --stubs:

Usage:  clientgen [options] <schema file> <request file> <output filename prefix> <output namespace>
Command line options:
  --version              Print the version number
  -? [ --help ]          Print the command line options
  -v [ --verbose ]       Verbose output including generated header names as
                         well as sources
  -s [ --schema ] arg    Schema definition file path
  -r [ --request ] arg   Request document file path
  -o [ --operation ] arg Operation name if the request document contains more
                         than one
  -p [ --prefix ] arg    Prefix to use for the generated C++ filenames
  -n [ --namespace ] arg C++ sub-namespace for the generated types
  --source-dir arg       Target path for the <prefix>Client.cpp source file
  --header-dir arg       Target path for the <prefix>Client.h header file
  --no-introspection     Do not expect support for Introspection

This utility should output one header and one source file for each request document. A request document may contain more than one operation, in which case it will output definitions for all of them together. You may limit the output to a single operation from the request document by specifying the --operation (or -o) argument with the operation name.

The generated code depends on the graphqlclient library for serialization of built-in types. If you link the generated code, you'll also need to link graphqlclient, graphqlpeg for the pre-parsed, pre-validated request AST, and graphqlresponse for the graphql::response::Value implementation.

Sample output for clientgen is in the sub-directories of samples/client, and several of them are consumed by unit tests in test/ClientTests.cpp.

tests (GRAPHQL_BUILD_TESTS=ON)

• Unit testing: Google Test for the unit testing framework. If you don't want to build or run the unit tests, you can avoid this dependency as well by setting GRAPHQL_BUILD_TESTS=OFF in your CMake configuration.

API references

See GraphQLService.h for the base types implemented in the graphql::service namespace.

Take a look at the samples/learn directory, starting with StarWarsData.cpp to see a sample implementation of a custom schema defined in schema.learn.graphql. This is the same schema and sample data used in the GraphQL tutorial on https://graphql.org/learn/. This directory builds an interactive command line application which can execute query and mutation operations against the sample data in memory.

There are several helper functions for CMake declared in cmake/cppgraphqlgen-functions.cmake, which is automatically included if you use find_package(cppgraphqlgen) in your own CMake project. See samples/learn/schema/CMakeLists.txt and samples/learn/CMakeLists.txt, or the CMakeLists.txt files in some of the other samples sub-directories for examples of how to use them to automatically rerun the code generators and update the files in your source directory.

Migrating from v3.x to main

Please see the Migration Guide for v4.x for more details about upgrading to from the v3.x branch to the main branch. Active development takes place almost entirely in main.

Additional Documentation

There are some more targeted documents in the doc directory:

• Awaitable Types
• Parsing GraphQL
• Query Responses
• JSON Representation
• Field Resolvers
• Field Parameters
• Directives
• Subscriptions

Samples

All of the samples are under samples, with nested sub-directories for generated files:

• samples/today: There are two different samples generated from schema.today.graphql in this directory. The default schema target includes Introspection support (which is the default), while the nointrospection target demonstrates how to disable Introspection support with the schemagen --no-introspection parameter. The mock implementation of the service for both schemas is in samples/today/TodayMock.h and samples/today/TodayMock.cpp. It builds an interactive sample/sample_nointrospection and benchmark/benchmark_nointrospection target for each version, and it uses each of them in several unit tests.
• samples/client: Several sample queries built with clientgen against the schema.today.graphql schema shared with samples/today. It includes a client_benchmark executable for comparison with benchmark executables using the same hardcoded query in [samples/today/]. The benchmark links with the default schema target in samples/today to handle the benchmark query.
• samples/learn: Simpler standalone which builds a learn_star_wars executable that follows the tutorial examples on https://graphql.org/learn/.
• samples/validation: This schema is based on the examples and counter-examples from the Validation section of the October 2021 GraphQL spec. There is no implementation of this schema, it relies entirely generated stubs (created with schemagen --stubs) to build successfully without defining more than placeholder objects fo the Query, Mutation, and Subscription operations in samples/validation/ValidationMock.h. It is used to test the validation logic with every example or counter-example in the spec in test/ValidationTests.cpp.
• samples/proxy (GRAPHQL_BUILD_HTTP_SAMPLE=ON): Generates a client and server pair of executables which proxy requests from the client to the server over HTTP (on port 8080 for localhost). The HTTP support in both samples comes from Boost.Beast, which must be included in your Boost installation to build this directory. If you are using vcpkg, it will install the necessary Boost components on demand. Note: This directory uses the Boost Software License because the samples borrow heavily from examples in the Boost.Beast documentation.

Build and Test

Visual Studio on Windows

Use the Open Folder command to open the root of the repo. If you've installed the dependencies with vcpkg and run its Visual Studio integration command, Visual Studio should know how to build each of the targets in this project automatically.

Once you've built the project Visual Studio's Test Explorer window should list the unit tests, and you can run all of them from there.

Command Line on any platform

Your experience will vary depending on your build toolchain. The same instructions should work for any platform that CMake supports. These basic steps will build and run the tests. You can add options to build in another target directory, change the config from Debug (default) to Release, use another build tool like Ninja, etc. If you are using vcpkg to install the dependencies, remember to specify the -DCMAKE_TOOLCHAIN_FILE=... option when you run the initial build configuration.

• Create a build directory: "mkdir build && cd build"
• Configure the build system: "cmake .."
• Tell CMake to invoke the build system: "cmake --build ." You can repeat this step to rebuild your changes.
• CTest comes with CMake and runs the tests: "ctest ." Run this frequently, and make sure it passes before commits.

You can then optionally install the public outputs by configuring it with Release:

• cmake -DCMAKE_BUILD_TYPE=Release ..
• cmake --build . --target install You probably need to use sudo on Unix to do this.

Interactive tests

If you want to try an interactive version, you can run samples/today/sample or samples/today/sample_nointrospection and paste in queries against the same mock service or load a query from a file on the command line.

Reporting Security Issues

Security issues and bugs should be reported privately, via email, to the Microsoft Security Response Center (MSRC) at [email protected]. You should receive a response within 24 hours. If for some reason you do not, please follow up via email to ensure we received your original message. Further information, including the MSRC PGP key, can be found in the Security TechCenter.

Contributing

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.microsoft.com.

When you submit a pull request, a CLA-bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., label, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact [email protected] with any additional questions or comments.