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README.md

libgraphqlparser

libgraphqlparser is a parser for GraphQL, a query language for describing data requirements on complex application data models, implemented in C++11. It can be used on its own in C++ code (or in C code via the pure C API defined in the c subdirectory), or you can use it as the basis for an extension module for your favorite programming language instead of writing your own parser from scratch.

Example

The provided dump_json_ast is a simple program that reads GraphQL text on stdin and prints a JSON representation of the AST to stdout.

The python subdirectory contains an example Python binding for the pure C API.

Requirements

libgraphqlparser requires a C++ compiler that supports C++11. It also requires Mac OS X or Linux.

To run tests, first, compile and install the library as described above. Then, please download googletest from https://github.com/google/googletest/archive/release-1.8.0.zip and unzip it in the test subdirectory. In consequence, a folder googletest-release-1.8.0 should be contained in test. Next, within the test folder, run cmake . and make to generate the runTests binary. To execute the tests run ./test/runTests from the main folder.

Building libgraphqlparser

libgraphqlparser is built with CMake. If a sufficiently-recent version of Flex and Bison are installed on your system, it will use them; otherwise, it will rely on the checked-in parser.tab.{c,h}pp and lexer.{h,cpp}.

To build libgraphqlparser from source:

$ # inside the project root:
$ cmake .
$ make

Then, to install it on your system:

$ make install

How libgraphqlparser works

libgraphqlparser uses flex and bison to generate a C++ parser for GraphQL. These tools work well but have idiosyncratic interfaces by modern standards, so GraphQLParser.h provides a simple interface to parse GraphQL.

In order to make it simpler to write code based around the GraphQL AST, libgraphqlparser includes an extremely simple code generation framework in the ast/ subdirectory. This framework is used to build the AST classes themselves, as well as a visitor over the AST. It may be easier to understand the output of the generation steps directly (i.e., Ast.h, Ast.cpp, and AstVisitor.h) rather than trying to read the generation scripts. Simply building libgraphqlparser will cause these files to be generated.

libgraphqlparser also uses the AST generation framework to build a pure C API in the c subdirectory. This API can be used from C code, and it should also simplify the task of creating bindings to other programming languages.

License

libgraphqlparser is MIT-licensed.

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