Graphql parser based on libgraphqlparser

Python2.7+ Python3.4+ class-based bindings to libgraphqlparser; just a thin layer on top of libgraphqlparser C API.

Still EXPERIMENTAL

Installing

First install libgraphqlparser following instructions on libgraphqlparser github page .

Next you can install graphqlparser. The easiest way is using precompiled wheels which are usually available on graphqlparser github releases

Pick the right wheel for your platform and python version, then install it using pip:

pip install https://github.com/elastic-coders/py-graphqlparser/releases/download/v0.0.4/graphqlparser-0.0.4-cp36-cp36m-linux_x86_64.whl

As an alternative you can install graphqlparser from source distribution:

• Install cython

• Set an env var $GRAPHQL_HOME to the folder where libgraphqlparser.so and Ast.h are

• Install graphqlparser with pip:

  LDFLAGS="-L$GRAPHQL_HOME" CFLAGS="-I$GRAPHQL_HOME/c -I$GRAPHQL_HOME" pip install graphqlparser
  

Usage

Make sure libgraphqlparser is available to the loader. You can add its base dir to LD_LIBRARY_PATH.

Then you can start parsing by creating your custom visitor class:

from graphql_parser import GraphQLAstVisitor

class MyVisitor(GraphQLAstVisitor.GraphQLAstVisitor):

    def visit_field(self, node):
        print('start field %s visit' % node)
        # Return 1 to keep visiting children, 0 to skip them
        return 1

    def end_visit_field(self, node):
        print('end field %s visit' % node)

And using it to visit a parsed query:

from graphql_parser import GraphQLParser

query = '{query{}}'
node = GraphQLParser.graphql_parse_string(query)
MyVisitor().visit_node(node)

See also examples folder.

Building from source checkout

Rebuild the generated cython files from the libgraphql AST (usually not needed)

• download submodules with git checkout --recursive

• build libgraphql library in folder ./libgraphqlparser (python2.7 required for building) (usually pushd libgraphqlparser && cmake . && make && popd works)

• generate source code with python ast/build_ast.py

• you can now switch to python 3

• install cython

• run:

  LDFLAGS="-L./libgraphqlparser" CFLAGS="-Ilibgraphqlparser/c -Ilibgraphqlparser" python setup.py build_ext
  

To create a wheel distribution:

• install wheel: pip install wheel
• create wheelhouse mkdir .wheelhouse
• build with pip wheel --wheel-dir=.wheelhouse .

Known issues

• Only (lightly) tested on python3
• Unicode string handling not yet complete (a mixture of bytes and strings all over)
• Exceptions in the visitor's class callbacks are ignored
• libgraphqlparser is dynamically linked but It would be better if it was linked statically

TODO

• build more wheel packages for linux 32 bit and other platforms