SchemaGen

Schema Gen is a simple CLI tool that generates Python GraphQL implementations(using Graphene) from a Graphql Schema file.

Installation

pip install schemagen

Usage

Here's the content of a sample input file(we will call it test.graphql)

typeUser {
id: ID!username: Stringfirst_name: Stringlast_name: Stringfull_name: Stringname: Stringname: String
}

Now let's use SchemaGen to generate python code from it.

As a CLI tool:

schemagen parse test.graphql -o test.py

As a Python Package:

fromschemagenimportSchemaGengen=SchemaGen(
input_file='test.graphql',
output_file='test.py'
)
# parse input filegen()

Output(test.py):

# This file was generated by CodegenToolfromgrapheneimport*classUser(ObjectType):
id=Field(ID, required=True)
username=Field(String)
first_name=Field(String)
last_name=Field(String)
full_name=Field(String)
name=Field(String)

Notes

Here are some things you should know about using SchemaGen:

• SchemaGen is not guaranteed to catch errors in your GraphQL schema file.

  SchemaGen will only catch a very small percentage of errors that might occur in defining a GraphQL schema. It is the developer's responsibility to ensure the GraphQL schema file is error-free.

• SchemaGen will not install the graphene package on your local machine however it will import it in the generated python file.

  You can easily install the package by running:

  pip install graphene

• GraphQL type declarations in your schema file must be ordered.

  Because of the way Python and SchemaGen works, you cannot use a GraphQL type before declaring it. For example, the following graphql schema definition would be invalid because we are using the Url scalar in our User type before declaring it:

  typeUser {
  id: ID!username: Stringavatar_url: Url
  }
  scalarUrl

  The correct version of the above code is:

  scalarUrltypeUser {
  id: ID!username: Stringavatar_url: Url
  }

• Using a GraphQL SDL keyword as an object field name in your schema will throw an error.

  For example, doing this:

  enumUserType {
   Example
  }
  typeUser{
  name: Stringtype: UserType
  }

  will throw an error.

  Do this instead:

  enumUserType {
   Example
  }
  typeUser{
  name: Stringuser_type: UserType
  }

I plan to fix the last two issues stated above in the future. Pull requests are welcome!