Package Exports

graphql-anywhere
graphql-anywhere/lib/src/getFromAST

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Readme

graphql-anywhere

Run a GraphQL query anywhere, without a GraphQL server or a schema. Just pass in one resolver. Use it together with graphql-tag.

npm install graphql-anywhere graphql-tag

I think there are a lot of potentially exciting use cases for a completely standalone and schema-less GraphQL execution engine. We use it in Apollo Client to read data from a Redux store with GraphQL.

Let's come up with some more ideas - below are some use cases to get you started!

API

import graphql from 'graphql-anywhere'

graphql(resolver, document, rootValue?, context?, variables?)

resolver: A single resolver, called for every field on the query.
- Signature is: (fieldName, rootValue, args, context) => any
document: A GraphQL document, as generated by the template literal from graphql-tag
rootValue: The root value passed to the resolver when executing the root fields
context: A context object passed to the resolver for every field
variables: A dictionary of variables for the query

Example: Filter a nested object

import gql from 'graphql-tag';
import graphql from 'graphql-anywhere';

// I don't need all this stuff!
const gitHubAPIResponse = {
  "url": "https://api.github.com/repos/octocat/Hello-World/issues/1347",
  "title": "Found a bug",
  "body": "I'm having a problem with this.",
  "user": {
    "login": "octocat",
    "avatar_url": "https://github.com/images/error/octocat_happy.gif",
    "url": "https://api.github.com/users/octocat",
  },
  "labels": [
    {
      "url": "https://api.github.com/repos/octocat/Hello-World/labels/bug",
      "name": "bug",
      "color": "f29513"
    }
  ],
};

// Write a query that gets just the fields we want
const query = gql`
  {
    title
    user {
      login
    }
    labels {
      name
    }
  }
`;

// Define a resolver that just returns a property
const resolver = (fieldName, root) => root[fieldName];

// Filter the data!
const result = graphql(
  resolver,
  query,
  gitHubAPIResponse
);

assert.deepEqual(result, {
  "title": "Found a bug",
  "user": {
    "login": "octocat",
  },
  "labels": [
    {
      "name": "bug",
    }
  ],
});

Example: Generate mock data

// Write a query where the fields are types, but we alias them
const query = gql`
  {
    author {
      name: string
      age: int
      address {
        state: string
      }
    }
  }
`;

// Define a resolver that uses the field name to determine the type
// Note that we get the actual name, not the alias, but the alias
// is used to determine the location in the response
const resolver = (fieldName) => ({
  string: 'This is a string',
  int: 5,
}[fieldName]);

// Generate the object!
const result = graphql(
  resolver,
  query
);

assert.deepEqual(result, {
  author: {
    name: 'This is a string',
    age: 5,
    address: {
      state: 'This is a string',
    },
  },
});

Example: Read from a Redux store generated with Normalizr

const data = {
  result: [1, 2],
  entities: {
    articles: {
      1: { id: 1, title: 'Some Article', author: 1 },
      2: { id: 2, title: 'Other Article', author: 1 },
    },
    users: {
      1: { id: 1, name: 'Dan' },
    },
  },
};

const query = gql`
  {
    result {
      title
      author {
        name
      }
    }
  }
`;

const schema = {
  articles: {
    author: 'users',
  },
};

// This resolver is a bit more complex than others, since it has to
// correctly handle the root object, values by ID, and scalar leafs.
const resolver = (fieldName, rootValue, args, context): any => {
  if (!rootValue) {
    return context.result.map((id) => assign({}, context.entities.articles[id], {
      __typename: 'articles',
    }));
  }

  const typename = rootValue.__typename;
  // If this field is a reference according to the schema
  if (typename && schema[typename] && schema[typename][fieldName]) {
    // Get the target type, and get it from entities by ID
    const targetType: string = schema[typename][fieldName];
    return assign({}, context.entities[targetType][rootValue[fieldName]], {
      __typename: targetType,
    });
  }

  // This field is just a scalar
  return rootValue[fieldName];
};

const result = graphql(
  resolver,
  query,
  null,
  data // pass data as context since we have to access it all the time
);

// This is the non-normalized data, with only the fields we asked for in our query!
assert.deepEqual(result, {
  result: [
    {
      title: 'Some Article',
      author: {
        name: 'Dan',
      },
    },
    {
      title: 'Other Article',
      author: {
        name: 'Dan',
      },
    },
  ],
});

What does this support?

Every GraphQL syntax feature I can think of is supported, as far as I know, including aliases, arguments, variables, inline fragments, named fragments, and skip/include directives.

Known limitations:

The execution engine is synchronous, so you probably shouldn't use this to query your API. Please submit a PR to add promise functionality, and ideally batching support, like graphql-js has! Wouldn't it be cool if you could use this to dynamically query a REST API via GraphQL?