GraphQL Query Merger

GraphQL Query Merger is a utility library designed to merge multiple GraphQL queries into a single, cohesive query. This helps developers streamline their GraphQL requests by combining related operations efficiently, avoiding redundancy and improving maintainability.

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Table of Contents

• GraphQL Query Merger
  • Table of Contents
  • Features
  • Installation
  • Usage
    • Importing the Library
    • Combining Queries
      • Basic Query Combination
      • Combining Queries with Variables
      • Conditional Query Combination
  • Notes

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Features

• Merge GraphQL Queries: Seamlessly combine multiple queries into one.
• Variable Deduplication: Automatically handles conflicts by renaming variables.
• Supports Conditional Queries: Add queries dynamically based on runtime logic.
• Customizable Query Names: Optionally name the resulting query.

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Installation

To install the library, use npm or yarn:

npm install graphql-query-merger graphql

Note: graphql-query-merger has a peer dependency on graphql. Ensure that the graphql package is installed alongside it.

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Usage

Importing the Library

To use the library, import the necessary functions:

const { mergeQueries } = require('graphql-query-merger');
const { print } = require('graphql');
const { gql } = require('graphql-tag');

• mergeQueries(): Initializes a new query merger instance.
• push(query, variables?): Adds a query to the merger. Optionally accepts a variables object.
• print(): Converts the resulting query to a printable string format.

Combining Queries

Basic Query Combination

You can combine queries written as strings or gql-tagged templates.

const query_1 = /* GraphQL */ `
  {
    user {
      id
      name
    }
  }
`;

const query_2 = /* GraphQL */ gql`
  {
    post {
      id
      title
    }
  }
`;

const combined = mergeQueries().push(query_1).push(query_2);

console.log(print(combined.query));

Output:

{
  user {
    id
    name
  }
  post {
    id
    title
  }
}

Combining Queries with Variables

When combining queries that include variables, the library automatically renames conflicting variable names to maintain uniqueness.

const query_1 = /* GraphQL */ gql`
  query ($id: ID!) {
    user(id: $id) {
      id
      name
    }
  }
`;

const query_2 = /* GraphQL */ `
  query ($id: ID!) {
    post(id: $id) {
      id
      title
    }
  }
`;

const combined = mergeQueries().push(query_1, { id: 1 }).push(query_2, { id: 2 });

console.log(print(combined.query));
console.log(combined.variables);

Output:

query ($id_1: ID!, $id_2: ID!) {
  user(id: $id_1) {
    id
    name
  }
  post(id: $id_2) {
    id
    title
  }
}

Variables:

{
  "id_1": 1,
  "id_2": 2
}

• Automatic Variable Renaming: Conflicting variable names (id) are renamed (id_1, id_2).

Conditional Query Combination

You can dynamically add queries based on runtime conditions.

const combined = mergeQueries('optionalQueryName');

combined.push(
  /* GraphQL */ `
    query ($email: String!) {
      user(email: $email) {
        id
        name
      }
    }
  `,
  { email: '[email protected]' },
);

if (true) {
  combined.push(
    /* GraphQL */ `
      query ($id: ID!) {
        post(id: $id) {
          id
          title
          date
        }
      }
    `,
    { id: 10 },
  );
}

console.log(print(combined.query));
console.log(combined.variables);

Output:

query optionalQueryName($email_1: String!, $id_2: ID!) {
  user(email: $email_1) {
    id
    name
  }
  post(id: $id_2) {
    id
    title
    date
  }
}

Variables:

{
  "email_1": "[email protected]",
  "id_2": 10
}

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Notes

1. Variable Scope: The library renames variables in the combined query to ensure no conflicts occur between different queries.
2. Query Formats: Queries can be provided as:
   • String literals
   • gql-tagged templates (recommended for syntax highlighting and validation).
3. Error Handling: Ensure all variables required by the queries are provided when invoking push(). Missing variables will lead to runtime errors.