GraphQL Inspector - Validate

GraphQL Inspector - Validate

Expert knowledge of GraphQL Inspector's validate command for checking operations and documents against a schema with configurable rules.

Overview

The validate command checks GraphQL operations (queries, mutations, subscriptions) and fragments against a schema. It catches errors like undefined fields, wrong argument types, and invalid fragment spreads before runtime.

Core Commands

Basic Validation

# Validate operations against schema
npx @graphql-inspector/​cli validate './​src/​**/​*.graphql' './​schema.graphql'

# Validate operations from TypeScript files
npx @graphql-inspector/​cli validate './​src/​**/​*.tsx' './​schema.graphql'

# Validate with glob patterns
npx @graphql-inspector/​cli validate './​**/​*.{graphql,gql}' './​schema.graphql'

Federation Support

# Apollo Federation V1
npx @graphql-inspector/​cli validate './​operations/​**/​*.graphql' './​schema.graphql' \
  --federation

# Apollo Federation V2
npx @graphql-inspector/​cli validate './​operations/​**/​*.graphql' './​schema.graphql' \
  --federationV2

# AWS AppSync directives
npx @graphql-inspector/​cli validate './​operations/​**/​*.graphql' './​schema.graphql' \
  --aws

Validation Rules

Depth Limiting

Prevent deeply nested queries that could cause performance issues:

# Fail if query depth exceeds 10
npx @graphql-inspector/​cli validate './​src/​**/​*.graphql' './​schema.graphql' \
  --maxDepth 10

Example violation:

# Depth of 8 - might exceed limit
query DeepQuery {
  user {                     # 1
    posts {                  # 2
      author {               # 3
        followers {          # 4
          posts {            # 5
            comments {       # 6
              author {       # 7
                name         # 8
              }
            }
          }
        }
      }
    }
  }
}

Alias Count

Limit alias usage to prevent response explosion:

# Max 5 aliases per operation
npx @graphql-inspector/​cli validate './​src/​**/​*.graphql' './​schema.graphql' \
  --maxAliasCount 5

Example violation:

# 6 aliases - exceeds limit of 5
query TooManyAliases {
  user1: user(id: "1") { name }
  user2: user(id: "2") { name }
  user3: user(id: "3") { name }
  user4: user(id: "4") { name }
  user5: user(id: "5") { name }
  user6: user(id: "6") { name }  # Exceeds limit
}

Directive Count

Limit directives to prevent abuse:

# Max 10 directives per operation
npx @graphql-inspector/​cli validate './​src/​**/​*.graphql' './​schema.graphql' \
  --maxDirectiveCount 10

Token Count

Limit query complexity by token count:

# Max 1000 tokens per operation
npx @graphql-inspector/​cli validate './​src/​**/​*.graphql' './​schema.graphql' \
  --maxTokenCount 1000

Complexity Score

Calculate and limit query complexity:

# Max complexity score of 100
npx @graphql-inspector/​cli validate './​src/​**/​*.graphql' './​schema.graphql' \
  --maxComplexityScore 100

Configuration File

Create .graphql-inspector.yaml:

validate:
  schema: './​schema.graphql'
  documents: './​src/​**/​*.graphql'

  # Validation limits
  maxDepth: 10
  maxAliasCount: 5
  maxDirectiveCount: 10
  maxTokenCount: 1000
  maxComplexityScore: 100

  # Federation support
  federation: false
  federationV2: false
  aws: false

Common Validation Errors

Unknown Field

Error: Cannot query field "unknownField" on type "User".

Fix: Check field name spelling or add field to schema.

Wrong Argument Type

Error: Argument "id" has invalid value "123".
Expected type "ID!", found "123" (String).

Fix: Use correct type for argument.

Missing Required Argument

Error: Field "user" argument "id" of type "ID!" is required.

Fix: Provide required argument.

Invalid Fragment Spread

Error: Fragment "UserFields" cannot be spread here as objects of
type "Post" can never be of type "User".

Fix: Ensure fragment type matches spread location.

Unused Fragment

Warning: Fragment "UnusedFragment" is never used.

Fix: Remove or use the fragment.

CI/​CD Integration

GitHub Actions

name: Validate Operations
on:
  pull_request:
    paths:
      - 'src/​**/​*.graphql'
      - 'src/​**/​*.tsx'
      - 'schema.graphql'

jobs:
  validate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/​checkout@v4

      - name: Install Inspector
        run: npm install -g @graphql-inspector/​cli

      - name: Validate operations
        run: |
          graphql-inspector validate \
            'src/​**/​*.graphql' \
            schema.graphql \
            --maxDepth 10 \
            --maxAliasCount 5

Pre-commit Hook

{
  "husky": {
    "hooks": {
      "pre-commit": "graphql-inspector validate 'src/​**/​*.graphql' schema.graphql"
    }
  }
}

Extracting Operations from Code

GraphQL Inspector can extract operations from various file types:

TypeScript/​JavaScript

// Operations in template literals are detected
const GET_USER = gql`
  query GetUser($id: ID!) {
    user(id: $id) {
      name
      email
    }
  }
`;

React with GraphQL

// Tagged template literals in React files
import { gql } from '@apollo/​client';

const USER_QUERY = gql`
  query UserQuery {
    currentUser {
      id
      name
    }
  }
`;

Best Practices

1. Validate in CI - Run validation on every PR affecting GraphQL files
2. Set reasonable limits - Start with permissive limits, tighten over time
3. Validate against production schema - Ensure operations work in production
4. Extract operations from code - Validate all operations, not just .graphql files
5. Use Federation flags - Enable if using Apollo Federation
6. Fail on warnings - Treat unused fragments as errors in CI
7. Version your schema - Validate against specific schema versions
8. Document limits - Explain why limits exist to developers

Common Patterns

Multi-Schema Validation

For monorepos with multiple schemas:

# Validate against specific service schema
npx @graphql-inspector/​cli validate \
  './​packages/​app/​src/​**/​*.graphql' \
  './​packages/​api/​schema.graphql'

# Validate against federated supergraph
npx @graphql-inspector/​cli validate \
  './​packages/​web/​src/​**/​*.graphql' \
  './​supergraph.graphql' \
  --federationV2

Incremental Adoption

Start permissive, add stricter rules over time:

# Phase 1: Basic validation only
validate:
  schema: './​schema.graphql'
  documents: './​src/​**/​*.graphql'

# Phase 2: Add depth limiting
validate:
  schema: './​schema.graphql'
  documents: './​src/​**/​*.graphql'
  maxDepth: 15

# Phase 3: Add complexity limits
validate:
  schema: './​schema.graphql'
  documents: './​src/​**/​*.graphql'
  maxDepth: 10
  maxAliasCount: 10
  maxComplexityScore: 200

Troubleshooting

"Schema file not found"

• Verify schema path is correct
• Check glob pattern matches schema location
• Use absolute path if relative fails

"No documents found"

• Check glob pattern matches operation files
• Verify file extensions are correct
• Ensure files contain GraphQL operations

"Unknown directive"

• Add --federation or --federationV2 for Federation directives
• Add --aws for AppSync directives
• Check custom directives are defined in schema

Operations not detected in code

• Ensure using tagged template literal (gql\...``)
• Check file extension is included in glob
• Verify GraphQL Inspector can parse the file type

When to Use This Skill

• Setting up operation validation in CI/​CD
• Enforcing query complexity limits
• Validating operations before deployment
• Catching schema-operation mismatches early
• Preventing deeply nested queries
• Auditing existing operations for compliance