feat: new rule for excessive fields

[theodesp]

Description

This PR introduces a new GraphQL debug rule: ExcessiveFields.

The rule analyzes GraphQL queries to detect over-fetching, i.e., selecting an excessive number of fields for a single object type.
It uses the GraphQL schema to traverse queries and count fields per type. If any type exceeds the configurable threshold, the rule is triggered.

Key features:

• Detects over-fetching across nested fields.
• Configurable threshold via WordPress filter: graphql_debug_rule_excessive_fields_threshold
• Full doc comments for maintainability.
• Returns structured output indicating whether the rule is triggered and a descriptive message.

Related Issue

Dependant PRs

• None

Type of Change

• ✅ Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactoring (no functional changes)
• 📄 Example update (no functional changes)
• 📝 Documentation update
• 🔍 Performance improvement
• 🧪 Test update

How Has This Been Tested?

• Queries with fewer fields than the threshold correctly return "triggered": false.
• Queries exceeding the threshold correctly return "triggered": true.
• Nested fields are counted properly using the schema.
• Threshold can be modified using the WordPress filter.

Example filter usage:

// Set custom threshold to 20 fields
add_filter( 'graphql_debug_rule_excessive_fields_threshold', function( $default, $query, $variables, $schema ) {
    return 20;
}, 10, 4 )

Example Queries

Query that triggers the rule

query InefficientQuery {
  posts(first: 1) {
    nodes {
      id
      title
      slug
      uri
      status
      date
      modified
      commentCount
      commentStatus
      pingStatus
      password
      link
      featuredImage {
        node {
          sourceUrl
          altText
          caption
        }
      }
      author {
        node {
          name
          email
          firstName
          lastName
          registeredDate
          description
          nickname
        }
      }
      content
      excerpt
    }
  }
}

Expected output:

{
  "excessiveFieldsRule": {
    "triggered": true,
    "message": "Over-fetching detected: Type \"Post\" selects 16 fields, exceeding the threshold of 15."
  }
}

Query that does NOT trigger the rule

query EfficientQuery {
  posts(first: 1) {
    nodes {
      id
      title
      slug
      content
    }
  }
}

Expected output:

{
  "excessiveFieldsRule": {
    "triggered": false,
    "message": "No excessive fields detected."
  }
}

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[github-actions]

ℹ️ Download the latest wpgraphql-debug-extensions plugin zip from this PR
(See the 'Artifacts' section at the bottom)

[colinmurphy]

15 fields seems a sensible number to me. LGTM 🚀 🚀 🚀