complexity.go

Documentation: github.com/99designs/gqlgen/graphql/handler/extension

     1  package extension
     2  
     3  import (
     4  	"context"
     5  	"fmt"
     6  
     7  	"github.com/vektah/gqlparser/v2/gqlerror"
     8  
     9  	"github.com/99designs/gqlgen/complexity"
    10  	"github.com/99designs/gqlgen/graphql"
    11  	"github.com/99designs/gqlgen/graphql/errcode"
    12  )
    13  
    14  const errComplexityLimit = "COMPLEXITY_LIMIT_EXCEEDED"
    15  
    16  // ComplexityLimit allows you to define a limit on query complexity
    17  //
    18  // If a query is submitted that exceeds the limit, a 422 status code will be returned.
    19  type ComplexityLimit struct {
    20  	Func func(ctx context.Context, rc *graphql.OperationContext) int
    21  
    22  	es graphql.ExecutableSchema
    23  }
    24  
    25  var _ interface {
    26  	graphql.OperationContextMutator
    27  	graphql.HandlerExtension
    28  } = &ComplexityLimit{}
    29  
    30  const complexityExtension = "ComplexityLimit"
    31  
    32  type ComplexityStats struct {
    33  	// The calculated complexity for this request
    34  	Complexity int
    35  
    36  	// The complexity limit for this request returned by the extension func
    37  	ComplexityLimit int
    38  }
    39  
    40  // FixedComplexityLimit sets a complexity limit that does not change
    41  func FixedComplexityLimit(limit int) *ComplexityLimit {
    42  	return &ComplexityLimit{
    43  		Func: func(ctx context.Context, rc *graphql.OperationContext) int {
    44  			return limit
    45  		},
    46  	}
    47  }
    48  
    49  func (c ComplexityLimit) ExtensionName() string {
    50  	return complexityExtension
    51  }
    52  
    53  func (c *ComplexityLimit) Validate(schema graphql.ExecutableSchema) error {
    54  	if c.Func == nil {
    55  		return fmt.Errorf("ComplexityLimit func can not be nil")
    56  	}
    57  	c.es = schema
    58  	return nil
    59  }
    60  
    61  func (c ComplexityLimit) MutateOperationContext(ctx context.Context, rc *graphql.OperationContext) *gqlerror.Error {
    62  	op := rc.Doc.Operations.ForName(rc.OperationName)
    63  	complexityCalcs := complexity.Calculate(c.es, op, rc.Variables)
    64  
    65  	limit := c.Func(ctx, rc)
    66  
    67  	rc.Stats.SetExtension(complexityExtension, &ComplexityStats{
    68  		Complexity:      complexityCalcs,
    69  		ComplexityLimit: limit,
    70  	})
    71  
    72  	if complexityCalcs > limit {
    73  		err := gqlerror.Errorf("operation has complexity %d, which exceeds the limit of %d", complexityCalcs, limit)
    74  		errcode.Set(err, errComplexityLimit)
    75  		return err
    76  	}
    77  
    78  	return nil
    79  }
    80  
    81  func GetComplexityStats(ctx context.Context) *ComplexityStats {
    82  	rc := graphql.GetOperationContext(ctx)
    83  	if rc == nil {
    84  		return nil
    85  	}
    86  
    87  	s, _ := rc.Stats.GetExtension(complexityExtension).(*ComplexityStats)
    88  	return s
    89  }
    90
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