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package validator
import (
"strconv"
"strings"
"github.com/vektah/gqlparser/v2/ast"
//nolint:revive // Validator rules each use dot imports for convenience.
. "github.com/vektah/gqlparser/v2/validator"
)
func init() {
AddRule("SingleFieldSubscriptions", func(observers *Events, addError AddErrFunc) {
observers.OnOperation(func(walker *Walker, operation *ast.OperationDefinition) {
if walker.Schema.Subscription == nil || operation.Operation != ast.Subscription {
return
}
fields := retrieveTopFieldNames(operation.SelectionSet)
name := "Anonymous Subscription"
if operation.Name != "" {
name = `Subscription ` + strconv.Quote(operation.Name)
}
if len(fields) > 1 {
addError(
Message(`%s must select only one top level field.`, name),
At(fields[1].position),
)
}
for _, field := range fields {
if strings.HasPrefix(field.name, "__") {
addError(
Message(`%s must not select an introspection top level field.`, name),
At(field.position),
)
}
}
})
})
}
type topField struct {
name string
position *ast.Position
}
func retrieveTopFieldNames(selectionSet ast.SelectionSet) []*topField {
fields := []*topField{}
inFragmentRecursive := map[string]bool{}
var walk func(selectionSet ast.SelectionSet)
walk = func(selectionSet ast.SelectionSet) {
for _, selection := range selectionSet {
switch selection := selection.(type) {
case *ast.Field:
fields = append(fields, &topField{
name: selection.Name,
position: selection.GetPosition(),
})
case *ast.InlineFragment:
walk(selection.SelectionSet)
case *ast.FragmentSpread:
if selection.Definition == nil {
return
}
fragment := selection.Definition.Name
if !inFragmentRecursive[fragment] {
inFragmentRecursive[fragment] = true
walk(selection.Definition.SelectionSet)
}
}
}
}
walk(selectionSet)
seen := make(map[string]bool, len(fields))
uniquedFields := make([]*topField, 0, len(fields))
for _, field := range fields {
if !seen[field.name] {
uniquedFields = append(uniquedFields, field)
}
seen[field.name] = true
}
return uniquedFields
}
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