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package validator
import (
"fmt"
"strings"
"github.com/vektah/gqlparser/ast"
. "github.com/vektah/gqlparser/validator"
)
func init() {
AddRule("NoFragmentCycles", func(observers *Events, addError AddErrFunc) {
visitedFrags := make(map[string]bool)
observers.OnFragment(func(walker *Walker, fragment *ast.FragmentDefinition) {
var spreadPath []*ast.FragmentSpread
spreadPathIndexByName := make(map[string]int)
var recursive func(fragment *ast.FragmentDefinition)
recursive = func(fragment *ast.FragmentDefinition) {
if visitedFrags[fragment.Name] {
return
}
visitedFrags[fragment.Name] = true
spreadNodes := getFragmentSpreads(fragment.SelectionSet)
if len(spreadNodes) == 0 {
return
}
spreadPathIndexByName[fragment.Name] = len(spreadPath)
for _, spreadNode := range spreadNodes {
spreadName := spreadNode.Name
cycleIndex, ok := spreadPathIndexByName[spreadName]
spreadPath = append(spreadPath, spreadNode)
if !ok {
spreadFragment := walker.Document.Fragments.ForName(spreadName)
if spreadFragment != nil {
recursive(spreadFragment)
}
} else {
cyclePath := spreadPath[cycleIndex : len(spreadPath)-1]
var fragmentNames []string
for _, fs := range cyclePath {
fragmentNames = append(fragmentNames, fs.Name)
}
var via string
if len(fragmentNames) != 0 {
via = fmt.Sprintf(" via %s", strings.Join(fragmentNames, ", "))
}
addError(
Message(`Cannot spread fragment "%s" within itself%s.`, spreadName, via),
At(spreadNode.Position),
)
}
spreadPath = spreadPath[:len(spreadPath)-1]
}
delete(spreadPathIndexByName, fragment.Name)
}
recursive(fragment)
})
})
}
func getFragmentSpreads(node ast.SelectionSet) []*ast.FragmentSpread {
var spreads []*ast.FragmentSpread
setsToVisit := []ast.SelectionSet{node}
for len(setsToVisit) != 0 {
set := setsToVisit[len(setsToVisit)-1]
setsToVisit = setsToVisit[:len(setsToVisit)-1]
for _, selection := range set {
switch selection := selection.(type) {
case *ast.FragmentSpread:
spreads = append(spreads, selection)
case *ast.Field:
setsToVisit = append(setsToVisit, selection.SelectionSet)
case *ast.InlineFragment:
setsToVisit = append(setsToVisit, selection.SelectionSet)
}
}
}
return spreads
}
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