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Merged
andimarek merged 2 commits into from
Aug 24, 2026
Merged

Backport 25.1: Validation cleanup #4462

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5ef7f42
Make fragment cycle validation linear
andimarek Aug 18, 2026
6f0cb3a
Merge remote-tracking branch 'origin/25.x' into codex/backport-4441-t…
andimarek Aug 23, 2026
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91 changes: 49 additions & 42 deletions src/main/java/graphql/validation/rules/NoFragmentCycles.java
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Original file line number Diff line number Diff line change
@@ -1,10 +1,13 @@
package graphql.validation.rules;


import java.util.ArrayDeque;
import java.util.Collections;
import java.util.HashMap;
import java.util.Deque;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
Expand All @@ -26,11 +29,13 @@
@Internal
public class NoFragmentCycles extends AbstractRule {

private final Map<String, Set<String>> fragmentSpreads = new HashMap<>();
private final Map<String, Set<String>> fragmentSpreads = new LinkedHashMap<>();
private final Set<String> fragmentsWithCycleErrors = new HashSet<>();

public NoFragmentCycles(ValidationContext validationContext, ValidationErrorCollector validationErrorCollector) {
super(validationContext, validationErrorCollector);
prepareFragmentMap();
findFragmentCycles();
}

private void prepareFragmentMap() {
Expand All @@ -44,7 +49,7 @@ private void prepareFragmentMap() {
}

private Set<String> gatherSpreads(FragmentDefinition fragmentDefinition) {
final Set<String> fragmentSpreads = new HashSet<>();
final Set<String> fragmentSpreads = new LinkedHashSet<>();
DocumentVisitor visitor = new DocumentVisitor() {
@Override
public void enter(Node node, List<Node> path) {
Expand All @@ -65,54 +70,56 @@ public void leave(Node node, List<Node> path) {

@Override
public void checkFragmentDefinition(FragmentDefinition fragmentDefinition) {
LinkedList<String> path = new LinkedList<>();
path.add(0, fragmentDefinition.getName());
Map<String, Set<String>> transitiveSpreads = buildTransitiveSpreads(path, new HashMap<>());

for (Map.Entry<String, Set<String>> entry : transitiveSpreads.entrySet()) {
if (entry.getValue().contains(entry.getKey())) {
String message = i18n(FragmentCycle, "NoFragmentCycles.cyclesNotAllowed");
addError(ValidationErrorType.FragmentCycle, Collections.singletonList(fragmentDefinition), message);
}
if (!fragmentsWithCycleErrors.contains(fragmentDefinition.getName())) {
return;
}
String message = i18n(FragmentCycle, "NoFragmentCycles.cyclesNotAllowed");
addError(ValidationErrorType.FragmentCycle, Collections.singletonList(fragmentDefinition), message);
}

private Map<String, Set<String>> buildTransitiveSpreads(LinkedList<String> path, Map<String, Set<String>> transitiveSpreads) {
String name = path.peekFirst();

if (transitiveSpreads.containsKey(name)) {
return transitiveSpreads;
}

Set<String> spreads = fragmentSpreads.get(name);

// spreads may be null when there is no corresponding FragmentDefinition for this spread.
// This will be handled by KnownFragmentNames
if (spreads == null || spreads.isEmpty()) {
return transitiveSpreads;
private void findFragmentCycles() {
Set<String> visitedFragments = new HashSet<>();
for (Map.Entry<String, Set<String>> entry : fragmentSpreads.entrySet()) {
if (!visitedFragments.add(entry.getKey())) {
continue;
}
findFragmentCycles(entry.getKey(), entry.getValue(), visitedFragments);
}
}

// Add the current spreads to the transitive spreads of each ancestor in the traversal path
for (String ancestor : path) {
Set<String> ancestorSpreads = transitiveSpreads.get(ancestor);
if (ancestorSpreads == null) {
ancestorSpreads = new HashSet<>();
private void findFragmentCycles(String firstFragment, Set<String> firstSpreads, Set<String> visitedFragments) {
Set<String> visitingFragments = new HashSet<>();
Deque<String> fragmentStack = new ArrayDeque<>();
Deque<Iterator<String>> spreadIteratorStack = new ArrayDeque<>();
visitingFragments.add(firstFragment);
fragmentStack.push(firstFragment);
spreadIteratorStack.push(firstSpreads.iterator());

while (!fragmentStack.isEmpty()) {
Iterator<String> spreadIterator = spreadIteratorStack.getFirst();
if (!spreadIterator.hasNext()) {
visitingFragments.remove(fragmentStack.pop());
spreadIteratorStack.pop();
continue;
}
ancestorSpreads.addAll(spreads);
transitiveSpreads.put(ancestor, ancestorSpreads);
}

for (String child : spreads) {
// don't recurse infinitely, expect the recursion check to happen in checkFragmentDefinition
if (path.contains(child) || transitiveSpreads.containsKey(child)) {
String childFragment = spreadIterator.next();
Set<String> childSpreads = fragmentSpreads.get(childFragment);
if (childSpreads == null) {
continue;
}
if (visitingFragments.contains(childFragment)) {
fragmentsWithCycleErrors.add(childFragment);
fragmentsWithCycleErrors.add(fragmentStack.getFirst());
continue;
}
if (!visitedFragments.add(childFragment)) {
continue;
}

// descend into each spread in the current fragment
LinkedList<String> childPath = new LinkedList<>(path);
childPath.add(0, child);
buildTransitiveSpreads(childPath, transitiveSpreads);
visitingFragments.add(childFragment);
fragmentStack.push(childFragment);
spreadIteratorStack.push(childSpreads.iterator());
}
return transitiveSpreads;
}
}
28 changes: 28 additions & 0 deletions src/test/groovy/graphql/validation/rules/NoFragmentCyclesTest.groovy
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Original file line number Diff line number Diff line change
Expand Up @@ -238,4 +238,32 @@ class NoFragmentCyclesTest extends Specification {
errorCollector.containsValidationError(ValidationErrorType.FragmentCycle)
errorCollector.getErrors()[0].message == "Validation error (FragmentCycle@[MyFrag]) : Fragment cycles not allowed"
}

def "long acyclic fragment chains are valid"() {
when:
traverse(fragmentChain(1_000, false))

then:
errorCollector.getErrors().isEmpty()
}

def "cycles at the end of long fragment chains are detected"() {
when:
traverse(fragmentChain(1_000, true))

then:
errorCollector.containsValidationError(ValidationErrorType.FragmentCycle)
}

private static String fragmentChain(int fragmentCount, boolean cycle) {
(0..<fragmentCount).collect { index ->
String selection = "name"
if (index < fragmentCount - 1) {
selection = "...F${index + 1}"
} else if (cycle) {
selection = "...F${fragmentCount.intdiv(2)}"
}
"fragment F${index} on Dog { ${selection} }"
}.join("\n")
}
}
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