graphql.util.CyclicSchemaAnalyzer Maven / Gradle / Ivy
package graphql.util;
import graphql.Assert;
import graphql.ExperimentalApi;
import graphql.introspection.Introspection;
import graphql.schema.GraphQLSchema;
import graphql.schema.diffing.Edge;
import graphql.schema.diffing.SchemaGraph;
import graphql.schema.diffing.SchemaGraphFactory;
import graphql.schema.diffing.Vertex;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;
/**
* Finds all cycles in a GraphQL Schema.
* Cycles caused by built-in introspection types are filtered out.
*/
@ExperimentalApi
public class CyclicSchemaAnalyzer {
public static class SchemaCycle {
private final List cycle;
public SchemaCycle(List cycle) {
this.cycle = cycle;
}
public int size() {
return cycle.size();
}
public List getCycle() {
return cycle;
}
@Override
public String toString() {
return cycle.toString();
}
}
public static List findCycles(GraphQLSchema schema) {
return findCycles(schema, true);
}
public static List findCycles(GraphQLSchema schema, boolean filterOutIntrospectionCycles) {
FindCyclesImpl findCyclesImpl = new FindCyclesImpl(schema);
findCyclesImpl.findAllSimpleCyclesImpl();
List> vertexCycles = findCyclesImpl.foundCycles;
if (filterOutIntrospectionCycles) {
vertexCycles = vertexCycles.stream().filter(vertices -> {
for (Vertex vertex : vertices) {
if (Introspection.isIntrospectionTypes(vertex.getName())) {
return false;
}
}
return true;
}).collect(Collectors.toList());
}
List result = new ArrayList<>();
for (List vertexCycle : vertexCycles) {
List stringCycle = new ArrayList<>();
for (Vertex vertex : vertexCycle) {
if (vertex.isOfType(SchemaGraph.OBJECT) || vertex.isOfType(SchemaGraph.INTERFACE) || vertex.isOfType(SchemaGraph.UNION)) {
stringCycle.add(vertex.getName());
} else if (vertex.isOfType(SchemaGraph.FIELD)) {
String fieldsContainerName = findCyclesImpl.graph.getFieldsContainerForField(vertex).getName();
stringCycle.add(fieldsContainerName + "." + vertex.getName());
} else if (vertex.isOfType(SchemaGraph.INPUT_OBJECT)) {
stringCycle.add(vertex.getName());
} else if (vertex.isOfType(SchemaGraph.INPUT_FIELD)) {
String inputFieldsContainerName = findCyclesImpl.graph.getFieldsContainerForField(vertex).getName();
stringCycle.add(inputFieldsContainerName + "." + vertex.getName());
} else {
Assert.assertShouldNeverHappen("unexpected vertex in cycle found: " + vertex);
}
}
result.add(new SchemaCycle(stringCycle));
}
return result;
}
private static class GraphAndIndex {
final SchemaGraph graph;
final int index;
public GraphAndIndex(SchemaGraph graph, int index) {
this.graph = graph;
this.index = index;
}
}
/**
* This code was originally taken from https://github.com/jgrapht/jgrapht/blob/master/jgrapht-core/src/main/java/org/jgrapht/alg/cycle/JohnsonSimpleCycles.java
* * (C) Copyright 2013-2023, by Nikolay Ognyanov and Contributors.
* *
* * JGraphT : a free Java graph-theory library
* *
* * See the CONTRIBUTORS.md file distributed with this work for additional
* * information regarding copyright ownership.
* *
* * This program and the accompanying materials are made available under the
* * terms of the Eclipse Public License 2.0 which is available at
* * http://www.eclipse.org/legal/epl-2.0, or the
* * GNU Lesser General Public License v2.1 or later
* * which is available at
* * http://www.gnu.org/licenses/old-licenses/lgpl-2.1-standalone.html.
* *
* * SPDX-License-Identifier: EPL-2.0 OR LGPL-2.1-or-later
*/
private static class FindCyclesImpl {
private final GraphQLSchema schema;
private final SchemaGraph graph;
// The main state of the algorithm.
private Vertex[] iToV = null;
private Map vToI = null;
private Set blocked = null;
private Map> bSets = null;
private ArrayDeque stack = null;
// The state of the embedded Tarjan SCC algorithm.
private List> foundSCCs = null;
private int index = 0;
private Map vIndex = null;
private Map vLowlink = null;
private ArrayDeque path = null;
private Set pathSet = null;
private List> foundCycles = new ArrayList<>();
public FindCyclesImpl(GraphQLSchema schema) {
this.schema = schema;
SchemaGraphFactory schemaGraphFactory = new SchemaGraphFactory();
this.graph = schemaGraphFactory.createGraph(schema);
iToV = (Vertex[]) graph.getVertices().toArray(new Vertex[0]);
vToI = new LinkedHashMap<>();
blocked = new LinkedHashSet<>();
bSets = new LinkedHashMap<>();
stack = new ArrayDeque<>();
for (int i = 0; i < iToV.length; i++) {
vToI.put(iToV[i], i);
}
}
public List> findAllSimpleCyclesImpl() {
int startIndex = 0;
int size = graph.getVertices().size();
while (startIndex < size) {
GraphAndIndex minSCCGResult = findMinSCSG(startIndex);
if (minSCCGResult != null) {
startIndex = minSCCGResult.index;
SchemaGraph scg = minSCCGResult.graph;
Vertex startV = toV(startIndex);
for (Edge e : scg.getAdjacentEdges(startV)) {
Vertex v = e.getTo();
blocked.remove(v);
getBSet(v).clear();
}
findCyclesInSCG(startIndex, startIndex, scg);
startIndex++;
} else {
break;
}
}
return this.foundCycles;
}
private GraphAndIndex findMinSCSG(int startIndex) {
/*
* Per Johnson : "adjacency structure of strong component $K$ with least vertex in subgraph
* of $G$ induced by $(s, s + 1, n)$". Or in contemporary terms: the strongly connected
* component of the subgraph induced by $(v_1, \dotso ,v_n)$ which contains the minimum
* (among those SCCs) vertex index. We return that index together with the graph.
*/
initMinSCGState();
List> foundSCCs = findSCCS(startIndex);
// find the SCC with the minimum index
int minIndexFound = Integer.MAX_VALUE;
Set minSCC = null;
for (Set scc : foundSCCs) {
for (Vertex v : scc) {
int t = toI(v);
if (t < minIndexFound) {
minIndexFound = t;
minSCC = scc;
}
}
}
if (minSCC == null) {
return null;
}
// build a graph for the SCC found
SchemaGraph resultGraph = new SchemaGraph();
for (Vertex v : minSCC) {
resultGraph.addVertex(v);
}
for (Vertex v : minSCC) {
for (Vertex w : minSCC) {
Edge edge = graph.getEdge(v, w);
if (edge != null) {
resultGraph.addEdge(edge);
}
}
}
GraphAndIndex graphAndIndex = new GraphAndIndex(resultGraph, minIndexFound);
clearMinSCCState();
return graphAndIndex;
}
private List> findSCCS(int startIndex) {
// Find SCCs in the subgraph induced
// by vertices startIndex and beyond.
// A call to StrongConnectivityAlgorithm
// would be too expensive because of the
// need to materialize the subgraph.
// So - do a local search by the Tarjan's
// algorithm and pretend that vertices
// with an index smaller than startIndex
// do not exist.
for (Vertex v : graph.getVertices()) {
int vI = toI(v);
if (vI < startIndex) {
continue;
}
if (!vIndex.containsKey(v)) {
getSCCs(startIndex, vI);
}
}
List> result = foundSCCs;
foundSCCs = null;
return result;
}
private void getSCCs(int startIndex, int vertexIndex) {
Vertex vertex = toV(vertexIndex);
vIndex.put(vertex, index);
vLowlink.put(vertex, index);
index++;
path.push(vertex);
pathSet.add(vertex);
List edges = graph.getAdjacentEdges(vertex);
for (Edge e : edges) {
Vertex successor = e.getTo();
int successorIndex = toI(successor);
if (successorIndex < startIndex) {
continue;
}
if (!vIndex.containsKey(successor)) {
getSCCs(startIndex, successorIndex);
vLowlink.put(vertex, Math.min(vLowlink.get(vertex), vLowlink.get(successor)));
} else if (pathSet.contains(successor)) {
vLowlink.put(vertex, Math.min(vLowlink.get(vertex), vIndex.get(successor)));
}
}
if (vLowlink.get(vertex).equals(vIndex.get(vertex))) {
Set result = new LinkedHashSet<>();
Vertex temp;
do {
temp = path.pop();
pathSet.remove(temp);
result.add(temp);
} while (!vertex.equals(temp));
if (result.size() == 1) {
Vertex v = result.iterator().next();
if (graph.containsEdge(vertex, v)) {
foundSCCs.add(result);
}
} else {
foundSCCs.add(result);
}
}
}
private boolean findCyclesInSCG(int startIndex, int vertexIndex, SchemaGraph scg) {
/*
* Find cycles in a strongly connected graph per Johnson.
*/
boolean foundCycle = false;
Vertex vertex = toV(vertexIndex);
stack.push(vertex);
blocked.add(vertex);
for (Edge e : scg.getAdjacentEdges(vertex)) {
Vertex successor = e.getTo();
int successorIndex = toI(successor);
if (successorIndex == startIndex) {
List cycle = new ArrayList<>(stack.size());
stack.descendingIterator().forEachRemaining(cycle::add);
this.foundCycles.add(cycle);
foundCycle = true;
} else if (!blocked.contains(successor)) {
boolean gotCycle = findCyclesInSCG(startIndex, successorIndex, scg);
foundCycle = foundCycle || gotCycle;
}
}
if (foundCycle) {
unblock(vertex);
} else {
for (Edge ew : scg.getAdjacentEdges(vertex)) {
Vertex w = ew.getTo();
Set bSet = getBSet(w);
bSet.add(vertex);
}
}
stack.pop();
return foundCycle;
}
private void unblock(Vertex vertex) {
blocked.remove(vertex);
Set bSet = getBSet(vertex);
while (bSet.size() > 0) {
Vertex w = bSet.iterator().next();
bSet.remove(w);
if (blocked.contains(w)) {
unblock(w);
}
}
}
private void initMinSCGState() {
index = 0;
foundSCCs = new ArrayList<>();
vIndex = new LinkedHashMap<>();
vLowlink = new LinkedHashMap<>();
path = new ArrayDeque<>();
pathSet = new LinkedHashSet<>();
}
private void clearMinSCCState() {
index = 0;
foundSCCs = null;
vIndex = null;
vLowlink = null;
path = null;
pathSet = null;
}
private Integer toI(Vertex vertex) {
return vToI.get(vertex);
}
private Vertex toV(Integer i) {
return iToV[i];
}
private Set getBSet(Vertex v) {
// B sets typically not all needed,
// so instantiate lazily.
return bSets.computeIfAbsent(v, k -> new LinkedHashSet<>());
}
}
}
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