Fix ArrayIndexOutOfBoundsException in empty ChainedInstrumentation (graphql-java#781)

ind1go · bbakerman · commit 94092980e37d · 2017-10-17T18:03:39.000+11:00
* Failing test for empty ChainedInstrumentation * Fix exception in empty ChainedInstrumentation (graphql-java#780)
diff --git a/src/main/java/graphql/execution/instrumentation/ChainedInstrumentation.java b/src/main/java/graphql/execution/instrumentation/ChainedInstrumentation.java
@@ -137,7 +137,7 @@ public CompletableFuture<ExecutionResult> instrumentExecutionResult(ExecutionRes
             ExecutionResult lastResult = prevResults.size() > 0 ? prevResults.get(prevResults.size() - 1) : executionResult;
             return instrumentation.instrumentExecutionResult(lastResult, parameters.withNewState(state));
         });
-        return resultsFuture.thenApply((results) -> results.get(results.size() - 1));
+        return resultsFuture.thenApply((results) -> results.isEmpty() ? executionResult : results.get(results.size() - 1));
     }
 
     private static class ChainedInstrumentationState implements InstrumentationState {
diff --git a/src/test/groovy/graphql/execution/instrumentation/ChainedInstrumentationStateTest.groovy b/src/test/groovy/graphql/execution/instrumentation/ChainedInstrumentationStateTest.groovy
@@ -175,6 +175,32 @@ class ChainedInstrumentationStateTest extends Specification {
 
     }
 
+    def "empty chain"() {
+        def chainedInstrumentation = new ChainedInstrumentation(Arrays.asList())
+
+        def query = """
+        query HeroNameAndFriendsQuery {
+            hero {
+                id
+            }
+        }
+        """
+
+        when:
+        def strategy = new AsyncExecutionStrategy()
+        def graphQL = GraphQL
+                .newGraphQL(StarWarsSchema.starWarsSchema)
+                .queryExecutionStrategy(strategy)
+                .instrumentation(chainedInstrumentation)
+                .build()
+
+        graphQL.execute(query)
+
+        then:
+        noExceptionThrown()
+
+    }
+
     private void assertCalls(NamedInstrumentation instrumentation) {
         assert instrumentation.dfInvocations[0].getFieldDefinition().name == 'hero'
         assert instrumentation.dfInvocations[0].getFieldTypeInfo().getPath().toList() == ['hero']

Original file line number	Diff line number	Diff line change
`@@ -137,7 +137,7 @@ public CompletableFuture<ExecutionResult> instrumentExecutionResult(ExecutionRes`
`137`	`137`	`ExecutionResult lastResult = prevResults.size() > 0 ? prevResults.get(prevResults.size() - 1) : executionResult;`
`138`	`138`	`return instrumentation.instrumentExecutionResult(lastResult, parameters.withNewState(state));`
`139`	`139`	`});`
`140`		`- return resultsFuture.thenApply((results) -> results.get(results.size() - 1));`
	`140`	`+ return resultsFuture.thenApply((results) -> results.isEmpty() ? executionResult : results.get(results.size() - 1));`
`141`	`141`	`}`
`142`	`142`
`143`	`143`	`private static class ChainedInstrumentationState implements InstrumentationState {`