Add method-result-ignored.ql

Author: Marcono1234

codeql-custom-queries-java/queries/likely-bugs/method-result-ignored.ql

@@ -0,0 +1,55 @@
+/**
+ * Finds method calls where the result of the call is ignored, despite the method being
+ * annotated with `@CheckReturnValue`.
+ * 
+ * See also Error Prone pattern [CheckReturnValue](https://errorprone.info/bugpattern/CheckReturnValue).
+ * 
+ * @kind problem
+ */
+
+// This is also detected by IntelliJ IDEA, see https://youtrack.jetbrains.com/issue/IDEA-153192 and https://youtrack.jetbrains.com/issue/IDEA-158576
+
+// Similar to CodeQL's `java/return-value-ignored` and `java/ignored-error-status-of-call`
+
+import java
+
+class CheckReturnValueAnnotation extends Annotation {
+    CheckReturnValueAnnotation() {
+        // Note: Ignore package name because annotation exists for JSR 305, Error Prone annotations, and SpotBugs annotations, ...
+        getType().hasName("CheckReturnValue")
+    }
+}
+
+class CanIgnoreReturnValueAnnotation extends Annotation {
+    CanIgnoreReturnValueAnnotation() {
+        // Note: Currently seems to only exist for Error Prone annotations, but to avoid false positives ignore the
+        // package name here as well
+        getType().hasName("CanIgnoreReturnValue")
+    }
+}
+
+from MethodAccess call, Method m, RefType declaringType
+where
+    // Result of method call is ignored
+    call instanceof ValueDiscardingExpr
+    and m = call.getMethod().getSourceDeclaration()
+    and declaringType = m.getDeclaringType()
+    // Ignore if method has no return value (but declaring type might be annotated with CheckReturnValue)
+    and not m.getReturnType() instanceof VoidType
+    and (
+        m.getAnAnnotation() instanceof CheckReturnValueAnnotation
+        or
+        not m.getAnAnnotation() instanceof CanIgnoreReturnValueAnnotation
+        and (
+            declaringType.getAnAnnotation() instanceof CheckReturnValueAnnotation
+            or (
+                declaringType.getPackage().getAnAnnotation() instanceof CheckReturnValueAnnotation
+                and not declaringType.getAnAnnotation() instanceof CanIgnoreReturnValueAnnotation
+            )
+        )
+    )
+    // Ignore test classes
+    // TODO: If possible make this more specific; there are cases where results in test classes
+    // are relevant as well, for example incorrect usage of AssertJ
+    and not call.getEnclosingCallable().getDeclaringType() instanceof TestClass
+select call, "Result of this call should not be ignored"