JS: support React shouldComponentUpdate

Author: Esben Sparre Andreasen

javascript/ql/src/semmle/javascript/frameworks/React.qll

@@ -182,6 +182,9 @@ abstract class ReactComponent extends ASTNode {
     )
     or
     result.flowsToExpr(getStaticMethod("getDerivedStateFromProps").getAReturnedExpr())
+    or
+    // shouldComponentUpdate: (nextProps, nextState)
+    result = DataFlow::parameterNode(getInstanceMethod("shouldComponentUpdate").getParameter(1))
   }
 
   /**
@@ -216,6 +219,9 @@ abstract class ReactComponent extends ASTNode {
     result.flowsTo(getComponentCreatorSource().getAnInvocation().getArgument(0))
     or
     result = getADefaultPropsSource()
+    or
+    // shouldComponentUpdate: (nextProps, nextState)
+    result = DataFlow::parameterNode(getInstanceMethod("shouldComponentUpdate").getParameter(0))
   }
 
   /**

javascript/ql/test/library-tests/frameworks/ReactJS/ReactComponent_getACandidateStateSource.expected

@@ -1,5 +1,6 @@
 | es6.js:14:1:20:1 | class H ...     }\\n} | es6.js:18:22:18:31 | { baz: 42} |
 | rare-lifecycle-methods.js:1:1:11:1 | class C ...     }\\n} | rare-lifecycle-methods.js:3:16:3:17 | {} |
+| rare-lifecycle-methods.js:1:1:11:1 | class C ...     }\\n} | rare-lifecycle-methods.js:5:38:5:46 | nextState |
 | statePropertyReads.js:1:1:13:1 | class R ...     }\\n} | statePropertyReads.js:7:45:7:56 | prevState.p3 |
 | statePropertyWrites.js:1:1:34:1 | class W ...    };\\n} | statePropertyWrites.js:8:18:8:19 | {} |
 | statePropertyWrites.js:1:1:34:1 | class W ...    };\\n} | statePropertyWrites.js:12:18:12:19 | {} |