JS: fixup optional chaining on CallWithNonLocalAnalyzedReturnFlow

Author: Esben Sparre Andreasen

javascript/ql/src/semmle/javascript/dataflow/internal/InterProceduralTypeInference.qll

@@ -157,6 +157,10 @@ abstract class CallWithNonLocalAnalyzedReturnFlow extends DataFlow::AnalyzedValu
 
   override AbstractValue getAValue() {
     result = getACallee().getAReturnValue()
+    or
+    // special case from the local layer (could be more precise if it is inferred that the callee is not `null`/`undefined`)
+    astNode instanceof OptionalChainRoot and
+    result = TAbstractUndefined()
   }
 }
 

javascript/ql/test/library-tests/TypeInference/OptionalChaining/test.expected

@@ -9,6 +9,14 @@
 | tst.js:7:14:7:26 | (unknown)?.() | file://:0:0:0:0 | undefined |
 | tst.js:9:13:11:5 | unknown ... ;\\n    } | file://:0:0:0:0 | undefined |
 | tst.js:9:13:11:5 | unknown ... ;\\n    } | tst.js:9:33:11:5 | anonymous function |
-| tst.js:12:14:12:16 | f() | file://:0:0:0:0 | indefinite value (call) |
-| tst.js:13:14:13:18 | f?.() | file://:0:0:0:0 | indefinite value (call) |
+| tst.js:12:14:12:16 | f() | file://:0:0:0:0 | non-zero value |
+| tst.js:13:14:13:18 | f?.() | file://:0:0:0:0 | non-zero value |
 | tst.js:13:14:13:18 | f?.() | file://:0:0:0:0 | undefined |
+| tst.js:15:13:17:5 | functio ... ;\\n    } | tst.js:15:13:17:5 | function g |
+| tst.js:18:14:18:16 | g() | file://:0:0:0:0 | non-zero value |
+| tst.js:19:15:19:19 | g?.() | file://:0:0:0:0 | non-zero value |
+| tst.js:19:15:19:19 | g?.() | file://:0:0:0:0 | undefined |
+| tst.js:21:13:21:21 | undefined | file://:0:0:0:0 | undefined |
+| tst.js:22:15:22:17 | h() | file://:0:0:0:0 | indefinite value (call) |
+| tst.js:23:15:23:19 | h?.() | file://:0:0:0:0 | indefinite value (call) |
+| tst.js:23:15:23:19 | h?.() | file://:0:0:0:0 | undefined |

javascript/ql/test/library-tests/TypeInference/OptionalChaining/tst.js

@@ -8,8 +8,18 @@
 
     var f = unknown? undefined: function(){
         return 42;
-    }
+    };
     var v7 = f();
     var v8 = f?.();
+
+    var g = function(){
+        return 42;
+    };
+    var v9 = g();
+    var v10 = g?.();
+
+    var h = undefined;
+    var v11 = h();
+    var v12 = h?.();
 });
 // semmle-extractor-options: --experimental