JS: Add test for taint propagating into RegExp.$1

javascript/ql/test/library-tests/TaintTracking/static-capture-groups.js

@@ -0,0 +1,45 @@
+function test(x) {
+    let taint = source();
+
+    if (/Hello (.*)/.exec(taint)) {
+        sink(RegExp.$1); // NOT OK
+    }
+
+    if (/Foo (.*)/.exec(x)) {
+        sink(RegExp.$1); // OK
+    } else {
+        sink(RegExp.$1); // NOT OK - previous capture group remains
+    }
+
+    if (/Hello ([a-zA-Z]+)/.exec(taint)) {
+        sink(RegExp.$1); // OK - capture group is sanitized
+    } else {
+        sink(RegExp.$1); // NOT OK - original capture group possibly remains
+    }
+
+    if (/Hello (.*)/.exec(taint) && something()) {
+        sink(RegExp.$1); // NOT OK
+    }
+    if (something() && /Hello (.*)/.exec(taint)) {
+        sink(RegExp.$1); // NOT OK
+    }
+    if (/First (.*)/.exec(taint) || /Second (.*)/.exec(taint)) {
+        sink(RegExp.$1); // NOT OK
+    }
+}
+
+function test2(x) {
+    var taint = source();
+    if (something()) {
+        if (/Hello (.*)/.exec(taint)) {
+            something();
+        }
+    }
+    sink(RegExp.$1); // NOT OK
+}
+
+function replaceCallback() {
+    return source().replace(/(\w+)/, () => {
+        sink(RegExp.$1); // NOT OK
+    });
+}