add support for map.set in Immutable model

Author: erik-krogh

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

@@ -50,7 +50,12 @@ private module Immutable {
       pred = call.getOptionArgument(0, key) and
       result = call
     )
-    // TODO: map set.
+    or
+    exists(DataFlow::CallNode call | call = immutableMap().getMember("set").getACall() |
+      prop = mapValue(call.getArgument(0)) and
+      pred = call.getArgument(1) and
+      result = call
+    )
   }
 
   /**

javascript/ql/test/library-tests/frameworks/Immutable/immutable.js

@@ -12,4 +12,6 @@ sink(map1.get("a")); // NOT OK
 sink(map2.get("a")); // NOT OK
 sink(map2.get("b")); // OK - but still flagged [INCONSISTENCY]
 
-
+const map3 = map2.set("d", source("d"));
+sink(map1.get("d")); // OK
+sink(map3.get("d")); // NOT OK

javascript/ql/test/library-tests/frameworks/Immutable/tests.expected

@@ -3,3 +3,4 @@
 | immutable.js:1:16:1:26 | source("a") | immutable.js:12:6:12:18 | map2.get("a") |
 | immutable.js:1:32:1:43 | source("b1") | immutable.js:8:6:8:18 | map1.get("b") |
 | immutable.js:1:32:1:43 | source("b1") | immutable.js:13:6:13:18 | map2.get("b") |
+| immutable.js:15:28:15:38 | source("d") | immutable.js:17:6:17:18 | map3.get("d") |