Fix issue karatelabs#2406

karate-core/src/main/java/com/intuit/karate/core/Variable.java

@@ -49,6 +49,8 @@ public class Variable {
 
     public static enum Type {
         NULL,
+        // add undefined (to differ from null)
+        UNDEFINED,
         BOOLEAN,
         NUMBER,
         STRING,

karate-core/src/main/java/com/intuit/karate/graal/JsValue.java

@@ -66,9 +66,14 @@ public JsValue(Value v) {
         }
         this.original = v;
         try {
-            if (v.isNull()) {
+            if (v.isNull() && v.toString().equals("null")) {
                 value = null;
                 type = Type.NULL;
+            } else if (v.isNull() && v.toString().equals("undefined")) {
+                // if v is undefined, convert it to #notpresent,
+                // which semantically matches to undefined
+                type = Type.OTHER;
+                value = "#notpresent";
             } else if (v.isHostObject()) {
                 if (v.isMetaObject()) { // java.lang.Class !
                     value = v; // special case, keep around as graal value

karate-e2e-tests/src/test/java/json/NullTest.java

@@ -0,0 +1,29 @@
+package json;
+
+import com.intuit.karate.Results;
+import com.intuit.karate.Runner;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class NullTest {
+    void shouldFail(String name) {
+        Results results = Runner.path("src/test/java/json/" + name + ".feature").parallel(1);
+        assertEquals(1, results.getFailCount(), results.getErrorMessages());
+    }
+
+    @Test
+    void testEmptyObject() {
+        shouldFail("empty-object");
+    }
+
+    @Test
+    void testEmptyString() {
+        shouldFail("empty-string");
+    }
+
+    @Test
+    void testRecommend() {
+        shouldFail("recommend");
+    }
+}

karate-e2e-tests/src/test/java/json/empty-object.feature

@@ -0,0 +1,6 @@
+Feature:
+
+  Scenario: empty object should fail:
+    * def response = {}
+    * match response.id == '#null'
+    * match response.time == '#present'

karate-e2e-tests/src/test/java/json/empty-string.feature

@@ -0,0 +1,6 @@
+Feature:
+
+  Scenario: empty reponse should fail:
+    * def response = ''
+    * match response.time == '#present'
+    * match response.id == '#null'

karate-e2e-tests/src/test/java/json/recommend.feature

@@ -0,0 +1,5 @@
+Feature:
+
+  Scenario: recommended to use should not fail:
+    * def response = ''
+    * match response == { id: '#null', time: '#present' }