[GR-26744] JSON.stringify() should try to use toJSON() of foreign objects.

PullRequest: js/1721

Author: Stefan Anzinger

graal-js/src/com.oracle.truffle.js.test/src/com/oracle/truffle/js/test/interop/JSONStringifyInteropTest.java

@@ -51,6 +51,8 @@
 import org.graalvm.polyglot.Context;
 import org.graalvm.polyglot.HostAccess;
 import org.graalvm.polyglot.Value;
+import org.graalvm.polyglot.proxy.ProxyExecutable;
+import org.graalvm.polyglot.proxy.ProxyObject;
 import org.junit.Test;
 
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
@@ -85,12 +87,38 @@ public void testForeignExecutable() {
         }
     }
 
+    private static void checkStringification(Object objectToStringify, String expectedResult) {
+        try (Context context = JSTest.newContextBuilder().allowHostAccess(HostAccess.ALL).build()) {
+            context.getBindings(ID).putMember("objectToStringify", objectToStringify);
+            Value result = context.eval(ID, "JSON.stringify(objectToStringify)");
+            assertEquals(expectedResult, result.asString());
+        }
+    }
+
     @Test
     public void testNonReadableMembers() {
-        try (Context context = JSTest.newContextBuilder().allowHostAccess(HostAccess.ALL).build()) {
-            context.getBindings(ID).putMember("myObj", new InvocableMemberObject(Collections.singletonMap("someKey", "someValue")));
-            Value result = context.eval(ID, "JSON.stringify(myObj)");
-            assertEquals("{}", result.asString());
+        checkStringification(new InvocableMemberObject(Collections.singletonMap("someKey", "someValue")), "{}");
+    }
+
+    @Test
+    public void testToJSONOfProxyObject() {
+        Object object = ProxyObject.fromMap(Collections.singletonMap("toJSON", new ProxyExecutable() {
+            @Override
+            public Object execute(Value... arguments) {
+                return "fromToJSON";
+            }
+        }));
+        checkStringification(object, "\"fromToJSON\"");
+    }
+
+    @Test
+    public void testToJSONOfHostObject() {
+        checkStringification(new HostObjectWithToJSON(), "\"HostObjectWithToJSON\"");
+    }
+
+    public static class HostObjectWithToJSON {
+        public Object toJSON(@SuppressWarnings("unused") String key) {
+            return "HostObjectWithToJSON";
         }
     }
 

graal-js/src/com.oracle.truffle.js/src/com/oracle/truffle/js/builtins/helper/JSONStringifyStringNode.java

@@ -199,7 +199,14 @@ private Object jsonStrPrepareForeign(JSONData data, int key, Object holder) {
 
     private Object jsonStrPreparePart2(JSONData data, String key, Object holder, Object valueArg) {
         Object value = valueArg;
+        boolean tryToJSON = false;
         if (JSRuntime.isObject(value) || JSRuntime.isBigInt(value)) {
+            tryToJSON = true;
+        } else if (JSRuntime.isForeignObject(value)) {
+            InteropLibrary interop = InteropLibrary.getUncached(value);
+            tryToJSON = interop.hasMembers(value) && !interop.isNull(value) && !interop.isBoolean(value) && !interop.isString(value) && !interop.isNumber(value);
+        }
+        if (tryToJSON) {
             value = jsonStrPrepareObject(key, value);
         }
 
@@ -241,12 +248,12 @@ private Object jsonStrPrepareObject(Object key, Object value) {
         }
         Object toJSON = getToJSONProperty.getValue(value);
         if (JSRuntime.isCallable(toJSON)) {
-            return jsonStrPrepareObjectFunction(key, value, (DynamicObject) toJSON);
+            return jsonStrPrepareObjectFunction(key, value, toJSON);
         }
         return value;
     }
 
-    private Object jsonStrPrepareObjectFunction(Object key, Object value, DynamicObject toJSON) {
+    private Object jsonStrPrepareObjectFunction(Object key, Object value, Object toJSON) {
         if (callToJSONFunction == null) {
             CompilerDirectives.transferToInterpreterAndInvalidate();
             callToJSONFunction = insert(JSFunctionCallNode.createCall());