feat: pass data types (structs) by-value instead of by-ref

packages/jsii-calc/lib/compliance.ts

@@ -1335,3 +1335,40 @@ export class Constructors {
         return new PrivateClass();
     }
 }
+
+// fixture to verify that null/undefined values in object hashes are treated
+// as "unset". see awslabs/aws-cdk#965.
+export interface EraseUndefinedHashValuesOptions {
+    option1?: string;
+    option2?: string;
+}
+
+export class EraseUndefinedHashValues {
+    /**
+     * Returns `true` if `key` is defined in `opts`. Used to check that undefined/null hash values
+     * are being erased when sending values from native code to JS.
+     */
+    public static doesKeyExist(opts: EraseUndefinedHashValuesOptions, key: string): boolean {
+        return key in opts;
+    }
+
+    /**
+     * We expect "prop2" to be erased
+     */
+    public static prop2IsUndefined(): any {
+        return {
+            prop1: 'value1',
+            prop2: undefined
+        };
+    }
+
+    /**
+     * We expect "prop1" to be erased
+     */
+    public static prop1IsNull(): any {
+        return {
+            prop1: null,
+            prop2: 'value2'
+        };
+    }
+}

packages/jsii-calc/test/assembly.jsii

@@ -1452,6 +1452,86 @@
       ],
       "name": "DoubleTrouble"
     },
+    "jsii-calc.EraseUndefinedHashValues": {
+      "assembly": "jsii-calc",
+      "fqn": "jsii-calc.EraseUndefinedHashValues",
+      "initializer": {
+        "initializer": true
+      },
+      "kind": "class",
+      "methods": [
+        {
+          "docs": {
+            "comment": "Returns `true` if `key` is defined in `opts`. Used to check that undefined/null hash values\nare being erased when sending values from native code to JS."
+          },
+          "name": "doesKeyExist",
+          "parameters": [
+            {
+              "name": "opts",
+              "type": {
+                "fqn": "jsii-calc.EraseUndefinedHashValuesOptions"
+              }
+            },
+            {
+              "name": "key",
+              "type": {
+                "primitive": "string"
+              }
+            }
+          ],
+          "returns": {
+            "primitive": "boolean"
+          },
+          "static": true
+        },
+        {
+          "docs": {
+            "comment": "We expect \"prop1\" to be erased"
+          },
+          "name": "prop1IsNull",
+          "returns": {
+            "primitive": "any"
+          },
+          "static": true
+        },
+        {
+          "docs": {
+            "comment": "We expect \"prop2\" to be erased"
+          },
+          "name": "prop2IsUndefined",
+          "returns": {
+            "primitive": "any"
+          },
+          "static": true
+        }
+      ],
+      "name": "EraseUndefinedHashValues"
+    },
+    "jsii-calc.EraseUndefinedHashValuesOptions": {
+      "assembly": "jsii-calc",
+      "datatype": true,
+      "fqn": "jsii-calc.EraseUndefinedHashValuesOptions",
+      "kind": "interface",
+      "name": "EraseUndefinedHashValuesOptions",
+      "properties": [
+        {
+          "abstract": true,
+          "name": "option1",
+          "type": {
+            "optional": true,
+            "primitive": "string"
+          }
+        },
+        {
+          "abstract": true,
+          "name": "option2",
+          "type": {
+            "optional": true,
+            "primitive": "string"
+          }
+        }
+      ]
+    },
     "jsii-calc.ExportedBaseClass": {
       "assembly": "jsii-calc",
       "fqn": "jsii-calc.ExportedBaseClass",
@@ -3949,5 +4029,5 @@
     }
   },
   "version": "0.7.15",
-  "fingerprint": "IWSOEhdZzuvrss5K2WBjZCawXayV13yCAKTj/kJ9+mo="
+  "fingerprint": "DXEqEDn4p/1Rc0OVCrsby4jumnxo9mWqSNF9sb/laGU="
 }

packages/jsii-java-runtime-test/project/src/test/java/software/amazon/jsii/testing/ComplianceTest.java

@@ -13,6 +13,8 @@
 import software.amazon.jsii.tests.calculator.DerivedStruct;
 import software.amazon.jsii.tests.calculator.DoNotOverridePrivates;
 import software.amazon.jsii.tests.calculator.DoubleTrouble;
+import software.amazon.jsii.tests.calculator.EraseUndefinedHashValues;
+import software.amazon.jsii.tests.calculator.EraseUndefinedHashValuesOptions;
 import software.amazon.jsii.tests.calculator.GiveMeStructs;
 import software.amazon.jsii.tests.calculator.GreetingAugmenter;
 import software.amazon.jsii.tests.calculator.IFriendlier;
@@ -63,6 +65,7 @@
 import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
@@ -982,6 +985,20 @@ public void objRefsAreLabelledUsingWithTheMostCorrectType() {
         assertTrue(ifaceRef instanceof IPublicInterface);
     }
 
+    /**
+     * Verifies that data values that are not set are recognized as unset keys
+     * in JavaScript-land. See https://github.com/awslabs/jsii/issues/375
+     */
+    @Test
+    public void eraseUnsetDataValues() {
+        EraseUndefinedHashValuesOptions opts = EraseUndefinedHashValuesOptions.builder()
+                .withOption1("option1")
+                .build();
+
+        assertTrue(EraseUndefinedHashValues.doesKeyExist(opts, "option1"));
+        assertFalse(EraseUndefinedHashValues.doesKeyExist(opts, "option2"));
+    }
+
     static class MulTen extends Multiply {
         public MulTen(final int value) {
             super(new Number(value), new Number(10));

packages/jsii-java-runtime-test/project/src/test/java/software/amazon/jsii/testing/JsiiClientTest.java

@@ -5,11 +5,14 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.node.ArrayNode;
 import com.fasterxml.jackson.databind.node.JsonNodeFactory;
+import com.fasterxml.jackson.databind.node.ObjectNode;
 import software.amazon.jsii.JsiiClient;
 import software.amazon.jsii.JsiiException;
+import software.amazon.jsii.JsiiObjectMapper;
 import software.amazon.jsii.JsiiObjectRef;
 import software.amazon.jsii.JsiiPromise;
 import software.amazon.jsii.JsiiRuntime;
+import software.amazon.jsii.JsiiSerializable;
 import software.amazon.jsii.api.Callback;
 import software.amazon.jsii.api.JsiiOverride;
 import org.junit.Before;
@@ -217,6 +220,25 @@ public void staticMethods() {
         assertEquals("hello ,Foo!", result.textValue());
     }
 
+    /**
+     * If a JsiiSerializable object has a method named "$jsii$toJson", it will be
+     * used to serialize the object instead of the normal
+     */
+    @Test
+    public void serializeViaJsiiToJsonIfExists() {
+        JsiiObjectMapper om = JsiiObjectMapper.instance;
+        JsonNode result = om.valueToTree(new JsiiSerializable() {
+            public JsonNode $jsii$toJson() {
+                ObjectNode node = JSON.objectNode();
+                node.set("foo", OM.valueToTree("bar"));
+                node.set("hey", OM.valueToTree(42));
+                return node;
+            }
+        });
+
+        assertEquals("{\"foo\":\"bar\",\"hey\":42}", result.toString());
+    }
+
     private ArrayNode toSandboxArray(final Object... values) {
         return OM.valueToTree(values);
     }

packages/jsii-java-runtime/project/src/main/java/software/amazon/jsii/JsiiClient.java

@@ -35,7 +35,7 @@ public final class JsiiClient {
     /**
      * Jsii custom object mapper.
      */
-    private static final JsiiObjectMapper JSII_OM = new JsiiObjectMapper();
+    private static final JsiiObjectMapper JSII_OM = JsiiObjectMapper.instance;
 
     /**
      * TCP port to connect to (always "localhost").

packages/jsii-java-runtime/project/src/main/java/software/amazon/jsii/JsiiEngine.java

@@ -48,7 +48,7 @@ public final class JsiiEngine implements JsiiCallbackHandler {
     /**
      * JSON object mapper.
      */
-    private static final JsiiObjectMapper OM = new JsiiObjectMapper();
+    private static final JsiiObjectMapper OM = JsiiObjectMapper.instance;
 
     /**
      * The set of modules we already loaded into the VM.

packages/jsii-java-runtime/project/src/main/java/software/amazon/jsii/JsiiObject.java

@@ -1,6 +1,7 @@
 package software.amazon.jsii;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.core.TreeNode;
 import com.fasterxml.jackson.databind.JsonNode;
 
 import javax.annotation.Nullable;
@@ -13,7 +14,7 @@ public class JsiiObject implements JsiiSerializable {
     /**
      * JSON object mapper.
      */
-    private static final JsiiObjectMapper OM = new JsiiObjectMapper();
+    private static final JsiiObjectMapper OM = JsiiObjectMapper.instance;
 
     /**
      * The jsii engine used by this object.