fix(jsii-runtime): treat "null" as "undefined"

packages/jsii-calc/lib/compliance.ts

@@ -948,3 +948,49 @@ export class DoNotRecognizeAnyAsOptional {
 
     }
 }
+
+/**
+ * jsii#282, aws-cdk#157: null should be treated as "undefined"
+ */
+export class NullShouldBeTreatedAsUndefined {
+    public changeMeToUndefined? = "hello";
+
+    constructor(_param1: string, optional?: any) {
+        if (optional !== undefined) {
+            throw new Error('Expecting second constructor argument to be "undefined"');
+        }
+    }
+
+    public giveMeUndefined(value?: any) {
+        if (value !== undefined) {
+            throw new Error('I am disappointed. I expected undefined and got: ' + JSON.stringify(value));
+        }
+    }
+
+    public giveMeUndefinedInsideAnObject(input: NullShouldBeTreatedAsUndefinedData) {
+        if (input.thisShouldBeUndefined !== undefined) {
+            throw new Error('I am disappointed. I expected undefined in "thisShouldBeUndefined" and got: ' + JSON.stringify(input));
+        }
+
+        const array = input.arrayWithThreeElementsAndUndefinedAsSecondArgument;
+        if (array.length !== 3) {
+            throw new Error('Expecting "arrayWithThreeElementsAndUndefinedAsSecondArgument" to have three elements: ' + JSON.stringify(input));
+        }
+
+        if (array[1] !== undefined) {
+            throw new Error('Expected arrayWithThreeElementsAndUndefinedAsSecondArgument[1] to be undefined: ' + JSON.stringify(input))
+        }
+    }
+
+    public verifyPropertyIsUndefined() {
+        if (this.changeMeToUndefined !== undefined) {
+            throw new Error('Expecting property "changeMeToUndefined" to be undefined, and it is: ' + this.changeMeToUndefined);
+        }
+    }
+}
+
+export interface NullShouldBeTreatedAsUndefinedData {
+    thisShouldBeUndefined?: any;
+    arrayWithThreeElementsAndUndefinedAsSecondArgument: any[];
+}
+

packages/jsii-calc/test/assembly.jsii

@@ -2273,6 +2273,99 @@
         }
       ]
     },
+    "jsii-calc.NullShouldBeTreatedAsUndefined": {
+      "assembly": "jsii-calc",
+      "docs": {
+        "comment": "jsii#282, aws-cdk#157: null should be treated as \"undefined\""
+      },
+      "fqn": "jsii-calc.NullShouldBeTreatedAsUndefined",
+      "initializer": {
+        "initializer": true,
+        "parameters": [
+          {
+            "name": "_param1",
+            "type": {
+              "primitive": "string"
+            }
+          },
+          {
+            "name": "optional",
+            "type": {
+              "optional": true,
+              "primitive": "any"
+            }
+          }
+        ]
+      },
+      "kind": "class",
+      "methods": [
+        {
+          "name": "giveMeUndefined",
+          "parameters": [
+            {
+              "name": "value",
+              "type": {
+                "optional": true,
+                "primitive": "any"
+              }
+            }
+          ]
+        },
+        {
+          "name": "giveMeUndefinedInsideAnObject",
+          "parameters": [
+            {
+              "name": "input",
+              "type": {
+                "fqn": "jsii-calc.NullShouldBeTreatedAsUndefinedData"
+              }
+            }
+          ]
+        },
+        {
+          "name": "verifyPropertyIsUndefined"
+        }
+      ],
+      "name": "NullShouldBeTreatedAsUndefined",
+      "properties": [
+        {
+          "name": "changeMeToUndefined",
+          "type": {
+            "optional": true,
+            "primitive": "string"
+          }
+        }
+      ]
+    },
+    "jsii-calc.NullShouldBeTreatedAsUndefinedData": {
+      "assembly": "jsii-calc",
+      "datatype": true,
+      "fqn": "jsii-calc.NullShouldBeTreatedAsUndefinedData",
+      "kind": "interface",
+      "name": "NullShouldBeTreatedAsUndefinedData",
+      "properties": [
+        {
+          "abstract": true,
+          "name": "arrayWithThreeElementsAndUndefinedAsSecondArgument",
+          "type": {
+            "collection": {
+              "elementtype": {
+                "primitive": "any"
+              },
+              "kind": "array"
+            }
+          }
+        },
+        {
+          "abstract": true,
+          "name": "thisShouldBeUndefined",
+          "type": {
+            "optional": true,
+            "primitive": "any"
+          }
+        }
+      ]
+    },
     "jsii-calc.NumberGenerator": {
       "assembly": "jsii-calc",
       "docs": {
@@ -3444,5 +3537,5 @@
     }
   },
   "version": "0.7.8",
-  "fingerprint": "2BaszImarh4WChl9DFUcygfTpEfXU17fHQT2wgEptfM="
+  "fingerprint": "FZk0ePQ2XUte84CmnOjU3PPCl6QUA88ke6wHIJKhyzo="
 }

packages/jsii-dotnet-runtime-test/test/Amazon.JSII.Runtime.IntegrationTests/ComplianceTests.cs

@@ -827,6 +827,27 @@ public void TestReturnInterfaceFromOverride()
             Assert.Equal(4 * n, obj.Test(arg));
         }
 
+        [Fact(DisplayName = Prefix + nameof(NullShouldBeTreatedAsUndefined))]
+        public void NullShouldBeTreatedAsUndefined()
+        {
+            // ctor
+            var obj = new NullShouldBeTreatedAsUndefined("param1", null);
+
+            // method argument
+            obj.GiveMeUndefined(null);
+
+            // inside object
+            obj.GiveMeUndefinedInsideAnObject(new NullShouldBeTreatedAsUndefinedData
+            {
+                ThisShouldBeUndefined = null,
+                ArrayWithThreeElementsAndUndefinedAsSecondArgument = new[] { "hello", null, "world" }
+            });
+
+            // property
+            obj.ChangeMeToUndefined = null;
+            obj.VerifyPropertyIsUndefined();
+        }
+
         class NumberReturner : DeputyBase, IIReturnsNumber
         {
             public NumberReturner(double number)

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

@@ -25,6 +25,8 @@
 import software.amazon.jsii.tests.calculator.Multiply;
 import software.amazon.jsii.tests.calculator.Negate;
 import software.amazon.jsii.tests.calculator.NodeStandardLibrary;
+import software.amazon.jsii.tests.calculator.NullShouldBeTreatedAsUndefined;
+import software.amazon.jsii.tests.calculator.NullShouldBeTreatedAsUndefinedData;
 import software.amazon.jsii.tests.calculator.NumberGenerator;
 import software.amazon.jsii.tests.calculator.Polymorphism;
 import software.amazon.jsii.tests.calculator.Power;
@@ -927,6 +929,18 @@ public void classWithPrivateConstructorAndAutomaticProperties() {
         assertEquals("Hello", obj.getReadOnlyString());
     }
 
+    @Test
+    public void nullShouldBeTreatedAsUndefined() {
+        NullShouldBeTreatedAsUndefined obj = new NullShouldBeTreatedAsUndefined("hello", null);
+        obj.giveMeUndefined(null);
+        obj.giveMeUndefinedInsideAnObject(NullShouldBeTreatedAsUndefinedData.builder()
+                .withThisShouldBeUndefined(null)
+                .withArrayWithThreeElementsAndUndefinedAsSecondArgument(Arrays.asList("hello", null, "boom"))
+                .build());
+        obj.setChangeMeToUndefined(null);
+        obj.verifyPropertyIsUndefined();
+    }
+
     static class MulTen extends Multiply {
         public MulTen(final int value) {
             super(new Number(value), new Number(10));

packages/jsii-kernel/lib/kernel.ts

@@ -877,9 +877,10 @@ export class Kernel {
             return undefined;
         }
 
-        // null
+        // null is treated as "undefined" because most languages do not have this distinction
+        // see awslabs/aws-cdk#157 and awslabs/jsii#282
         if (v === null) {
-            return null;
+            return undefined;
         }
 
         // pointer

packages/jsii-kernel/test/test.kernel.ts

@@ -936,6 +936,29 @@ defineTest('overrides: skip overrides of private properties', async (test, sandb
     test.deepEqual(result.result, 'privateProperty');
 });
 
+defineTest('nulls are converted to undefined - ctor', async (_test, sandbox) => {
+    sandbox.create({ fqn: 'jsii-calc.NullShouldBeTreatedAsUndefined', args: [ "foo", null ] });
+});
+
+defineTest('nulls are converted to undefined - method arguments', async (_test, sandbox) => {
+    const objref = sandbox.create({ fqn: 'jsii-calc.NullShouldBeTreatedAsUndefined', args: [ "foo" ] });
+    sandbox.invoke({ objref, method: 'giveMeUndefined', args: [ null ] });
+});
+
+defineTest('nulls are converted to undefined - inside objects', async (_test, sandbox) => {
+    const objref = sandbox.create({ fqn: 'jsii-calc.NullShouldBeTreatedAsUndefined', args: [ "foo" ] });
+    sandbox.invoke({ objref, method: 'giveMeUndefinedInsideAnObject', args: [ {
+        thisShouldBeUndefined: null,
+        arrayWithThreeElementsAndUndefinedAsSecondArgument: [ 'one', null, 'two' ]
+    } ]});
+});
+
+defineTest('nulls are converted to undefined - properties', async (_test, sandbox) => {
+    const objref = sandbox.create({ fqn: 'jsii-calc.NullShouldBeTreatedAsUndefined', args: [ "foo" ] });
+    sandbox.set({ objref, property: 'changeMeToUndefined', value: null });
+    sandbox.invoke({ objref, method: 'verifyPropertyIsUndefined' });
+});
+
 // =================================================================================================
 
 const testNames: { [name: string]: boolean } = { };

packages/jsii-pacmak/test/expected.jsii-calc/dotnet/Amazon.JSII.Tests.CalculatorPackageId/.jsii

@@ -2273,6 +2273,99 @@
         }
       ]
     },
+    "jsii-calc.NullShouldBeTreatedAsUndefined": {
+      "assembly": "jsii-calc",
+      "docs": {
+        "comment": "jsii#282, aws-cdk#157: null should be treated as \"undefined\""
+      },
+      "fqn": "jsii-calc.NullShouldBeTreatedAsUndefined",
+      "initializer": {
+        "initializer": true,
+        "parameters": [
+          {
+            "name": "_param1",
+            "type": {
+              "primitive": "string"
+            }
+          },
+          {
+            "name": "optional",
+            "type": {
+              "optional": true,
+              "primitive": "any"
+            }
+          }
+        ]
+      },
+      "kind": "class",
+      "methods": [
+        {
+          "name": "giveMeUndefined",
+          "parameters": [
+            {
+              "name": "value",
+              "type": {
+                "optional": true,
+                "primitive": "any"
+              }
+            }
+          ]
+        },
+        {
+          "name": "giveMeUndefinedInsideAnObject",
+          "parameters": [
+            {
+              "name": "input",
+              "type": {
+                "fqn": "jsii-calc.NullShouldBeTreatedAsUndefinedData"
+              }
+            }
+          ]
+        },
+        {
+          "name": "verifyPropertyIsUndefined"
+        }
+      ],
+      "name": "NullShouldBeTreatedAsUndefined",
+      "properties": [
+        {
+          "name": "changeMeToUndefined",
+          "type": {
+            "optional": true,
+            "primitive": "string"
+          }
+        }
+      ]
+    },
+    "jsii-calc.NullShouldBeTreatedAsUndefinedData": {
+      "assembly": "jsii-calc",
+      "datatype": true,
+      "fqn": "jsii-calc.NullShouldBeTreatedAsUndefinedData",
+      "kind": "interface",
+      "name": "NullShouldBeTreatedAsUndefinedData",
+      "properties": [
+        {
+          "abstract": true,
+          "name": "arrayWithThreeElementsAndUndefinedAsSecondArgument",
+          "type": {
+            "collection": {
+              "elementtype": {
+                "primitive": "any"
+              },
+              "kind": "array"
+            }
+          }
+        },
+        {
+          "abstract": true,
+          "name": "thisShouldBeUndefined",
+          "type": {
+            "optional": true,
+            "primitive": "any"
+          }
+        }
+      ]
+    },
     "jsii-calc.NumberGenerator": {
       "assembly": "jsii-calc",
       "docs": {
@@ -3444,5 +3537,5 @@
     }
   },
   "version": "0.7.8",
-  "fingerprint": "2BaszImarh4WChl9DFUcygfTpEfXU17fHQT2wgEptfM="
+  "fingerprint": "FZk0ePQ2XUte84CmnOjU3PPCl6QUA88ke6wHIJKhyzo="
 }

packages/jsii-pacmak/test/expected.jsii-calc/dotnet/Amazon.JSII.Tests.CalculatorPackageId/Amazon/JSII/Tests/CalculatorNamespace/INullShouldBeTreatedAsUndefinedData.cs

@@ -0,0 +1,22 @@
+using Amazon.JSII.Runtime.Deputy;
+
+namespace Amazon.JSII.Tests.CalculatorNamespace
+{
+    [JsiiInterface(typeof(INullShouldBeTreatedAsUndefinedData), "jsii-calc.NullShouldBeTreatedAsUndefinedData")]
+    public interface INullShouldBeTreatedAsUndefinedData
+    {
+        [JsiiProperty("arrayWithThreeElementsAndUndefinedAsSecondArgument", "{\"collection\":{\"kind\":\"array\",\"elementtype\":{\"primitive\":\"any\"}}}")]
+        object[] ArrayWithThreeElementsAndUndefinedAsSecondArgument
+        {
+            get;
+            set;
+        }
+
+        [JsiiProperty("thisShouldBeUndefined", "{\"primitive\":\"any\",\"optional\":true}")]
+        object ThisShouldBeUndefined
+        {
+            get;
+            set;
+        }
+    }
+}