fix(core): apply overrides after rendering properties

packages/@aws-cdk/aws-iam/test/test.escape-hatch.ts

@@ -0,0 +1,98 @@
+// tests for the L1 escape hatches (overrides). those are in the IAM module
+// because we want to verify them end-to-end, as a complement to the unit
+// tests in the @aws-cdk/cdk module
+import { expect } from '@aws-cdk/assert';
+import { Stack } from '@aws-cdk/cdk';
+import { Test } from 'nodeunit';
+import iam = require('../lib');
+
+// tslint:disable:object-literal-key-quotes
+
+export = {
+  'addPropertyOverride should allow overriding supported properties'(test: Test) {
+    const stack = new Stack();
+    const user = new iam.User(stack, 'user', {
+      userName: 'MyUserName'
+    });
+
+    const cfn = user.node.findChild('Resource') as iam.CfnUser;
+    cfn.addPropertyOverride('UserName', 'OverriddenUserName');
+
+    expect(stack).toMatch({
+      "Resources": {
+        "user2C2B57AE": {
+          "Type": "AWS::IAM::User",
+          "Properties": {
+            "UserName": "OverriddenUserName"
+          }
+        }
+      }
+    });
+    test.done();
+  },
+  'addPropertyOverrides should allow specifying arbitrary properties'(test: Test) {
+    // GIVEN
+    const stack = new Stack();
+    const user = new iam.User(stack, 'user', { userName: 'MyUserName' });
+    const cfn = user.node.findChild('Resource') as iam.CfnUser;
+
+    // WHEN
+    cfn.addPropertyOverride('Hello.World', 'Boom');
+
+    // THEN
+    expect(stack).toMatch({
+      "Resources": {
+        "user2C2B57AE": {
+          "Type": "AWS::IAM::User",
+          "Properties": {
+            "UserName": "MyUserName",
+            "Hello": {
+              "World": "Boom"
+            }
+          }
+        }
+      }
+    });
+
+    test.done();
+  },
+  'addOverride should allow overriding properties'(test: Test) {
+    // GIVEN
+    const stack = new Stack();
+    const user = new iam.User(stack, 'user', { userName: 'MyUserName' });
+    const cfn = user.node.findChild('Resource') as iam.CfnUser;
+    cfn.options.updatePolicy = { useOnlineResharding: true };
+
+    // WHEN
+    cfn.addOverride('Properties.Hello.World', 'Bam');
+    cfn.addOverride('Properties.UserName', 'HA!');
+    cfn.addOverride('Joob.Jab', 'Jib');
+    cfn.addOverride('Joob.Jab', 'Jib');
+    cfn.addOverride('UpdatePolicy.UseOnlineResharding.Type', 'None');
+
+    // THEN
+    expect(stack).toMatch({
+      "Resources": {
+        "user2C2B57AE": {
+          "Type": "AWS::IAM::User",
+          "Properties": {
+            "UserName": "HA!",
+            "Hello": {
+              "World": "Bam"
+            }
+          },
+          "Joob": {
+            "Jab": "Jib"
+          },
+          "UpdatePolicy": {
+            "UseOnlineResharding": {
+              "Type": "None"
+            }
+          }
+        }
+      }
+    });
+
+    test.done();
+  }
+};

packages/@aws-cdk/cdk/lib/cfn-resource.ts

@@ -234,9 +234,11 @@ export class CfnResource extends CfnRefElement {
             Metadata: ignoreEmpty(this.options.metadata),
             Condition: this.options.condition && this.options.condition.logicalId
           }, props => {
-            const r = deepMerge(props, this.rawOverrides);
-            r.Properties = this.renderProperties(r.Properties);
-            return r;
+            // let derived classes to influence how properties are rendered (e.g. change capitalization)
+            props.Properties = this.renderProperties(props.Properties);
+
+            // merge overrides *after* rendering
+            return deepMerge(props, this.rawOverrides);
           })
         }
       };

packages/@aws-cdk/cdk/test/test.resource.ts

@@ -549,6 +549,38 @@ export = {
       test.done();
     },
 
+    'overrides are applied after render'(test: Test) {
+      // GIVEN
+      class MyResource extends CfnResource {
+        public renderProperties() {
+          return { Fixed: 123 };
+        }
+      }
+      const stack = new Stack();
+      const cfn = new MyResource(stack, 'rr', { type: 'AWS::Resource::Type' });
+
+      // WHEN
+      cfn.addPropertyOverride('Boom', 'Hi');
+      cfn.addOverride('Properties.Foo.Bar', 'Bar');
+
+      // THEN
+      test.deepEqual(stack._toCloudFormation(), {
+        Resources: {
+          rr: {
+            Type: 'AWS::Resource::Type',
+            Properties: {
+              Fixed: 123,
+              Boom: 'Hi',
+              Foo: {
+                Bar: 'Bar'
+              }
+            }
+          }
+        }
+      });
+      test.done();
+    },
+
     'untypedPropertyOverrides': {
 
       'can be used by derived classes to specify overrides before render()'(test: Test) {