[Composition] Disallow composition for leaf types

Disallow composition for domain object types which will
not have a composition property; WTD-1221.

platform/commonUI/browse/src/creation/CreateWizard.js

@@ -45,8 +45,9 @@ define(
                 properties = type.getProperties();
 
             function validateLocation(locatingObject) {
-                var locatingType = locatingObject.getCapability('type');
-                return policyService.allow(
+                var locatingType = locatingObject &&
+                        locatingObject.getCapability('type');
+                return locatingType && policyService.allow(
                     "composition",
                     locatingType,
                     type

platform/containment/bundle.json

@@ -12,6 +12,11 @@
                 "implementation": "CompositionMutabilityPolicy.js",
                 "message": "Objects of this type cannot be modified."
             },
+            {
+                "category": "composition",
+                "implementation": "CompositionModelPolicy.js",
+                "message": "Objects of this type cannot contain other objects."
+            },
             {
                 "category": "action",
                 "implementation": "ComposeActionPolicy.js",

platform/containment/src/CompositionModelPolicy.js

@@ -0,0 +1,28 @@
+/*global define*/
+
+define(
+    [],
+    function () {
+        "use strict";
+
+        /**
+         * Policy allowing composition only for domain object types which
+         * have a composition property.
+         */
+        function CompositionModelPolicy() {
+            return {
+                /**
+                 * Is the type identified by the candidate allowed to
+                 * contain the type described by the context?
+                 */
+                allow: function (candidate, context) {
+                    return Array.isArray(
+                        (candidate.getInitialModel() || {}).composition
+                    );
+                }
+            };
+        }
+
+        return CompositionModelPolicy;
+    }
+);

platform/containment/test/CompositionModelPolicySpec.js

@@ -0,0 +1,26 @@
+/*global define,Promise,describe,it,expect,beforeEach,waitsFor,jasmine*/
+
+define(
+    ["../src/CompositionModelPolicy"],
+    function (CompositionModelPolicy) {
+        "use strict";
+
+        describe("The composition model policy", function () {
+            var mockType,
+                policy;
+
+            beforeEach(function () {
+                mockType = jasmine.createSpyObj('type', ['getInitialModel']);
+                policy = new CompositionModelPolicy();
+            });
+
+            it("only allows composition for types which will have a composition property", function () {
+                mockType.getInitialModel.andReturn({});
+                expect(policy.allow(mockType)).toBeFalsy();
+                mockType.getInitialModel.andReturn({ composition: [] });
+                expect(policy.allow(mockType)).toBeTruthy();
+            });
+        });
+
+    }
+);

platform/containment/test/CompositionMutabilityPolicySpec.js

@@ -35,7 +35,7 @@ define(
                 policy = new CompositionMutabilityPolicy();
             });
 
-            it("only allows composition for types which will have a composition capability", function () {
+            it("only allows composition for types which can be created/modified", function () {
                 expect(policy.allow(mockType)).toBeFalsy();
                 mockType.hasFeature.andReturn(true);
                 expect(policy.allow(mockType)).toBeTruthy();

platform/containment/test/suite.json

@@ -1,6 +1,7 @@
 [
     "CapabilityTable",
     "ComposeActionPolicy",
+    "CompositionModelPolicy",
     "CompositionMutabilityPolicy",
     "CompositionPolicy",
     "ContainmentTable"