Add object interceptor API to allow missing model and missing my-items handling (#3522)

* Extends Object API to allow adding interceptors

Co-authored-by: Andrew Henry <akhenry@gmail.com>

src/api/objects/InterceptorRegistry.js

@@ -0,0 +1,66 @@
+/*****************************************************************************
+ * Open MCT, Copyright (c) 2014-2020, United States Government
+ * as represented by the Administrator of the National Aeronautics and Space
+ * Administration. All rights reserved.
+ *
+ * Open MCT is licensed under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ * Open MCT includes source code licensed under additional open source
+ * licenses. See the Open Source Licenses file (LICENSES.md) included with
+ * this source code distribution or the Licensing information page available
+ * at runtime from the About dialog for additional information.
+ *****************************************************************************/
+export default class InterceptorRegistry {
+    /**
+     * A InterceptorRegistry maintains the definitions for different interceptors that may be invoked on domain objects.
+     * @interface InterceptorRegistry
+     * @memberof module:openmct
+     */
+    constructor() {
+        this.interceptors = [];
+    }
+
+    /**
+     * @interface InterceptorDef
+     * @property {function} appliesTo function that determines if this interceptor should be called for the given identifier/object
+     * @property {function} invoke function that transforms the provided domain object and returns the transformed domain object
+     * @property {function} priority the priority for this interceptor. A higher number returned has more weight than a lower number
+     * @memberof module:openmct InterceptorRegistry#
+     */
+
+    /**
+     * Register a new object interceptor.
+     *
+     * @param {module:openmct.InterceptorDef} interceptorDef the interceptor to add
+     * @method addInterceptor
+     * @memberof module:openmct.InterceptorRegistry#
+     */
+    addInterceptor(interceptorDef) {
+        //TODO: sort by priority
+        this.interceptors.push(interceptorDef);
+    }
+
+    /**
+     * Retrieve all interceptors applicable to a domain object.
+     * @method getInterceptors
+     * @returns [module:openmct.InterceptorDef] the registered interceptors for this identifier/object
+     * @memberof module:openmct.InterceptorRegistry#
+     */
+    getInterceptors(identifier, object) {
+        return this.interceptors.filter(interceptor => {
+            return typeof interceptor.appliesTo === 'function'
+                && interceptor.appliesTo(identifier, object);
+        });
+    }
+
+}
+

src/api/objects/ObjectAPI.js

@@ -26,6 +26,7 @@ define([
     './MutableObject',
     './RootRegistry',
     './RootObjectProvider',
+    './InterceptorRegistry',
     'EventEmitter'
 ], function (
     _,
@@ -33,6 +34,7 @@ define([
     MutableObject,
     RootRegistry,
     RootObjectProvider,
+    InterceptorRegistry,
     EventEmitter
 ) {
 
@@ -48,6 +50,7 @@ define([
         this.rootRegistry = new RootRegistry();
         this.rootProvider = new RootObjectProvider.default(this.rootRegistry);
         this.cache = {};
+        this.interceptorRegistry = new InterceptorRegistry.default();
     }
 
     /**
@@ -177,6 +180,10 @@ define([
 
         return objectPromise.then(result => {
             delete this.cache[keystring];
+            const interceptors = this.listGetInterceptors(identifier, result);
+            interceptors.forEach(interceptor => {
+                result = interceptor.invoke(identifier, result);
+            });
 
             return result;
         });
@@ -312,6 +319,27 @@ define([
         });
     };
 
+    /**
+     * Register an object interceptor that transforms a domain object requested via module:openmct.ObjectAPI.get
+     * The domain object will be transformed after it is retrieved from the persistence store
+     * The domain object will be transformed only if the interceptor is applicable to that domain object as defined by the InterceptorDef
+     *
+     * @param {module:openmct.InterceptorDef} interceptorDef the interceptor definition to add
+     * @method addGetInterceptor
+     * @memberof module:openmct.InterceptorRegistry#
+     */
+    ObjectAPI.prototype.addGetInterceptor = function (interceptorDef) {
+        this.interceptorRegistry.addInterceptor(interceptorDef);
+    };
+
+    /**
+     * Retrieve the interceptors for a given domain object.
+     * @private
+     */
+    ObjectAPI.prototype.listGetInterceptors = function (identifier, object) {
+        return this.interceptorRegistry.getInterceptors(identifier, object);
+    };
+
     /**
      * Uniquely identifies a domain object.
      *

src/api/objects/ObjectAPISpec.js

@@ -63,12 +63,51 @@ describe("The Object API", () => {
     describe("The get function", () => {
         describe("when a provider is available", () => {
             let mockProvider;
+            let mockInterceptor;
+            let anotherMockInterceptor;
+            let notApplicableMockInterceptor;
             beforeEach(() => {
                 mockProvider = jasmine.createSpyObj("mock provider", [
                     "get"
                 ]);
                 mockProvider.get.and.returnValue(Promise.resolve(mockDomainObject));
+
+                mockInterceptor = jasmine.createSpyObj("mock interceptor", [
+                    "appliesTo",
+                    "invoke"
+                ]);
+                mockInterceptor.appliesTo.and.returnValue(true);
+                mockInterceptor.invoke.and.callFake((identifier, object) => {
+                    return Object.assign({
+                        changed: true
+                    }, object);
+                });
+
+                anotherMockInterceptor = jasmine.createSpyObj("another mock interceptor", [
+                    "appliesTo",
+                    "invoke"
+                ]);
+                anotherMockInterceptor.appliesTo.and.returnValue(true);
+                anotherMockInterceptor.invoke.and.callFake((identifier, object) => {
+                    return Object.assign({
+                        alsoChanged: true
+                    }, object);
+                });
+
+                notApplicableMockInterceptor = jasmine.createSpyObj("not applicable mock interceptor", [
+                    "appliesTo",
+                    "invoke"
+                ]);
+                notApplicableMockInterceptor.appliesTo.and.returnValue(false);
+                notApplicableMockInterceptor.invoke.and.callFake((identifier, object) => {
+                    return Object.assign({
+                        shouldNotBeChanged: true
+                    }, object);
+                });
                 objectAPI.addProvider(TEST_NAMESPACE, mockProvider);
+                objectAPI.addGetInterceptor(mockInterceptor);
+                objectAPI.addGetInterceptor(anotherMockInterceptor);
+                objectAPI.addGetInterceptor(notApplicableMockInterceptor);
             });
 
             it("Caches multiple requests for the same object", () => {
@@ -78,6 +117,15 @@ describe("The Object API", () => {
                 objectAPI.get(mockDomainObject.identifier);
                 expect(mockProvider.get.calls.count()).toBe(1);
             });
+
+            it("applies any applicable interceptors", () => {
+                expect(mockDomainObject.changed).toBeUndefined();
+                objectAPI.get(mockDomainObject.identifier).then((object) => {
+                    expect(object.changed).toBeTrue();
+                    expect(object.alsoChanged).toBeTrue();
+                    expect(object.shouldNotBeChanged).toBeUndefined();
+                });
+            });
         });
     });
 });