fix(core): Fix memory leak of resolve data from ALL transitions ever

The treeChanges object has references to the PathNodes from the previous transition (`.treeChanges("from")`).
The PathNode object has resolve data inside it.
The previous transition is reachable via a resolve (via tokens: `"$transition$"` or `Transition`).
Through this chain, all other transitions are reachable and not eligible for GC.

This change cleans out the previous Transition object from the resolves, but only
after a transition has been evicted from the `successfulTransitions` queue.
The `successfulTransitions` queue currently has a max size of 1, so the transition
is cleaned up once it is no longer the current nor previous transition
(it is cleaned when it's the previous previous transition);

Fixes ui-router#55
Fixes angular-ui/ui-router#3603
Fixes ui-router/angular#21

src/hooks/coreResolvables.ts

@@ -2,17 +2,42 @@
 import { Transition } from '../transition/transition';
 import { UIRouter } from '../router';
 import { TransitionService } from '../transition/transitionService';
+import { Resolvable } from '../resolve';
+import { extend, inArray, map, mapObj, unnestR, values } from '../common';
+import { PathNode } from '../path';
+import { TreeChanges } from "../transition";
 
 function addCoreResolvables(trans: Transition) {
-  trans.addResolvable({ token: UIRouter,       deps: [], resolveFn: () => trans.router,   data: trans.router },   '');
-  trans.addResolvable({ token: Transition,     deps: [], resolveFn: () => trans,          data: trans },          '');
-  trans.addResolvable({ token: '$transition$', deps: [], resolveFn: () => trans,          data: trans },          '');
-  trans.addResolvable({ token: '$stateParams', deps: [], resolveFn: () => trans.params(), data: trans.params() }, '');
+  trans.addResolvable(Resolvable.fromData(UIRouter, trans.router), '');
+  trans.addResolvable(Resolvable.fromData(Transition, trans), '');
+  trans.addResolvable(Resolvable.fromData('$transition$', trans), '');
+  trans.addResolvable(Resolvable.fromData('$stateParams', trans.params()), '');
 
   trans.entering().forEach(state => {
-    trans.addResolvable({ token: '$state$',    deps: [], resolveFn: () => state,          data: state },       state);
+    trans.addResolvable(Resolvable.fromData('$state$', state), state);
   });
 }
 
 export const registerAddCoreResolvables = (transitionService: TransitionService) =>
     transitionService.onCreate({}, addCoreResolvables);
+
+const TRANSITION_TOKENS = ['$transition$', Transition];
+const isTransition = inArray(TRANSITION_TOKENS);
+
+// References to Transition in the treeChanges pathnodes makes all
+// previous Transitions reachable in memory, causing a memory leak
+// This function removes resolves for '$transition$' and `Transition` from the treeChanges.
+// Do not use this on current transitions, only on old ones.
+export const treeChangesCleanup = (trans: Transition) => {
+  // If the resolvable is a Transition, return a new resolvable with null data
+  const replaceTransitionWithNull = (r: Resolvable): Resolvable =>
+    isTransition(r.token) ? Resolvable.fromData(r.token, null) : r;
+
+  const cleanPath = (path: PathNode[]) => path.map((node: PathNode) => {
+    const resolvables = node.resolvables.map(replaceTransitionWithNull);
+    return extend(node.clone(), { resolvables });
+  });
+
+  const treeChanges: TreeChanges = trans.treeChanges();
+  mapObj(treeChanges, cleanPath, treeChanges);
+};

src/resolve/resolvable.ts

@@ -88,7 +88,7 @@ export class Resolvable implements ResolvableLiteral {
       this.data = data;
       this.resolved = data !== undefined;
       this.promise = this.resolved ? services.$q.when(this.data) : undefined;
-    } else if (isObject(arg1) && arg1.token && isFunction(arg1.resolveFn)) {
+    } else if (isObject(arg1) && arg1.token && (arg1.hasOwnProperty('resolveFn') || arg1.hasOwnProperty('data'))) {
       const literal = <ResolvableLiteral> arg1;
       return new Resolvable(literal.token, literal.resolveFn, literal.deps, literal.policy, literal.data);
     }
@@ -144,6 +144,7 @@ export class Resolvable implements ResolvableLiteral {
     const applyResolvedValue = (resolvedValue: any) => {
       this.data = resolvedValue;
       this.resolved = true;
+      this.resolveFn = null;
       trace.traceResolvableResolved(this, trans);
       return this.data;
     };

src/router.ts

@@ -45,12 +45,12 @@ export class UIRouter {
   /** Provides services related to ui-view synchronization */
   viewService = new ViewService();
 
-  /** Provides services related to Transitions */
-  transitionService: TransitionService = new TransitionService(this);
-
   /** Global router state */
   globals: UIRouterGlobals = new UIRouterGlobals();
 
+  /** Provides services related to Transitions */
+  transitionService: TransitionService = new TransitionService(this);
+
   /**
    * Deprecated for public use. Use [[urlService]] instead.
    * @deprecated Use [[urlService]] instead

src/transition/hookRegistry.ts

@@ -2,18 +2,14 @@
  * @coreapi
  * @module transition
  */ /** for typedoc */
-import { extend, removeFrom, tail, values, identity, map } from '../common/common';
-import { isString, isFunction } from '../common/predicates';
+import { isString, isFunction, Glob, extend, removeFrom, tail, values, identity, mapObj } from '../common';
 import { PathNode } from '../path/pathNode';
 import {
-    TransitionStateHookFn, TransitionHookFn, TransitionHookPhase, TransitionHookScope, IHookRegistry, PathType,
-} from './interface'; // has or is using
-
-import {
-    HookRegOptions, HookMatchCriteria, TreeChanges,
-    HookMatchCriterion, IMatchingNodes, HookFn,
+  TransitionStateHookFn, TransitionHookFn, TransitionHookPhase, // has or is using
+  TransitionHookScope, IHookRegistry, PathType,
 } from './interface';
-import { Glob } from '../common/glob';
+
+import { HookRegOptions, HookMatchCriteria, TreeChanges, HookMatchCriterion, IMatchingNodes, HookFn } from './interface';
 import { StateObject } from '../state/stateObject';
 import { TransitionEventType } from './transitionEventType';
 import { TransitionService } from './transitionService';
@@ -108,7 +104,7 @@ export class RegisteredHook {
    * }
    */
   private _getDefaultMatchCriteria(): HookMatchCriteria {
-    return map(this.tranSvc._pluginapi._getPathTypes(), () => true);
+    return mapObj(this.tranSvc._pluginapi._getPathTypes(), () => true);
   }
 
   /**

src/transition/transitionService.ts

@@ -13,7 +13,7 @@ import { TargetState } from '../state/targetState';
 import { PathNode } from '../path/pathNode';
 import { ViewService } from '../view/view';
 import { UIRouter } from '../router';
-import { registerAddCoreResolvables } from '../hooks/coreResolvables';
+import { registerAddCoreResolvables, treeChangesCleanup } from '../hooks/coreResolvables';
 import { registerRedirectToHook } from '../hooks/redirectTo';
 import { registerOnExitHook, registerOnRetainHook, registerOnEnterHook } from '../hooks/onEnterExitRetain';
 import { registerEagerResolvePath, registerLazyResolveState, registerResolveRemaining } from '../hooks/resolve';
@@ -163,6 +163,7 @@ export class TransitionService implements IHookRegistry, Disposable {
     this._defineCorePaths();
     this._defineCoreEvents();
     this._registerCoreTransitionHooks();
+    _router.globals.successfulTransitions.onEvict(treeChangesCleanup);
   }
 
   /**

test/transitionSpec.ts

@@ -1002,4 +1002,22 @@ describe('transition', function () {
       done();
     });
   });
+
+  describe('from previous transitions', () => {
+    it('should get their Transition resolves cleaned up', async(done) => {
+      router.stateRegistry.register({ name: 'resolve', resolve: { foo: () => 'Some data' } });
+      const trans = router.stateService.go('resolve').transition;
+      await trans.promise;
+
+      expect(trans.injector().get(Transition)).toBe(trans);
+      expect(trans.injector().get('foo')).toBe('Some data');
+
+      await router.stateService.go('A');
+
+      expect(trans.injector().get(Transition)).toBe(null);
+      expect(trans.injector().get('foo')).toBe('Some data');
+
+      done();
+    });
+  });
 });