From fd0fb5be008c69f2ca3a0fb6298543ec0ef39d3d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?G=C3=A9ry=20Debongnie?= <ged@odoo.com>
Date: Tue, 20 Aug 2019 15:34:13 +0200
Subject: [PATCH] [REF] observer: refactor observer using proxy

closes #253
---
 src/component/component.ts              |   4 +-
 src/core/observer.ts                    | 206 ++++----------
 src/store/connected_component.ts        |  29 +-
 src/store/store.ts                      |   3 +-
 tests/core/observer.test.ts             | 353 ++++++++++++++----------
 tests/store/connected_component.test.ts |  38 ++-
 tests/store/store.test.ts               |   5 +-
 tools/benchmarks/owl-master/app.js      |   3 +-
 8 files changed, 294 insertions(+), 347 deletions(-)

diff --git a/src/component/component.ts b/src/component/component.ts
index a53298a1..224f643f 100644
--- a/src/component/component.ts
+++ b/src/component/component.ts
@@ -506,7 +506,7 @@ export class Component<T extends Env, Props extends {}, State extends {}> {
     return this.__render(false, [], scope, vars);
   }
 
-  async __render(
+  __render(
     force: boolean = false,
     patchQueue: any[] = [],
     scope?: Object,
@@ -581,7 +581,7 @@ export class Component<T extends Env, Props extends {}, State extends {}> {
     if (this.state) {
       const __owl__ = this.__owl__;
       __owl__.observer = new Observer();
-      __owl__.observer.observe(this.state);
+      this.state = __owl__.observer.observe(this.state);
       __owl__.observer.notifyCB = this.render.bind(this);
     }
   }
diff --git a/src/core/observer.ts b/src/core/observer.ts
index 40d2a931..316c8c17 100644
--- a/src/core/observer.ts
+++ b/src/core/observer.ts
@@ -7,59 +7,13 @@
  * This is a Observer class that can observe any JS values.  The way it works
  * can be summarized thusly:
  * - primitive values are not observed at all
- * - Objects are observed by replacing all their keys with getters/setters
- *   (recursively)
- * - Arrays are observed by replacing their prototype with a customized version,
- *   which wrap some methods to allow the tracking of each state change.
+ * - Objects and arrays are observed by replacing them with a Proxy
+ * - each object/array metadata are tracked in a weakmap, and keep a revision
+ *   number
  *
- * Note that this code is inspired by Vue.
+ * Note that this code is loosely inspired by Vue.
  */
 
-//------------------------------------------------------------------------------
-// Modified Array prototype
-//------------------------------------------------------------------------------
-
-// we define here a new modified Array prototype, which basically override all
-// Array methods that change some state to be able to track their changes
-const methodsToPatch = ["push", "pop", "shift", "unshift", "splice", "sort", "reverse"];
-const methodLen = methodsToPatch.length;
-
-const ArrayProto = Array.prototype;
-const ModifiedArrayProto = Object.create(ArrayProto);
-
-for (let i = 0; i < methodLen; i++) {
-  const method = methodsToPatch[i];
-  const initialMethod = ArrayProto[method];
-  ModifiedArrayProto[method] = function(...args) {
-    if (!this.__observer__.allowMutations) {
-      throw new Error(`Array cannot be changed here")`);
-    }
-    this.__observer__.rev++;
-    this.__observer__.notifyChange();
-    this.__owl__.rev++;
-    let parent = this;
-    do {
-      parent.__owl__.deepRev++;
-    } while ((parent = parent.__owl__.parent));
-    let inserted;
-    switch (method) {
-      case "push":
-      case "unshift":
-        inserted = args;
-        break;
-      case "splice":
-        inserted = args.slice(2);
-        break;
-    }
-    if (inserted) {
-      for (let i = 0, iLen = inserted.length; i < iLen; i++) {
-        this.__observer__.observe(inserted[i], this);
-      }
-    }
-    return initialMethod.call(this, ...args);
-  };
-}
-
 //------------------------------------------------------------------------------
 // Observer
 //------------------------------------------------------------------------------
@@ -67,128 +21,90 @@ export class Observer {
   rev: number = 1;
   allowMutations: boolean = true;
   dirty: boolean = false;
-
-  static set(target: any, key: number | string, value: any) {
-    if (!target.__owl__) {
-      throw Error("`Observer.set()` can only be called with observed Objects or Arrays");
-    }
-    target.__owl__.observer.set(target, key, value);
-  }
-
-  static delete(target: any, key: number | string) {
-    if (!target.__owl__) {
-      throw Error("`Observer.delete()` can only be called with observed Objects");
-    }
-    target.__owl__.observer.delete(target, key);
-  }
+  weakMap: WeakMap<any, any> = new WeakMap();
 
   notifyCB() {}
-  notifyChange() {
+  async notifyChange() {
+
     this.dirty = true;
-    Promise.resolve().then(() => {
-      if (this.dirty) {
-        this.dirty = false;
-        this.notifyCB();
-      }
-    });
+    await Promise.resolve();
+    if (this.dirty) {
+      this.dirty = false;
+      this.notifyCB();
+    }
   }
 
-  observe(value: any, parent?: any) {
-    if (value === null) {
+  observe(value: any, parent?: any): any {
+    if (value === null || typeof value !== "object") {
       // fun fact: typeof null === 'object'
-      return;
-    }
-    if (typeof value !== "object") {
-      return;
-    }
-    if ("__owl__" in value) {
-      // already observed
-      value.__owl__.parent = parent;
-      return;
-    }
-    if (Array.isArray(value)) {
-      this._observeArr(value, parent);
-    } else {
-      this._observeObj(value, parent);
+      return value;
     }
+    let metadata = this.weakMap.get(value) || this._observe(value, parent);
+    return metadata.proxy;
   }
 
-  set(target: any, key: number | string, value: any) {
-    let alreadyDefined =
-      key in target && Object.getOwnPropertyDescriptor(target, key)!.configurable === false;
-    if (alreadyDefined) {
-      target[key] = value;
-    } else {
-      this._addProp(target, key, value);
-      this._updateRevNumber(target);
-    }
-    this.notifyChange();
+  revNumber(value): number {
+    const metadata = this.weakMap.get(value);
+    return metadata ? metadata.rev : 0;
+  }
+  deepRevNumber(value): number {
+    const metadata = this.weakMap.get(value);
+    return metadata ? metadata.deepRev : 0;
   }
 
-  delete(target: any, key: number | string) {
-    delete target[key];
-    this._updateRevNumber(target);
-    this.notifyChange();
-  }
-
-  _observeObj<T extends { __owl__?: any }>(obj: T, parent?: any) {
-    obj.__owl__ = {
-      rev: this.rev,
-      deepRev: this.rev,
-      parent,
-      observer: this
-    };
-    Object.defineProperty(obj, "__owl__", { enumerable: false });
-    for (let key in obj) {
-      this._addProp(obj, key, obj[key]);
-    }
-  }
-
-  _observeArr(arr: Array<any>, parent?: any) {
-    (<any>arr).__owl__ = {
-      rev: this.rev,
-      deepRev: this.rev,
-      parent,
-      observer: this
-    };
-    Object.defineProperty(arr, "__owl__", { enumerable: false });
-    (<any>arr).__proto__ = Object.create(ModifiedArrayProto);
-    (<any>arr).__proto__.__observer__ = this;
-    for (let i = 0, iLen = arr.length; i < iLen; i++) {
-      this.observe(arr[i], arr);
-    }
-  }
-
-  _addProp<T extends { __owl__?: any }>(obj: T, key: string | number, value: any) {
+  _observe(value, parent) {
     var self = this;
-    Object.defineProperty(obj, key, {
-      configurable: true,
-      enumerable: true,
-      get() {
-        return value;
+
+    const proxy = new Proxy(value, {
+      get(target, k) {
+        const targetValue = target[k];
+        return self.observe(targetValue, value);
       },
-      set(newVal) {
+      set(target, key: string, newVal): boolean {
+        const value = target[key];
         if (newVal !== value) {
           if (!self.allowMutations) {
             throw new Error(
               `Observed state cannot be changed here! (key: "${key}", val: "${newVal}")`
             );
           }
-          self._updateRevNumber(obj);
-          value = newVal;
-          self.observe(newVal, obj);
+          self._updateRevNumber(target);
+          target[key] = newVal;
           self.notifyChange();
         }
+        return true;
+      },
+      deleteProperty(target, key) {
+        if (key in target) {
+          delete target[key];
+          self._updateRevNumber(target);
+          self.notifyChange();
+        }
+        return true;
       }
     });
-    this.observe(value, obj);
+
+    const metadata = {
+      value,
+      proxy,
+      rev: this.rev,
+      deepRev: this.rev,
+      parent
+    };
+
+    this.weakMap.set(value, metadata);
+    this.weakMap.set(metadata.proxy, metadata);
+    return metadata;
   }
+
   _updateRevNumber(target: any) {
     this.rev++;
-    target.__owl__.rev!++;
+    let metadata = this.weakMap.get(target);
+    metadata.rev!++;
     let parent = target;
     do {
-      parent.__owl__.deepRev++;
-    } while ((parent = parent.__owl__.parent) && parent !== target);
+      metadata = this.weakMap.get(parent);
+      metadata.deepRev++;
+    } while ((parent = metadata.parent) && parent !== target);
   }
 }
diff --git a/src/store/connected_component.ts b/src/store/connected_component.ts
index 00ab3947..8033fc3f 100644
--- a/src/store/connected_component.ts
+++ b/src/store/connected_component.ts
@@ -4,20 +4,6 @@ import { Component, Env } from "../component/component";
 // Connect function
 //------------------------------------------------------------------------------
 
-function revNumber<T extends Object>(o: T): number {
-  if (o !== null && typeof o === "object" && (<any>o).__owl__) {
-    return (<any>o).__owl__.rev;
-  }
-  return 0;
-}
-
-function deepRevNumber<T extends Object>(o: T): number {
-  if (o !== null && typeof o === "object" && (<any>o).__owl__) {
-    return (<any>o).__owl__.deepRev;
-  }
-  return 0;
-}
-
 type HashFunction = (a: any, b: any) => number;
 
 export class ConnectedComponent<T extends Env, P, S> extends Component<T, P, S> {
@@ -27,15 +13,16 @@ export class ConnectedComponent<T extends Env, P, S> extends Component<T, P, S>
   }
 
   hashFunction: HashFunction = ({ storeProps }, options) => {
-    let refFunction = this.deep ? deepRevNumber : revNumber;
+    const observer = (this.__owl__ as any).store.observer;
+    let refFunction = this.deep ? observer.deepRevNumber : observer.revNumber;
     if ("__owl__" in storeProps) {
-      return refFunction(storeProps);
+      return refFunction.call(observer, storeProps);
     }
     const { currentStoreProps } = options;
     let hash = 0;
     for (let key in storeProps) {
       const val = storeProps[key];
-      const hashVal = refFunction(val);
+      const hashVal = refFunction.call(observer, val);
       if (hashVal === 0) {
         if (val !== currentStoreProps[key]) {
           options.didChange = true;
@@ -70,9 +57,7 @@ export class ConnectedComponent<T extends Env, P, S> extends Component<T, P, S>
     (<any>this.__owl__).storeHash = this.hashFunction(
       {
         state: store.state,
-        storeProps: storeProps,
-        revNumber,
-        deepRevNumber
+        storeProps: storeProps
       },
       {
         currentStoreProps: storeProps
@@ -109,9 +94,7 @@ export class ConnectedComponent<T extends Env, P, S> extends Component<T, P, S>
     const storeHash = this.hashFunction(
       {
         state: (<any>this.__owl__).store.state,
-        storeProps: storeProps,
-        revNumber,
-        deepRevNumber
+        storeProps: storeProps
       },
       options
     );
diff --git a/src/store/store.ts b/src/store/store.ts
index c5ba3f50..bce38e7f 100644
--- a/src/store/store.ts
+++ b/src/store/store.ts
@@ -53,14 +53,13 @@ export class Store extends EventBus {
   constructor(config: StoreConfig, options: StoreOption = {}) {
     super();
     this.debug = options.debug || false;
-    this.state = config.state || {};
     this.actions = config.actions;
     this.mutations = config.mutations;
     this.env = config.env;
     this.observer = new Observer();
     this.observer.notifyCB = this.__notifyComponents.bind(this);
     this.observer.allowMutations = false;
-    this.observer.observe(this.state);
+    this.state = this.observer.observe(config.state || {});
     this.getters = {};
     this._gettersCache = {};
 
diff --git a/tests/core/observer.test.ts b/tests/core/observer.test.ts
index 92defaab..9506d70b 100644
--- a/tests/core/observer.test.ts
+++ b/tests/core/observer.test.ts
@@ -4,307 +4,362 @@ import { nextMicroTick } from "../helpers";
 describe("observer", () => {
   test("properly observe objects", () => {
     const observer = new Observer();
-    const obj: any = {};
+    const obj: any = observer.observe({});
 
-    observer.observe(obj);
-    expect(obj.__owl__.rev).toBe(1);
+    expect(typeof obj).toBe("object");
+    expect(observer.revNumber(obj)).toBe(1);
+    expect(observer.deepRevNumber(obj)).toBe(1);
     expect(observer.rev).toBe(1);
 
-    const ob2: any = { a: 1 };
-    observer.observe(ob2);
-    expect(ob2.__owl__.rev).toBe(1);
-    ob2.a = 2;
-    expect(observer.rev).toBe(2);
-    expect(ob2.__owl__.rev).toBe(2);
+    const obj2: any = observer.observe({ a: 1 });
+    expect(observer.revNumber(obj2)).toBe(1);
+    expect(observer.revNumber(obj)).toBe(1);
+    expect(observer.deepRevNumber(obj)).toBe(1);
+    expect(observer.rev).toBe(1);
 
-    ob2.b = 3;
-    expect(observer.rev).toBe(2);
-    expect(ob2.__owl__.rev).toBe(2);
+    obj2.a = 2;
 
-    observer.set(ob2, "b", 4);
-    expect(observer.rev).toBe(3);
-    expect(ob2.__owl__.rev).toBe(3);
+    expect(observer.revNumber(obj)).toBe(1);
+    expect(observer.revNumber(obj2)).toBe(2);
+    expect(observer.rev).toBe(2);
+
+    expect(obj2).toEqual({
+      a: 2
+    });
   });
 
   test("properly handle null or undefined", () => {
     const observer = new Observer();
-    const obj: any = { a: null, b: undefined };
+    const obj: any = observer.observe({ a: null, b: undefined });
 
-    observer.observe(obj);
-    expect(obj.__owl__.rev).toBe(1);
+    expect(observer.revNumber(obj)).toBe(1);
+    expect(observer.deepRevNumber(obj)).toBe(1);
     expect(observer.rev).toBe(1);
 
     obj.a = 3;
-    expect(obj.__owl__.rev).toBe(2);
+    expect(observer.revNumber(obj)).toBe(2);
+    expect(observer.deepRevNumber(obj)).toBe(2);
+    expect(observer.rev).toBe(2);
 
     obj.b = 5;
-    expect(obj.__owl__.rev).toBe(3);
+    expect(observer.revNumber(obj)).toBe(3);
+    expect(observer.deepRevNumber(obj)).toBe(3);
+    expect(observer.rev).toBe(3);
 
     obj.a = null;
     obj.b = undefined;
-    expect(obj.__owl__.rev).toBe(5);
+    expect(observer.revNumber(obj)).toBe(5);
+    expect(observer.deepRevNumber(obj)).toBe(5);
+    expect(observer.rev).toBe(5);
+    expect(obj).toEqual({
+      a: null,
+      b: undefined
+    });
   });
 
   test("can change values in array", () => {
     const observer = new Observer();
-    const obj: any = { arr: [1, 2] };
+    const obj: any = observer.observe({ arr: [1, 2] });
 
-    observer.observe(obj);
-    expect(obj.arr.__owl__.rev).toBe(1);
+    expect(Array.isArray(obj.arr)).toBe(true);
+    expect(observer.revNumber(obj.arr)).toBe(1);
+    expect(observer.deepRevNumber(obj.arr)).toBe(1);
     expect(observer.rev).toBe(1);
 
     obj.arr[0] = "nope";
-    expect(obj.arr.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
-
-    observer.set(obj.arr, 0, "yep");
-    expect(obj.arr.__owl__.rev).toBe(2);
+    expect(observer.revNumber(obj.arr)).toBe(2);
+    expect(observer.deepRevNumber(obj.arr)).toBe(2);
+    expect(observer.revNumber(obj)).toBe(1);
+    expect(observer.deepRevNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
   });
 
   test("various object property changes", () => {
     const observer = new Observer();
-    const obj: any = { a: 1 };
-    observer.observe(obj);
-    expect(obj.__owl__.rev).toBe(1);
+    const obj: any = observer.observe({ a: 1 });
+
+    expect(observer.revNumber(obj)).toBe(1);
+    expect(observer.deepRevNumber(obj)).toBe(1);
+    expect(observer.rev).toBe(1);
+
     obj.a = 2;
+
+    expect(observer.revNumber(obj)).toBe(2);
+    expect(observer.deepRevNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
-    expect(obj.__owl__.rev).toBe(2);
 
     // same value again
     obj.a = 2;
+    expect(observer.revNumber(obj)).toBe(2);
+    expect(observer.deepRevNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
-    expect(obj.__owl__.rev).toBe(2);
 
     obj.a = 3;
+    expect(observer.revNumber(obj)).toBe(3);
+    expect(observer.deepRevNumber(obj)).toBe(3);
     expect(observer.rev).toBe(3);
-    expect(obj.__owl__.rev).toBe(3);
   });
 
   test("properly observe arrays", () => {
     const observer = new Observer();
-    const arr: any = [];
-    observer.observe(arr);
-    expect(arr.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
+    const arr: any = observer.observe([]);
+
+    expect(Array.isArray(arr)).toBe(true);
     expect(arr.length).toBe(0);
+    expect(observer.revNumber(arr)).toBe(1);
+    expect(observer.deepRevNumber(arr)).toBe(1);
+    expect(observer.rev).toBe(1);
 
     arr.push(1);
-    expect(arr.__owl__.rev).toBe(2);
+    expect(observer.revNumber(arr)).toBe(2);
+    expect(observer.deepRevNumber(arr)).toBe(2);
     expect(observer.rev).toBe(2);
     expect(arr.length).toBe(1);
+    expect(arr).toEqual([1]);
 
     arr.splice(1, 0, "hey");
-    expect(arr.__owl__.rev).toBe(3);
+    expect(observer.revNumber(arr)).toBe(3);
+    expect(observer.deepRevNumber(arr)).toBe(3);
     expect(observer.rev).toBe(3);
+    expect(arr).toEqual([1, "hey"]);
     expect(arr.length).toBe(2);
 
     arr.unshift("lindemans");
-    expect(arr.__owl__.rev).toBe(4);
+    //it generates 3 primitive operations
+    expect(observer.revNumber(arr)).toBe(6);
+    expect(observer.deepRevNumber(arr)).toBe(6);
+    expect(observer.rev).toBe(6);
+    expect(arr).toEqual(["lindemans", 1, "hey"]);
+    expect(arr.length).toBe(3);
 
     arr.reverse();
-    expect(arr.__owl__.rev).toBe(5);
+    //it generates 2 primitive operations
+    expect(observer.revNumber(arr)).toBe(8);
+    expect(observer.deepRevNumber(arr)).toBe(8);
+    expect(observer.rev).toBe(8);
+    expect(arr).toEqual(["hey", 1, "lindemans"]);
+    expect(arr.length).toBe(3);
 
-    arr.pop();
-    expect(arr.__owl__.rev).toBe(6);
-
-    arr.shift();
-    expect(arr.__owl__.rev).toBe(7);
-
-    arr.sort();
-    expect(arr.__owl__.rev).toBe(8);
+    arr.pop(); // one set, one delete
+    expect(observer.revNumber(arr)).toBe(10);
+    expect(observer.deepRevNumber(arr)).toBe(10);
+    expect(observer.rev).toBe(10);
+    expect(arr).toEqual(["hey", 1]);
+    expect(arr.length).toBe(2);
 
+    arr.shift(); // 2 sets, 1 delete
+    expect(observer.revNumber(arr)).toBe(13);
+    expect(observer.deepRevNumber(arr)).toBe(13);
+    expect(observer.rev).toBe(13);
     expect(arr).toEqual([1]);
+    expect(arr.length).toBe(1);
   });
 
   test("object pushed into arrays are observed", () => {
     const observer = new Observer();
-    const arr: any = [];
-    observer.observe(arr);
+    const arr: any = observer.observe([]);
     expect(observer.rev).toBe(1);
 
     arr.push({ kriek: 5 });
     expect(observer.rev).toBe(2);
-    expect(arr.__owl__.rev).toBe(2);
-    expect(arr[0].__owl__.rev).toBe(2);
+    expect(observer.revNumber(arr)).toBe(2);
+    expect(observer.revNumber(arr[0])).toBe(2);
 
     arr[0].kriek = 6;
+
     expect(observer.rev).toBe(3);
-    expect(arr.__owl__.rev).toBe(2);
-    expect(arr[0].__owl__.rev).toBe(3);
+    expect(observer.revNumber(arr)).toBe(2);
+    expect(observer.deepRevNumber(arr)).toBe(3);
+    expect(observer.revNumber(arr[0])).toBe(3);
   });
 
   test("set new property on observed object", async () => {
     const observer = new Observer();
     observer.notifyCB = jest.fn();
-    const state: any = { a: 1 };
-    observer.observe(state);
-    expect(state.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
+    const state: any = observer.observe({ a: 1 });
     expect(observer.notifyCB).toBeCalledTimes(0);
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state)).toBe(1);
+
+    state.b = 8;
 
-    Observer.set(state, "b", 8);
     await nextMicroTick();
-    expect(state.__owl__.rev).toBe(2);
-    expect(observer.rev).toBe(2);
+
     expect(observer.notifyCB).toBeCalledTimes(1);
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state)).toBe(2);
+
     expect(state.b).toBe(8);
   });
 
   test("delete property from observed object", async () => {
     const observer = new Observer();
     observer.notifyCB = jest.fn();
-    const state: any = { a: 1, b: 8 };
+    const state: any = observer.observe({ a: 1, b: 8 });
     observer.observe(state);
-    expect(state.__owl__.rev).toBe(1);
-    expect(observer.rev).toBe(1);
-    expect(observer.notifyCB).toBeCalledTimes(0);
 
-    Observer.delete(state, "b");
+    expect(observer.notifyCB).toBeCalledTimes(0);
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state)).toBe(1);
+
+    delete state.b;
     await nextMicroTick();
-    expect(state.__owl__.rev).toBe(2);
-    expect(observer.rev).toBe(2);
+
     expect(observer.notifyCB).toBeCalledTimes(1);
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state)).toBe(2);
+
     expect(state).toEqual({ a: 1 });
   });
 
   test("set element in observed array", async () => {
     const observer = new Observer();
     observer.notifyCB = jest.fn();
-    const state: any = ["a"];
-    observer.observe(state);
-    expect(state.__owl__.rev).toBe(1);
+    const state: any = observer.observe(["a"]);
+
     expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.deepRevNumber(state)).toBe(1);
     expect(observer.notifyCB).toBeCalledTimes(0);
 
-    Observer.set(state, 1, "b");
+    state[1] = "b";
+
     await nextMicroTick();
-    expect(state.__owl__.rev).toBe(2);
+
     expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state)).toBe(2);
+    expect(observer.deepRevNumber(state)).toBe(2);
     expect(observer.notifyCB).toBeCalledTimes(1);
+
     expect(state).toEqual(["a", "b"]);
   });
 
   test("properly observe arrays in object", () => {
     const observer = new Observer();
-    const state: any = { arr: [] };
-    observer.observe(state);
-    expect(state.arr.__owl__.rev).toBe(1);
+    const state: any = observer.observe({ arr: [] });
+
     expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state.arr)).toBe(1);
+    expect(observer.deepRevNumber(state.arr)).toBe(1);
     expect(state.arr.length).toBe(0);
 
     state.arr.push(1);
-    expect(state.arr.__owl__.rev).toBe(2);
     expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state.arr)).toBe(2);
+    expect(observer.deepRevNumber(state.arr)).toBe(2);
     expect(state.arr.length).toBe(1);
   });
 
   test("properly observe objects in array", () => {
     const observer = new Observer();
-    const state: any = { arr: [{ something: 1 }] };
+    const state: any = observer.observe({ arr: [{ something: 1 }] });
     observer.observe(state);
-    expect(state.arr.__owl__.rev).toBe(1);
-    expect(state.arr[0].__owl__.rev).toBe(1);
+
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state.arr)).toBe(1);
+    expect(observer.revNumber(state.arr[0])).toBe(1);
 
     state.arr[0].something = 2;
-    expect(state.arr.__owl__.rev).toBe(1);
-    expect(state.arr[0].__owl__.rev).toBe(2);
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state.arr)).toBe(1);
+    expect(observer.revNumber(state.arr[0])).toBe(2);
   });
 
   test("properly observe objects in object", () => {
     const observer = new Observer();
-    const state: any = { a: { b: 1 } };
-    observer.observe(state);
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.a.__owl__.rev).toBe(1);
+    const state: any = observer.observe({ a: { b: 1 } });
+
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.revNumber(state.a)).toBe(1);
 
     state.a.b = 2;
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.a.__owl__.rev).toBe(2);
+    expect(observer.rev).toBe(2);
+    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.revNumber(state.a)).toBe(2);
   });
 
   test("reobserve new object values", () => {
     const observer = new Observer();
-    const obj: any = { a: 1 };
-    observer.observe(obj);
-    expect(obj.__owl__.rev).toBe(1);
+    const obj: any = observer.observe({ a: 1 });
+
+    expect(observer.rev).toBe(1);
+    expect(observer.revNumber(obj)).toBe(1);
+
     obj.a = { b: 2 };
+
     expect(observer.rev).toBe(2);
-    expect(obj.__owl__.rev).toBe(2);
-
-    // we start at 2 because it is the new observer rev number
-    expect(obj.a.__owl__.rev).toBe(2);
-
+    expect(observer.revNumber(obj)).toBe(2);
+    expect(observer.revNumber(obj.a)).toBe(2);
     obj.a.b = 3;
     expect(observer.rev).toBe(3);
-    expect(obj.__owl__.rev).toBe(2);
-    expect(obj.a.__owl__.rev).toBe(3);
+    expect(observer.revNumber(obj)).toBe(2);
+    expect(observer.revNumber(obj.a)).toBe(3);
   });
 
   test("deep observe misc changes", () => {
     const observer = new Observer();
-    const state: any = { o: { a: 1 }, arr: [1], n: 13 };
-    observer.observe(state);
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.__owl__.deepRev).toBe(1);
+    const state: any = observer.observe({ o: { a: 1 }, arr: [1], n: 13 });
+    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.deepRevNumber(state)).toBe(1);
 
     state.o.a = 2;
     expect(observer.rev).toBe(2);
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.__owl__.deepRev).toBe(2);
+    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.deepRevNumber(state)).toBe(2);
 
     state.arr.push(2);
-    expect(state.__owl__.rev).toBe(1);
-    expect(state.__owl__.deepRev).toBe(3);
+    expect(observer.rev).toBe(3);
+    expect(observer.revNumber(state)).toBe(1);
+    expect(observer.deepRevNumber(state)).toBe(3);
 
     state.n = 155;
-    expect(state.__owl__.rev).toBe(2);
-    expect(state.__owl__.deepRev).toBe(4);
+    expect(observer.rev).toBe(4);
+    expect(observer.revNumber(state)).toBe(2);
+    expect(observer.deepRevNumber(state)).toBe(4);
   });
 
   test("properly handle already observed state", () => {
     const observer = new Observer();
-    const obj1: any = { a: 1 };
-    const obj2: any = { b: 1 };
-    observer.observe(obj1);
-    observer.observe(obj2);
-    expect(obj1.__owl__.rev).toBe(1);
-    expect(obj2.__owl__.rev).toBe(1);
+    const obj1: any = observer.observe({ a: 1 });
+    const obj2: any = observer.observe({ b: 1 });
+
+    expect(observer.revNumber(obj1)).toBe(1);
+    expect(observer.revNumber(obj2)).toBe(1);
 
     obj1.a = 2;
     obj2.b = 3;
-    expect(obj1.__owl__.rev).toBe(2);
-    expect(obj2.__owl__.rev).toBe(2);
+    expect(observer.revNumber(obj1)).toBe(2);
+    expect(observer.revNumber(obj2)).toBe(2);
 
     obj2.b = obj1;
-    expect(obj1.__owl__.rev).toBe(2);
-    expect(obj2.__owl__.rev).toBe(3);
+    expect(observer.revNumber(obj1)).toBe(2);
+    expect(observer.revNumber(obj2)).toBe(3);
   });
 
   test("can set a property more than once", () => {
     const observer = new Observer();
-    const obj: any = {};
+    const obj: any = observer.observe({});
 
-    observer.observe(obj);
-    expect(obj.__owl__.rev).toBe(1);
+    expect(observer.revNumber(obj)).toBe(1);
+    expect(observer.deepRevNumber(obj)).toBe(1);
     expect(observer.rev).toBe(1);
-    expect(obj.__owl__.deepRev).toBe(1);
 
-    observer.set(obj, "aku", "always finds annoying problems");
+    obj.aku = "always finds annoying problems";
+    expect(observer.revNumber(obj)).toBe(2);
+    expect(observer.deepRevNumber(obj)).toBe(2);
     expect(observer.rev).toBe(2);
-    expect(obj.__owl__.rev).toBe(2);
-    expect(obj.__owl__.deepRev).toBe(2);
 
-    observer.set(obj, "aku", "always finds good problems");
+    obj.aku = "always finds good problems";
+
+    expect(observer.revNumber(obj)).toBe(3);
+    expect(observer.deepRevNumber(obj)).toBe(3);
     expect(observer.rev).toBe(3);
-    expect(obj.__owl__.rev).toBe(3);
-    expect(obj.__owl__.deepRev).toBe(3);
   });
 
   test("properly handle swapping elements", () => {
     const observer = new Observer();
-    const obj: any = { a: { arr: [] }, b: 1 };
-    observer.observe(obj);
+    const obj: any = observer.observe({ a: { arr: [] }, b: 1 });
 
     // swap a and b
     const b = obj.b;
@@ -319,9 +374,9 @@ describe("observer", () => {
 
   test("properly handle assigning observed obj containing array", () => {
     const observer = new Observer();
-    const obj: any = { a: { arr: [], val: "test" } };
-    observer.observe(obj);
+    const obj: any = observer.observe({ a: { arr: [], val: "test" } });
 
+    expect(observer.rev).toBe(1);
     obj.a = { ...obj.a, val: "test2" };
     expect(observer.rev).toBe(2);
 
@@ -332,24 +387,25 @@ describe("observer", () => {
 
   test("accept cycles in observed state", () => {
     const observer = new Observer();
-    const obj1: any = {};
-    const obj2: any = { b: obj1, key: 1 };
+    let obj1: any = {};
+    let obj2: any = { b: obj1, key: 1 };
     obj1.a = obj2;
-    observer.observe(obj1);
-    expect(obj1.__owl__.rev).toBe(1);
-    expect(obj2.__owl__.rev).toBe(1);
+    obj1 = observer.observe(obj1);
+    obj2 = obj1.a;
+
+    expect(observer.revNumber(obj1)).toBe(1);
+    expect(observer.revNumber(obj2)).toBe(1);
 
     obj2.key = 3;
-    expect(obj1.__owl__.rev).toBe(1);
-    expect(obj2.__owl__.rev).toBe(2);
+    expect(observer.revNumber(obj1)).toBe(1);
+    expect(observer.revNumber(obj2)).toBe(2);
   });
 
   test("call callback when state is changed", async () => {
     const observer = new Observer();
     observer.notifyCB = jest.fn();
-    const obj: any = { a: 1, b: { c: 2 }, d: [{ e: 3 }], f: 4 };
+    const obj: any = observer.observe({ a: 1, b: { c: 2 }, d: [{ e: 3 }], f: 4 });
 
-    observer.observe(obj);
     expect(observer.notifyCB).toBeCalledTimes(0);
 
     obj.a = 2;
@@ -373,9 +429,7 @@ describe("observer", () => {
   test("throw error when state is mutated in object if allowMutation=false", async () => {
     const observer = new Observer();
     observer.allowMutations = false;
-    const obj: any = { a: 1 };
-    observer.observe(obj);
-
+    const obj: any = observer.observe({ a: 1 });
     expect(() => {
       obj.a = 2;
     }).toThrow('Observed state cannot be changed here! (key: "a", val: "2")');
@@ -384,11 +438,10 @@ describe("observer", () => {
   test("throw error when state is mutated in array if allowMutation=false", async () => {
     const observer = new Observer();
     observer.allowMutations = false;
-    const obj: any = { a: [1] };
-    observer.observe(obj);
+    const obj: any = observer.observe({ a: [1] });
 
     expect(() => {
       obj.a.push(2);
-    }).toThrow("Array cannot be changed here");
+    }).toThrow('Observed state cannot be changed here! (key: "1", val: "2")');
   });
 });
diff --git a/tests/store/connected_component.test.ts b/tests/store/connected_component.test.ts
index 106dcba8..dad0c20b 100644
--- a/tests/store/connected_component.test.ts
+++ b/tests/store/connected_component.test.ts
@@ -1,11 +1,8 @@
-import { core } from "../../src";
 import { Component, Env } from "../../src/component/component";
 import { ConnectedComponent } from "../../src/store/connected_component";
 import { Store } from "../../src/store/store";
 import { makeTestEnv, makeTestFixture, nextTick } from "../helpers";
 
-const Observer = core.Observer;
-
 describe("connecting a component to store", () => {
   let fixture: HTMLElement;
   let env: Env;
@@ -644,7 +641,7 @@ describe("connecting a component to store", () => {
   test("connected parent/children: no rendering if child is destroyed", async () => {
     const mutations = {
       removeTodo({ state }) {
-        Observer.delete(state.todos, 1);
+        delete state.todos[1];
       }
     };
     const todos = { 1: { id: 1, title: "kikoou" } };
@@ -760,7 +757,6 @@ describe("connecting a component to store", () => {
   });
 });
 
-
 describe("connected components and default values", () => {
   let fixture: HTMLElement;
   let env: Env;
@@ -795,7 +791,7 @@ describe("connected components and default values", () => {
     const app = new App(env);
 
     await app.mount(fixture);
-    expect(fixture.innerHTML).toBe('<div><div>Hello, John</div></div>');
+    expect(fixture.innerHTML).toBe("<div><div>Hello, John</div></div>");
   });
 
   test("can set default values", async () => {
@@ -819,13 +815,13 @@ describe("connected components and default values", () => {
     const app = new App(env);
 
     await app.mount(fixture);
-    expect(fixture.innerHTML).toBe('<div><div>Hello, John</div></div>');
+    expect(fixture.innerHTML).toBe("<div><div>Hello, John</div></div>");
 
     await app.__updateProps({ initialRecipient: "James" }, true);
-    expect(fixture.innerHTML).toBe('<div><div>Hello, James</div></div>');
+    expect(fixture.innerHTML).toBe("<div><div>Hello, James</div></div>");
 
     await app.__updateProps({ initialRecipient: undefined }, true);
-    expect(fixture.innerHTML).toBe('<div><div>Hello, John</div></div>');
+    expect(fixture.innerHTML).toBe("<div><div>Hello, John</div></div>");
   });
 
   test("can set default values (v2)", async () => {
@@ -846,9 +842,9 @@ describe("connected components and default values", () => {
 
     class Message extends ConnectedComponent<any, any, any> {
       static defaultProps = { showId: true };
-      static mapStoreToProps = function (state, ownProps) {
+      static mapStoreToProps = function(state, ownProps) {
         return {
-          message: state.messages[ownProps.messageId],
+          message: state.messages[ownProps.messageId]
         };
       };
     }
@@ -856,10 +852,10 @@ describe("connected components and default values", () => {
     class Thread extends ConnectedComponent<any, any, any> {
       components = { Message };
       static defaultProps = { showMessages: true };
-      static mapStoreToProps = function (state, ownProps) {
+      static mapStoreToProps = function(state, ownProps) {
         const thread = state.threads[ownProps.threadId];
         return {
-          thread,
+          thread
         };
       };
     }
@@ -872,11 +868,11 @@ describe("connected components and default values", () => {
     const state = {
       threads: {
         1: {
-          messages: [100, 101],
+          messages: [100, 101]
         },
         2: {
-          messages: [200],
-        },
+          messages: [200]
+        }
       },
       messages: {
         100: {
@@ -902,13 +898,15 @@ describe("connected components and default values", () => {
     const app = new App(env);
 
     await app.mount(fixture);
-    expect(fixture.innerHTML).toBe('<div><div><div>100Message100</div><div>101Message101</div></div></div>');
+    expect(fixture.innerHTML).toBe(
+      "<div><div><div>100Message100</div><div>101Message101</div></div></div>"
+    );
 
     await app.__updateProps({ threadId: 2 }, true);
-    expect(fixture.innerHTML).toBe('<div><div><div>200Message200</div></div></div>');
+    expect(fixture.innerHTML).toBe("<div><div><div>200Message200</div></div></div>");
 
-    store.commit('changeMessageContent', 200, "UpdatedMessage200");
+    store.commit("changeMessageContent", 200, "UpdatedMessage200");
     await nextTick();
-    expect(fixture.innerHTML).toBe('<div><div><div>200UpdatedMessage200</div></div></div>');
+    expect(fixture.innerHTML).toBe("<div><div><div>200UpdatedMessage200</div></div></div>");
   });
 });
diff --git a/tests/store/store.test.ts b/tests/store/store.test.ts
index 28f125f2..b83ff3c4 100644
--- a/tests/store/store.test.ts
+++ b/tests/store/store.test.ts
@@ -474,12 +474,11 @@ describe("basic use", () => {
 
 describe("advanced state properties", () => {
   test("state in the store is reference equal after mutation", async () => {
-    const state = {};
     const mutations = {
       donothing() {}
     };
-    const store = new Store({ state, mutations });
-    expect(store.state).toBe(state);
+    const store = new Store({ state:{}, mutations });
+    const state = store.state;
     store.commit("donothing");
     expect(store.state).toBe(state);
   });
diff --git a/tools/benchmarks/owl-master/app.js b/tools/benchmarks/owl-master/app.js
index 709d01ed..dd4f1cb6 100644
--- a/tools/benchmarks/owl-master/app.js
+++ b/tools/benchmarks/owl-master/app.js
@@ -107,12 +107,11 @@ class App extends owl.Component {
 
   updateSomeMessages() {
     this.benchmark("update every 10th", () => {
-      const setState = owl.core.Observer.set;
       const messages = this.state.messages;
       for (let i = 0; i < messages.length; i += 10) {
         const msg = Object.assign({}, messages[i]);
         msg.author += "!!!";
-        setState(messages, i, msg);
+        messages[i] = msg;
       }
     });
   }