[IMP] reactivity: add support for collections (Set/Map WeakSet/WeakMap)

src/reactivity.ts

@@ -7,9 +7,9 @@ const SKIP = Symbol("Skip");
 // Special key to subscribe to, to be notified of key creation/deletion
 const KEYCHANGES = Symbol("Key changes");
 
-type ObjectKey = string | number | symbol;
-
 type Target = object;
+type Collection = Set<any> | Map<any, any> | WeakMap<any, any>;
+type CollectionRawType = "Set" | "Map" | "WeakMap";
 
 export type Reactive<T extends Target = Target> = T & {
   [TARGET]: any;
@@ -18,8 +18,25 @@ export type Reactive<T extends Target = Target> = T & {
 export type NonReactive<T extends Target = Target> = T & {
   [SKIP]: any;
 };
-const objectToString = Object.prototype.toString;
 
+const objectToString = Object.prototype.toString;
+const objectHasOwnProperty = Object.prototype.hasOwnProperty;
+
+const SUPPORTED_RAW_TYPES = new Set(["Object", "Array", "Set", "Map", "WeakMap"]);
+const COLLECTION_RAWTYPES = new Set(["Set", "Map", "WeakMap"]);
+
+/**
+ * extract "RawType" from strings like "[object RawType]" => this lets us ignore
+ * many native objects such as Promise (whose toString is [object Promise])
+ * or Date ([object Date]), while also supporting collections without using
+ * instanceof in a loop
+ *
+ * @param obj the object to check
+ * @returns the raw type of the object
+ */
+function rawType(obj: any) {
+  return objectToString.call(obj).slice(8, -1);
+}
 /**
  * Checks whether a given value can be made into a reactive object.
  *
@@ -30,11 +47,17 @@ function canBeMadeReactive(value: any): boolean {
   if (typeof value !== "object") {
     return false;
   }
-  // extract "RawType" from strings like "[object RawType]" => this lets us
-  // ignore many native objects such as Promise (whose toString is [object Promise])
-  // or Date ([object Date]).
-  const rawType = objectToString.call(value).slice(8, -1);
-  return rawType === "Object" || rawType === "Array";
+  return SUPPORTED_RAW_TYPES.has(rawType(value));
+}
+/**
+ * Creates a reactive from the given object/callback if possible and returns it,
+ * returns the original object otherwise.
+ *
+ * @param value the value make reactive
+ * @returns a reactive for the given object when possible, the original otherwise
+ */
+function possiblyReactive(val: any, cb: Callback) {
+  return canBeMadeReactive(val) ? reactive(val, cb) : val;
 }
 
 /**
@@ -58,7 +81,7 @@ export function toRaw<T extends object>(value: Reactive<T>): T {
   return value[TARGET] || value;
 }
 
-const targetToKeysToCallbacks = new WeakMap<Target, Map<ObjectKey, Set<Callback>>>();
+const targetToKeysToCallbacks = new WeakMap<Target, Map<PropertyKey, Set<Callback>>>();
 /**
  * Observes a given key on a target with an callback. The callback will be
  * called when the given key changes on the target.
@@ -68,7 +91,7 @@ const targetToKeysToCallbacks = new WeakMap<Target, Map<ObjectKey, Set<Callback>
  *  or deletion)
  * @param callback the function to call when the key changes
  */
-function observeTargetKey(target: Target, key: ObjectKey, callback: Callback): void {
+function observeTargetKey(target: Target, key: PropertyKey, callback: Callback): void {
   if (!targetToKeysToCallbacks.get(target)) {
     targetToKeysToCallbacks.set(target, new Map());
   }
@@ -91,7 +114,7 @@ function observeTargetKey(target: Target, key: ObjectKey, callback: Callback): v
  * @param key the key that changed (or Symbol `KEYCHANGES` if a key was created
  *   or deleted)
  */
-function notifyReactives(target: Target, key: ObjectKey): void {
+function notifyReactives(target: Target, key: PropertyKey): void {
   const keyToCallbacks = targetToKeysToCallbacks.get(target);
   if (!keyToCallbacks) {
     return;
@@ -177,50 +200,218 @@ export function reactive<T extends Target>(
   }
   const reactivesForTarget = reactiveCache.get(target)!;
   if (!reactivesForTarget.has(callback)) {
-    const proxy = new Proxy(target, {
-      get(target: any, key: ObjectKey, proxy: Reactive<T>) {
-        if (key === TARGET) {
-          return target;
-        }
-        observeTargetKey(target, key, callback);
-        const value = Reflect.get(target, key, proxy);
-        if (!canBeMadeReactive(value)) {
-          return value;
-        }
-        return reactive(value, callback);
-      },
-      set(target, key, value, proxy) {
-        const isNewKey = !Object.hasOwnProperty.call(target, key);
-        const originalValue = Reflect.get(target, key, proxy);
-        const ret = Reflect.set(target, key, value, proxy);
-        if (isNewKey) {
-          notifyReactives(target, KEYCHANGES);
-        }
-        // While Array length may trigger the set trap, it's not actually set by this
-        // method but is updated behind the scenes, and the trap is not called with the
-        // new value. We disable the "same-value-optimization" for it because of that.
-        if (originalValue !== value || (Array.isArray(target) && key === "length")) {
-          notifyReactives(target, key);
-        }
-        return ret;
-      },
-      deleteProperty(target, key) {
-        const ret = Reflect.deleteProperty(target, key);
-        notifyReactives(target, KEYCHANGES);
-        notifyReactives(target, key);
-        return ret;
-      },
-      ownKeys(target) {
-        observeTargetKey(target, KEYCHANGES, callback);
-        return Reflect.ownKeys(target);
-      },
-      has(target, key) {
-        // TODO: this observes all key changes instead of only the presence of the argument key
-        observeTargetKey(target, KEYCHANGES, callback);
-        return Reflect.has(target, key);
-      },
-    });
+    const targetRawType = rawType(target);
+    const handler = COLLECTION_RAWTYPES.has(targetRawType)
+      ? collectionsProxyHandler(target as Collection, callback, targetRawType as CollectionRawType)
+      : basicProxyHandler<T>(callback);
+    const proxy = new Proxy(target, handler as ProxyHandler<T>) as Reactive<T>;
     reactivesForTarget.set(callback, proxy);
   }
   return reactivesForTarget.get(callback) as Reactive<T>;
 }
+/**
+ * Creates a basic proxy handler for regular objects and arrays.
+ *
+ * @param callback @see reactive
+ * @returns a proxy handler object
+ */
+function basicProxyHandler<T extends Target>(callback: Callback): ProxyHandler<T> {
+  return {
+    get(target: any, key: PropertyKey, proxy: Reactive<T>) {
+      if (key === TARGET) {
+        return target;
+      }
+      observeTargetKey(target, key, callback);
+      return possiblyReactive(Reflect.get(target, key, proxy), callback);
+    },
+    set(target, key, value, proxy) {
+      const isNewKey = !objectHasOwnProperty.call(target, key);
+      const originalValue = Reflect.get(target, key, proxy);
+      const ret = Reflect.set(target, key, value, proxy);
+      if (isNewKey) {
+        notifyReactives(target, KEYCHANGES);
+      }
+      // While Array length may trigger the set trap, it's not actually set by this
+      // method but is updated behind the scenes, and the trap is not called with the
+      // new value. We disable the "same-value-optimization" for it because of that.
+      if (originalValue !== value || (Array.isArray(target) && key === "length")) {
+        notifyReactives(target, key);
+      }
+      return ret;
+    },
+    deleteProperty(target, key) {
+      const ret = Reflect.deleteProperty(target, key);
+      // TODO: only notify when something was actually deleted
+      notifyReactives(target, KEYCHANGES);
+      notifyReactives(target, key);
+      return ret;
+    },
+    ownKeys(target) {
+      observeTargetKey(target, KEYCHANGES, callback);
+      return Reflect.ownKeys(target);
+    },
+    has(target, key) {
+      // TODO: this observes all key changes instead of only the presence of the argument key
+      // observing the key itself would observe value changes instead of presence changes
+      // so we may need a finer grained system to distinguish observing value vs presence.
+      observeTargetKey(target, KEYCHANGES, callback);
+      return Reflect.has(target, key);
+    },
+  } as ProxyHandler<T>;
+}
+/**
+ * Creates a function that will observe the key that is passed to it when called
+ * and delegates to the underlying method.
+ *
+ * @param methodName name of the method to delegate to
+ * @param target @see reactive
+ * @param callback @see reactive
+ */
+function makeKeyObserver(methodName: "has" | "get", target: any, callback: Callback) {
+  return (key: any) => {
+    key = toRaw(key);
+    observeTargetKey(target, key, callback);
+    return possiblyReactive(target[methodName](key), callback);
+  };
+}
+/**
+ * Creates an iterable that will delegate to the underlying iteration method and
+ * observe keys as necessary.
+ *
+ * @param methodName name of the method to delegate to
+ * @param target @see reactive
+ * @param callback @see reactive
+ */
+function makeIteratorObserver(
+  methodName: "keys" | "values" | "entries" | typeof Symbol.iterator,
+  target: any,
+  callback: Callback
+) {
+  return function* () {
+    observeTargetKey(target, KEYCHANGES, callback);
+    const keys = target.keys();
+    for (const item of target[methodName]()) {
+      const key = keys.next().value;
+      observeTargetKey(target, key, callback);
+      yield possiblyReactive(item, callback);
+    }
+  };
+}
+/**
+ * Creates a function that will delegate to an underlying method, and check if
+ * that method has modified the presence or value of a key, and notify the
+ * reactives appropriately.
+ *
+ * @param setterName name of the method to delegate to
+ * @param getterName name of the method which should be used to retrieve the
+ *  value before calling the delegate method for comparison purposes
+ * @param target @see reactive
+ */
+function delegateAndNotify(
+  setterName: "set" | "add" | "delete",
+  getterName: "has" | "get",
+  target: any
+) {
+  return (key: any, value: any) => {
+    key = toRaw(key);
+    const hadKey = target.has(key);
+    const originalValue = target[getterName](key);
+    const ret = target[setterName](key, value);
+    const hasKey = target.has(key);
+    if (hadKey !== hasKey) {
+      notifyReactives(target, KEYCHANGES);
+    }
+    if (originalValue !== value) {
+      notifyReactives(target, key);
+    }
+    return ret;
+  };
+}
+/**
+ * Creates a function that will clear the underlying collection and notify that
+ * the keys of the collection have changed.
+ *
+ * @param target @see reactive
+ */
+function makeClearNotifier(target: Map<any, any> | Set<any>) {
+  return () => {
+    const allKeys = [...target.keys()];
+    target.clear();
+    notifyReactives(target, KEYCHANGES);
+    for (const key of allKeys) {
+      notifyReactives(target, key);
+    }
+  };
+}
+/**
+ * Maps raw type of an object to an object containing functions that can be used
+ * to build an appropritate proxy handler for that raw type. Eg: when making a
+ * reactive set, calling the has method should mark the key that is being
+ * retrieved as observed, and calling the add or delete method should notify the
+ * reactives that the key which is being added or deleted has been modified.
+ */
+const rawTypeToFuncHandlers = {
+  Set: (target: any, callback: Callback) => ({
+    has: makeKeyObserver("has", target, callback),
+    add: delegateAndNotify("add", "has", target),
+    delete: delegateAndNotify("delete", "has", target),
+    keys: makeIteratorObserver("keys", target, callback),
+    values: makeIteratorObserver("values", target, callback),
+    entries: makeIteratorObserver("entries", target, callback),
+    [Symbol.iterator]: makeIteratorObserver(Symbol.iterator, target, callback),
+    clear: makeClearNotifier(target),
+    get size() {
+      observeTargetKey(target, KEYCHANGES, callback);
+      return target.size;
+    },
+  }),
+  Map: (target: any, callback: Callback) => ({
+    has: makeKeyObserver("has", target, callback),
+    get: makeKeyObserver("get", target, callback),
+    set: delegateAndNotify("set", "get", target),
+    delete: delegateAndNotify("delete", "has", target),
+    keys: makeIteratorObserver("keys", target, callback),
+    values: makeIteratorObserver("values", target, callback),
+    entries: makeIteratorObserver("entries", target, callback),
+    [Symbol.iterator]: makeIteratorObserver(Symbol.iterator, target, callback),
+    clear: makeClearNotifier(target),
+    get size() {
+      observeTargetKey(target, KEYCHANGES, callback);
+      return target.size;
+    },
+  }),
+  WeakMap: (target: any, callback: Callback) => ({
+    has: makeKeyObserver("has", target, callback),
+    get: makeKeyObserver("get", target, callback),
+    set: delegateAndNotify("set", "get", target),
+    delete: delegateAndNotify("delete", "has", target),
+  }),
+};
+/**
+ * Creates a proxy handler for collections (Set/Map/WeakMap)
+ *
+ * @param callback @see reactive
+ * @param target @see reactive
+ * @returns a proxy handler object
+ */
+function collectionsProxyHandler<T extends Collection>(
+  target: T,
+  callback: Callback,
+  targetRawType: CollectionRawType
+): ProxyHandler<T> {
+  // TODO: if performance is an issue we can create the special handlers lazily when each
+  // property is read.
+  const specialHandlers = rawTypeToFuncHandlers[targetRawType](target, callback);
+  return Object.assign(basicProxyHandler(callback), {
+    get(target: any, key: PropertyKey) {
+      if (key === TARGET) {
+        return target;
+      }
+      if (objectHasOwnProperty.call(specialHandlers, key)) {
+        return (specialHandlers as any)[key];
+      }
+      observeTargetKey(target, key, callback);
+      return possiblyReactive(target[key], callback);
+    },
+  }) as ProxyHandler<T>;
+}

tests/components/__snapshots__/reactivity.test.ts.snap

@@ -28,6 +28,20 @@ exports[`reactivity in lifecycle can use a state hook 2 1`] = `
 }"
 `;
 
+exports[`reactivity in lifecycle can use a state hook on Map 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  let block1 = createBlock(\`<div><block-text-0/></div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let txt1 = ctx['counter'].get('value');
+    return block1([txt1]);
+  }
+}"
+`;
+
 exports[`reactivity in lifecycle change state while mounting component 1`] = `
 "function anonymous(bdom, helpers
 ) {

tests/components/reactivity.test.ts

@@ -53,6 +53,18 @@ describe("reactivity in lifecycle", () => {
     expect(n).toBe(2); // no new rendering occured: b was never read via state!
   });
 
+  test("can use a state hook on Map", async () => {
+    class Counter extends Component {
+      static template = xml`<div><t t-esc="counter.get('value')"/></div>`;
+      counter = useState(new Map([["value", 42]]));
+    }
+    const counter = await mount(Counter, fixture);
+    expect(fixture.innerHTML).toBe("<div>42</div>");
+    counter.counter.set("value", 3);
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div>3</div>");
+  });
+
   test("state changes in willUnmount do not trigger rerender", async () => {
     const steps: string[] = [];
     class Child extends Component {

tests/reactivity.test.ts

@@ -171,6 +171,8 @@ describe("Reactivity", () => {
     expect(n).toBe(2);
   });
 
+  // Skipped because the hasOwnProperty trap is tripped by *writing*. We
+  // (probably) do not want to subscribe to changes on writes.
   test.skip("hasOwnProperty causes the key's presence to be observed", async () => {
     let n = 0;
     const state = createReactive({}, () => n++);
@@ -1093,18 +1095,482 @@ describe("Reactivity", () => {
     expect(n).toBe(1);
     expect(state.k).toEqual({ n: 2 });
   });
+});
 
-  test("can add collections set/weakset/map/weakmap in a reactive object", () => {
-    const rawSet = new Set();
-    const rawWeakSet = new WeakSet();
-    const rawMap = new Map();
-    const rawWeakMap = new WeakMap();
+describe("Collections", () => {
+  describe("Set", () => {
+    test("can make reactive Set", () => {
+      const set = new Set<number>();
+      const obj = reactive(set);
+      expect(obj).not.toBe(set);
+    });
 
-    const obj = reactive({ rawSet, rawWeakSet, rawMap, rawWeakMap });
-    expect(obj.rawSet).toBe(rawSet);
-    expect(obj.rawWeakSet).toBe(rawWeakSet);
-    expect(obj.rawMap).toBe(rawMap);
-    expect(obj.rawWeakMap).toBe(rawWeakMap);
+    test("can read", async () => {
+      const state = reactive(new Set([1]));
+      expect(state.has(1)).toBe(true);
+      expect(state.has(0)).toBe(false);
+    });
+
+    test("can add entries", () => {
+      const state = reactive(new Set());
+      state.add(1);
+      expect(state.has(1)).toBe(true);
+    });
+
+    test("can remove entries", () => {
+      const state = reactive(new Set([1]));
+      state.delete(1);
+      expect(state.has(1)).toBe(false);
+    });
+
+    test("can clear entries", () => {
+      const state = reactive(new Set([1]));
+      expect(state.size).toBe(1);
+      state.clear();
+      expect(state.size).toBe(0);
+    });
+
+    test("act like a Set", () => {
+      const state = reactive(new Set([1]));
+      expect([...state.entries()]).toEqual([[1, 1]]);
+      expect([...state.values()]).toEqual([1]);
+      expect([...state.keys()]).toEqual([1]);
+      expect([...state]).toEqual([1]); // Checks Symbol.iterator
+      expect(state.size).toBe(1);
+      expect(typeof state).toBe("object");
+      expect(state).toBeInstanceOf(Set);
+    });
+
+    test("reactive Set contains its keys", () => {
+      const state = reactive(new Set([{}]));
+      expect(state.has(state.keys().next().value)).toBe(true);
+    });
+
+    test("reactive Set contains its values", () => {
+      const state = reactive(new Set([{}]));
+      expect(state.has(state.values().next().value)).toBe(true);
+    });
+
+    test("reactive Set contains its entries' keys and values", () => {
+      const state = reactive(new Set([{}]));
+      const [key, val] = state.entries().next().value;
+      expect(state.has(key)).toBe(true);
+      expect(state.has(val)).toBe(true);
+    });
+
+    test("checking for a key subscribes the callback to changes to that key", () => {
+      const observer = jest.fn();
+      const state = reactive(new Set([1]), observer);
+
+      expect(state.has(2)).toBe(false); // subscribe to 2
+      expect(observer).toHaveBeenCalledTimes(0);
+      state.add(2);
+      expect(observer).toHaveBeenCalledTimes(1);
+      expect(state.has(2)).toBe(true); // subscribe to 2
+      state.delete(2);
+      expect(observer).toHaveBeenCalledTimes(2);
+      state.add(2);
+      expect(state.has(2)).toBe(true); // subscribe to 2
+      state.clear();
+      expect(observer).toHaveBeenCalledTimes(3);
+      expect(state.has(2)).toBe(false); // subscribe to 2
+      state.clear(); // clearing again doesn't notify again
+      expect(observer).toHaveBeenCalledTimes(3);
+
+      state.add(3); // setting unobserved key doesn't notify
+      expect(observer).toHaveBeenCalledTimes(3);
+    });
+
+    test("iterating on keys returns reactives", async () => {
+      const obj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new Set([obj]), observer);
+      const reactiveObj = state.keys().next().value;
+      expect(reactiveObj).not.toBe(obj);
+      expect(toRaw(reactiveObj as any)).toBe(obj);
+      reactiveObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveObj.a; // observe key "a" in sub-reactive;
+      reactiveObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveObj.a = 1; // setting same value again shouldn't notify
+      expect(observer).toHaveBeenCalledTimes(1);
+    });
+
+    test("iterating on values returns reactives", async () => {
+      const obj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new Set([obj]), observer);
+      const reactiveObj = state.values().next().value;
+      expect(reactiveObj).not.toBe(obj);
+      expect(toRaw(reactiveObj as any)).toBe(obj);
+      reactiveObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveObj.a; // observe key "a" in sub-reactive;
+      reactiveObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveObj.a = 1; // setting same value again shouldn't notify
+      expect(observer).toHaveBeenCalledTimes(1);
+    });
+
+    test("iterating on entries returns reactives", async () => {
+      const obj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new Set([obj]), observer);
+      const [reactiveObj, reactiveObj2] = state.entries().next().value;
+      expect(reactiveObj2).toBe(reactiveObj);
+      expect(reactiveObj).not.toBe(obj);
+      expect(toRaw(reactiveObj as any)).toBe(obj);
+      reactiveObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveObj.a; // observe key "a" in sub-reactive;
+      reactiveObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveObj.a = 1; // setting same value again shouldn't notify
+      expect(observer).toHaveBeenCalledTimes(1);
+    });
+
+    test("iterating on reactive Set returns reactives", async () => {
+      const obj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new Set([obj]), observer);
+      const reactiveObj = state[Symbol.iterator]().next().value;
+      expect(reactiveObj).not.toBe(obj);
+      expect(toRaw(reactiveObj as any)).toBe(obj);
+      reactiveObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveObj.a; // observe key "a" in sub-reactive;
+      reactiveObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveObj.a = 1; // setting same value again shouldn't notify
+      expect(observer).toHaveBeenCalledTimes(1);
+    });
+  });
+
+  describe("WeakSet", () => {
+    test("cannot make reactive WeakSet", () => {
+      const set = new WeakSet();
+      expect(() => reactive(set)).toThrowError("Cannot make the given value reactive");
+    });
+
+    test("WeakSet in reactive is original WeakSet", () => {
+      const obj = { set: new WeakSet() };
+      const state = reactive(obj);
+      expect(state.set).toBe(obj.set);
+    });
+  });
+
+  describe("Map", () => {
+    test("can make reactive Map", () => {
+      const map = new Map();
+      const obj = reactive(map);
+      expect(obj).not.toBe(map);
+    });
+
+    test("can read", async () => {
+      const state = reactive(new Map([[1, 0]]));
+      expect(state.has(1)).toBe(true);
+      expect(state.has(0)).toBe(false);
+      expect(state.get(1)).toBe(0);
+      expect(state.get(0)).toBeUndefined();
+    });
+
+    test("can add entries", () => {
+      const state = reactive(new Map());
+      state.set(1, 2);
+      expect(state.has(1)).toBe(true);
+      expect(state.get(1)).toBe(2);
+    });
+
+    test("can remove entries", () => {
+      const state = reactive(new Map([[1, 2]]));
+      state.delete(1);
+      expect(state.has(1)).toBe(false);
+      expect(state.get(1)).toBeUndefined();
+    });
+
+    test("can clear entries", () => {
+      const state = reactive(new Map([[1, 2]]));
+      expect(state.size).toBe(1);
+      state.clear();
+      expect(state.size).toBe(0);
+    });
+
+    test("act like a Map", () => {
+      const state = reactive(new Map([[1, 2]]));
+      expect([...state.entries()]).toEqual([[1, 2]]);
+      expect([...state.values()]).toEqual([2]);
+      expect([...state.keys()]).toEqual([1]);
+      expect([...state]).toEqual([[1, 2]]); // Checks Symbol.iterator
+      expect(state.size).toBe(1);
+      expect(typeof state).toBe("object");
+      expect(state).toBeInstanceOf(Map);
+    });
+
+    test("reactive Map contains its keys", () => {
+      const state = reactive(new Map([[{}, 1]]));
+      expect(state.has(state.keys().next().value)).toBe(true);
+    });
+
+    test("reactive Map values are equal to doing a get on the appropriate key", () => {
+      const state = reactive(new Map([[1, {}]]));
+      expect(state.get(1)).toBe(state.values().next().value);
+    });
+
+    test("reactive Map contains its entries' keys, and the associated value is the same as doing get", () => {
+      const state = reactive(new Map([[{}, {}]]));
+      const [key, val] = state.entries().next().value;
+      expect(state.has(key)).toBe(true);
+      expect(val).toBe(state.get(key));
+    });
+
+    test("checking for a key with 'has' subscribes the callback to changes to that key", () => {
+      const observer = jest.fn();
+      const state = reactive(new Map([[1, 2]]), observer);
+
+      expect(state.has(2)).toBe(false); // subscribe to 2
+      expect(observer).toHaveBeenCalledTimes(0);
+      state.set(2, 3);
+      expect(observer).toHaveBeenCalledTimes(1);
+      expect(state.has(2)).toBe(true); // subscribe to 2
+      state.delete(2);
+      expect(observer).toHaveBeenCalledTimes(2);
+      state.set(2, 3);
+      expect(state.has(2)).toBe(true); // subscribe to 2
+      state.clear();
+      expect(observer).toHaveBeenCalledTimes(3);
+      expect(state.has(2)).toBe(false); // subscribe to 2
+      state.clear(); // clearing again doesn't notify again
+      expect(observer).toHaveBeenCalledTimes(3);
+
+      state.set(3, 4); // setting unobserved key doesn't notify
+      expect(observer).toHaveBeenCalledTimes(3);
+    });
+
+    test("checking for a key with 'get' subscribes the callback to changes to that key", () => {
+      const observer = jest.fn();
+      const state = reactive(new Map([[1, 2]]), observer);
+
+      expect(state.get(2)).toBeUndefined(); // subscribe to 2
+      expect(observer).toHaveBeenCalledTimes(0);
+      state.set(2, 3);
+      expect(observer).toHaveBeenCalledTimes(1);
+      expect(state.get(2)).toBe(3); // subscribe to 2
+      state.delete(2);
+      expect(observer).toHaveBeenCalledTimes(2);
+      state.delete(2); // deleting again doesn't notify again
+      expect(observer).toHaveBeenCalledTimes(2);
+      state.set(2, 3);
+      expect(state.get(2)).toBe(3); // subscribe to 2
+      state.clear();
+      expect(observer).toHaveBeenCalledTimes(3);
+      expect(state.get(2)).toBeUndefined(); // subscribe to 2
+      state.clear(); // clearing again doesn't notify again
+      expect(observer).toHaveBeenCalledTimes(3);
+
+      state.set(3, 4); // setting unobserved key doesn't notify
+      expect(observer).toHaveBeenCalledTimes(3);
+    });
+
+    test("getting values returns a reactive", async () => {
+      const obj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new Map([[1, obj]]), observer);
+      const reactiveObj = state.get(1)!;
+      expect(reactiveObj).not.toBe(obj);
+      expect(toRaw(reactiveObj as any)).toBe(obj);
+      reactiveObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveObj.a; // observe key "a" in sub-reactive;
+      reactiveObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveObj.a = 1; // setting same value again shouldn't notify
+      expect(observer).toHaveBeenCalledTimes(1);
+    });
+
+    test("iterating on values returns reactives", async () => {
+      const obj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new Map([[1, obj]]), observer);
+      const reactiveObj = state.values().next().value;
+      expect(reactiveObj).not.toBe(obj);
+      expect(toRaw(reactiveObj as any)).toBe(obj);
+      reactiveObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveObj.a; // observe key "a" in sub-reactive;
+      reactiveObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveObj.a = 1; // setting same value again shouldn't notify
+      expect(observer).toHaveBeenCalledTimes(1);
+    });
+
+    test("iterating on keys returns reactives", async () => {
+      const obj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new Map([[obj, 1]]), observer);
+      const reactiveObj = state.keys().next().value;
+      expect(reactiveObj).not.toBe(obj);
+      expect(toRaw(reactiveObj as any)).toBe(obj);
+      reactiveObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveObj.a; // observe key "a" in sub-reactive;
+      reactiveObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveObj.a = 1; // setting same value again shouldn't notify
+      expect(observer).toHaveBeenCalledTimes(1);
+    });
+
+    test("iterating on reactive map returns reactives", async () => {
+      const keyObj = { a: 2 };
+      const valObj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new Map([[keyObj, valObj]]), observer);
+      const [reactiveKeyObj, reactiveValObj] = state[Symbol.iterator]().next().value;
+      expect(reactiveKeyObj).not.toBe(keyObj);
+      expect(reactiveValObj).not.toBe(valObj);
+      expect(toRaw(reactiveKeyObj as any)).toBe(keyObj);
+      expect(toRaw(reactiveValObj as any)).toBe(valObj);
+      reactiveKeyObj.a = 0;
+      reactiveValObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveKeyObj.a; // observe key "a" in key sub-reactive;
+      reactiveKeyObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveValObj.a; // observe key "a" in val sub-reactive;
+      reactiveValObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(2);
+      reactiveKeyObj.a = 1; // setting same value again shouldn't notify
+      reactiveValObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(2);
+    });
+
+    test("iterating on entries returns reactives", async () => {
+      const keyObj = { a: 2 };
+      const valObj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new Map([[keyObj, valObj]]), observer);
+      const [reactiveKeyObj, reactiveValObj] = state.entries().next().value;
+      expect(reactiveKeyObj).not.toBe(keyObj);
+      expect(reactiveValObj).not.toBe(valObj);
+      expect(toRaw(reactiveKeyObj as any)).toBe(keyObj);
+      expect(toRaw(reactiveValObj as any)).toBe(valObj);
+      reactiveKeyObj.a = 0;
+      reactiveValObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveKeyObj.a; // observe key "a" in key sub-reactive;
+      reactiveKeyObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveValObj.a; // observe key "a" in val sub-reactive;
+      reactiveValObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(2);
+      reactiveKeyObj.a = 1; // setting same value again shouldn't notify
+      reactiveValObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(2);
+    });
+  });
+
+  describe("WeakMap", () => {
+    test("can make reactive WeakMap", () => {
+      const map = new WeakMap();
+      const obj = reactive(map);
+      expect(obj).not.toBe(map);
+    });
+
+    test("can read", async () => {
+      const obj = {};
+      const obj2 = {};
+      const state = reactive(new WeakMap([[obj, 0]]));
+      expect(state.has(obj)).toBe(true);
+      expect(state.has(obj2)).toBe(false);
+      expect(state.get(obj)).toBe(0);
+      expect(state.get(obj2)).toBeUndefined();
+    });
+
+    test("can add entries", () => {
+      const obj = {};
+      const state = reactive(new WeakMap());
+      state.set(obj, 2);
+      expect(state.has(obj)).toBe(true);
+      expect(state.get(obj)).toBe(2);
+    });
+
+    test("can remove entries", () => {
+      const obj = {};
+      const state = reactive(new WeakMap([[obj, 2]]));
+      state.delete(obj);
+      expect(state.has(obj)).toBe(false);
+      expect(state.get(obj)).toBeUndefined();
+    });
+
+    test("act like a WeakMap", () => {
+      const obj = {};
+      const state = reactive(new WeakMap([[obj, 2]]));
+      expect(typeof state).toBe("object");
+      expect(state).toBeInstanceOf(WeakMap);
+    });
+
+    test("checking for a key with 'has' subscribes the callback to changes to that key", () => {
+      const observer = jest.fn();
+      const obj = {};
+      const obj2 = {};
+      const obj3 = {};
+      const state = reactive(new WeakMap([[obj2, 2]]), observer);
+
+      expect(state.has(obj)).toBe(false); // subscribe to obj
+      expect(observer).toHaveBeenCalledTimes(0);
+      state.set(obj, 3);
+      expect(observer).toHaveBeenCalledTimes(1);
+      expect(state.has(obj)).toBe(true); // subscribe to obj
+      state.delete(obj);
+      expect(observer).toHaveBeenCalledTimes(2);
+      state.set(obj, 3);
+      state.delete(obj);
+      expect(observer).toHaveBeenCalledTimes(2);
+      expect(state.has(obj)).toBe(false); // subscribe to obj
+
+      state.set(obj3, 4); // setting unobserved key doesn't notify
+      expect(observer).toHaveBeenCalledTimes(2);
+    });
+
+    test("checking for a key with 'get' subscribes the callback to changes to that key", () => {
+      const observer = jest.fn();
+      const obj = {};
+      const obj2 = {};
+      const obj3 = {};
+      const state = reactive(new WeakMap([[obj2, 2]]), observer);
+
+      expect(state.get(obj)).toBeUndefined(); // subscribe to obj
+      expect(observer).toHaveBeenCalledTimes(0);
+      state.set(obj, 3);
+      expect(observer).toHaveBeenCalledTimes(1);
+      expect(state.get(obj)).toBe(3); // subscribe to obj
+      state.delete(obj);
+      expect(observer).toHaveBeenCalledTimes(2);
+      state.set(obj, 3);
+      state.delete(obj);
+      expect(observer).toHaveBeenCalledTimes(2);
+      expect(state.get(obj)).toBeUndefined(); // subscribe to obj
+
+      state.set(obj3, 4); // setting unobserved key doesn't notify
+      expect(observer).toHaveBeenCalledTimes(2);
+    });
+
+    test("getting values returns a reactive", async () => {
+      const keyObj = {};
+      const valObj = { a: 2 };
+      const observer = jest.fn();
+      const state = reactive(new WeakMap([[keyObj, valObj]]), observer);
+      const reactiveObj = state.get(keyObj)!;
+      expect(reactiveObj).not.toBe(valObj);
+      expect(toRaw(reactiveObj as any)).toBe(valObj);
+      reactiveObj.a = 0;
+      expect(observer).toHaveBeenCalledTimes(0);
+      reactiveObj.a; // observe key "a" in sub-reactive;
+      reactiveObj.a = 1;
+      expect(observer).toHaveBeenCalledTimes(1);
+      reactiveObj.a = 1; // setting same value again shouldn't notify
+      expect(observer).toHaveBeenCalledTimes(1);
+    });
   });
 });