[FIX] observer: better handling of reassigning state

closes #50

src/observer.ts

@@ -73,6 +73,7 @@ export class Observer {
     }
     if ("__owl__" in value) {
       // already observed
+      value.__owl__.parent = parent;
       return;
     }
     if (Array.isArray(value)) {
@@ -88,12 +89,6 @@ export class Observer {
     this.notifyChange();
   }
 
-  unobserve(target: any) {
-    if (target !== null && typeof target === "object") {
-      delete target.__owl__;
-    }
-  }
-
   _observeObj<T extends { __owl__?: any }>(obj: T, parent?: any) {
     const keys = Object.keys(obj);
     obj.__owl__ = { rev: 1, deepRev: 1, parent };
@@ -131,14 +126,13 @@ export class Observer {
               `Observed state cannot be changed here! (key: "${key}", val: "${newVal}")`
             );
           }
-          self.unobserve(value);
           value = newVal;
           self.observe(newVal, obj);
           obj.__owl__.rev!++;
           let parent = obj;
           do {
             parent.__owl__.deepRev++;
-          } while ((parent = parent.__owl__.parent));
+          } while ((parent = parent.__owl__.parent) && parent !== obj);
           self.notifyChange();
         }
       }

tests/observer.test.ts

@@ -172,18 +172,6 @@ describe("observer", () => {
     expect(state.a.__owl__.rev).toBe(2);
   });
 
-  test("properly unobserve objects in object", () => {
-    const observer = new Observer();
-    const state: any = { a: { b: 1 } };
-    observer.observe(state);
-    expect(state.__owl__.rev).toBe(1);
-    const initialA = state.a;
-    expect(initialA.__owl__.rev).toBe(1);
-
-    state.a = "Karlsquell";
-    expect(initialA.__owl__).not.toBeDefined();
-  });
-
   test("reobserve new object values", () => {
     const observer = new Observer();
     const obj: any = { a: 1 };
@@ -240,6 +228,35 @@ describe("observer", () => {
     expect(obj2.__owl__.rev).toBe(3);
   });
 
+  test("properly handle swapping elements", () => {
+    const observer = new Observer();
+    const obj: any = { a: { arr: [] }, b: 1 };
+    observer.observe(obj);
+
+    // swap a and b
+    const b = obj.b;
+    obj.b = obj.a;
+    obj.a = b;
+    expect(observer.rev).toBe(3);
+
+    // push something into array to make sure it works
+    obj.b.arr.push("blanche");
+    expect(observer.rev).toBe(4);
+  });
+
+  test("properly handle assigning observed obj containing array", () => {
+    const observer = new Observer();
+    const obj: any = { a: { arr: [], val: "test" } };
+    observer.observe(obj);
+
+    obj.a = { ...obj.a, val: "test2" };
+    expect(observer.rev).toBe(2);
+
+    // push something into array to make sure it works
+    obj.a.arr.push("blanche");
+    expect(observer.rev).toBe(3);
+  });
+
   test("accept cycles in observed state", () => {
     const observer = new Observer();
     const obj1: any = {};