fix(proxy-observation): prevent proxies from being wrapped in proxies…

… again (#1716)

If you pass in a property that's part of a computed observation
structure into another class, the value is already wrapped in a proxy
before that property is observed in the new class. If that new class
then also uses computed observation, that property will be wrapped in a
proxy again, causing a "proxy within a proxy". This can repeat itself
endlessly, causing all sorts of issues.

Simply adding the proxy itself as the key to the `proxyMap` will solve
that problem at least as far as the issue in our app is concerned.

packages/__tests__/2-runtime/proxy-observable.spec.ts

@@ -31,6 +31,26 @@ describe('2-runtime/proxy-observable.spec.ts', function () {
     });
   }
 
+  it('does not rewrap a wrapped object', function () {
+    const proxied = ProxyObservable.wrap({});
+    assert.strictEqual(ProxyObservable.wrap(proxied), proxied);
+  });
+
+  it('does not rewrap a wrapped array', function () {
+    const proxied = ProxyObservable.wrap([]);
+    assert.strictEqual(ProxyObservable.wrap(proxied), proxied);
+  });
+
+  it('does not rewrap a wrapped map', function () {
+    const proxied = ProxyObservable.wrap(new Map());
+    assert.strictEqual(ProxyObservable.wrap(proxied), proxied);
+  });
+
+  it('does not rewrap a wrapped set', function () {
+    const proxied = ProxyObservable.wrap(new Set());
+    assert.strictEqual(ProxyObservable.wrap(proxied), proxied);
+  });
+
   it('does not wrap object that has been marked as "nowrap"', function () {
     @nowrap
     class MyModel { }

packages/runtime/src/observation/proxy-observation.ts

@@ -75,6 +75,7 @@ function createProxy<T extends object>(obj: T): T {
 
   const proxiedObj = new Proxy(obj, handler);
   proxyMap.set(obj, proxiedObj);
+  proxyMap.set(proxiedObj, proxiedObj);
 
   return proxiedObj as T;
 }