[FIX] app: support for arbitrary descriptors in env

Before this commit, when defining a getter in the env passed to the App,
the value was read, losing the definition of the property.

After this commit, declaring a getter in the env works as expected:
the property stays a getter.

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

@@ -1,5 +1,20 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`app App supports env with getters/setters 1`] = `
+"function anonymous(bdom, helpers
+) {
+  let { text, createBlock, list, multi, html, toggler, component, comment } = bdom;
+  
+  let block1 = createBlock(\`<div><block-text-0/> <block-text-1/></div>\`);
+  
+  return function template(ctx, node, key = \\"\\") {
+    let d1 = ctx['env'].someVal;
+    let d2 = Object.keys(ctx['env'].services);
+    return block1([d1, d2]);
+  }
+}"
+`;
+
 exports[`app destroy remove the widget from the DOM 1`] = `
 "function anonymous(bdom, helpers
 ) {

tests/components/app.test.ts

@@ -1,7 +1,7 @@
 import { App, Component } from "../../src";
 import { status } from "../../src/component/status";
 import { xml } from "../../src/tags";
-import { makeTestFixture, snapshotEverything } from "../helpers";
+import { makeTestFixture, snapshotEverything, nextTick } from "../helpers";
 
 let fixture: HTMLElement;
 
@@ -25,4 +25,30 @@ describe("app", () => {
     expect(document.contains(el)).toBe(false);
     expect(status(comp)).toBe("destroyed");
   });
+
+  test("App supports env with getters/setters", async () => {
+    let someVal = "maggot";
+
+    const services: any = { serv1: "" };
+    const env = {
+      get someVal() {
+        return someVal;
+      },
+      services,
+    };
+
+    class SomeComponent extends Component {
+      static template = xml`<div><t t-esc="env.someVal" /> <t t-esc="Object.keys(env.services)" /></div>`;
+    }
+
+    const app = new App(SomeComponent);
+    app.configure({ env });
+    const comp = await app.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>maggot serv1</div>");
+    someVal = "brain";
+    services.serv2 = "";
+    comp.render();
+    await nextTick();
+    expect(fixture.innerHTML).toBe("<div>brain serv1,serv2</div>");
+  });
 });