[IMP] qweb: t-props directive

We reimplement the directive "t-props" and add some tests for it.

tests/components/t_props.test.ts

@@ -0,0 +1,54 @@
+import { Component, mount, useState, xml } from "../../src";
+import { makeTestFixture, nextTick, snapshotEverything } from "../helpers";
+
+snapshotEverything();
+
+let fixture: HTMLElement;
+
+beforeEach(() => {
+  fixture = makeTestFixture();
+});
+
+describe("t-props", () => {
+  test("t-props only", async () => {
+    class Comp extends Component {
+      static template = xml`<div><t t-esc="props.a"/></div>`;
+    }
+    class Parent extends Component {
+      static components = { Comp };
+      static template = xml`<div><div><Comp t-props="state"/></div></div>`;
+      state = useState({
+        a: "first",
+      });
+    }
+    const parent = await mount(Parent, fixture);
+    expect(fixture.textContent).toBe("first");
+    parent.state.a = "";
+    await nextTick();
+    expect(fixture.textContent).toBe("");
+    parent.state.a = "fixed";
+    await nextTick();
+    expect(fixture.textContent).toBe("fixed");
+  });
+
+  test("t-props and other props", async () => {
+    class Comp extends Component {
+      static template = xml`<div><t t-esc="props.a"/><t t-esc="props.b"/></div>`;
+    }
+    class Parent extends Component {
+      static components = { Comp };
+      static template = xml`<div><div><Comp t-props="state1" a="a"/></div></div>`;
+      state1 = useState({
+        a: "first",
+        b: "second",
+      });
+      a = "third";
+    }
+    const parent = await mount(Parent, fixture);
+    expect(fixture.textContent).toBe("thirdsecond");
+    delete parent.a;
+    parent.render();
+    await nextTick();
+    expect(fixture.textContent).toBe("second");
+  });
+});