add patch/unpatch utility methods

tests/utils.test.ts

@@ -5,7 +5,9 @@ import {
   memoize,
   debounce,
   findInTree,
-  shallowEqual
+  shallowEqual,
+  patch,
+  unpatch
 } from "../src/utils";
 
 describe("escape", () => {
@@ -103,3 +105,56 @@ describe("shallowEqual", () => {
     expect(shallowEqual({ a: 1 }, ["a"])).toBe(false);
   });
 });
+
+describe("patch/unpatch", () => {
+  test("can monkey patch a class", () => {
+    class Test {
+      n = 1;
+
+      doSomething(): string {
+        return "hey";
+      }
+    }
+
+    patch(Test, "some_custo", {
+      doSomething(): string {
+        this.n = this.n + 1;
+        return this._super();
+      }
+    });
+
+    const t = new Test();
+    expect(t.n).toBe(1);
+    expect(t.doSomething()).toBe("hey");
+    expect(t.n).toBe(2);
+  });
+
+  test("cannot patch a class twice with same patch name", () => {
+    class Test {}
+
+    patch(Test, "some_custo", {});
+    expect(() => {
+      patch(Test, "some_custo", {});
+    }).toThrow();
+  });
+
+  test("can unpatch a class", () => {
+    class Test {
+      doSomething(): number {
+        return 1;
+      }
+    }
+
+    patch(Test, "some_custo", {
+      doSomething(): number {
+        return this._super() + 2;
+      }
+    });
+
+    const t = new Test();
+    expect(t.doSomething()).toBe(3);
+
+    unpatch(Test, "some_custo");
+    expect(t.doSomething()).toBe(1);
+  });
+});