Added overriding example

Author: mattpocock

src/05-external-libraries/26.5-declaration-solution.d.ts

@@ -0,0 +1,6 @@
+declare module "fake-animation-lib-solution" {
+  export function getAnimatingState():
+    | "before-animation"
+    | "animating"
+    | "after-animation";
+}

src/05-external-libraries/26.5-override-external-lib-types.problem.ts

@@ -1,3 +1,13 @@
-// TODO
+import { getAnimatingState } from "../fake-animation-lib";
+import { Equal, Expect } from "../helpers/type-utils";
 
-export {};
+const animatingState = getAnimatingState();
+
+type tests = [
+  Expect<
+    Equal<
+      typeof animatingState,
+      "before-animation" | "animating" | "after-animation"
+    >
+  >,
+];

src/05-external-libraries/26.5-override-external-lib-types.solution.ts

@@ -0,0 +1,13 @@
+import { getAnimatingState } from "fake-animation-lib-solution";
+import { Equal, Expect } from "../helpers/type-utils";
+
+const animatingState = getAnimatingState();
+
+type tests = [
+  Expect<
+    Equal<
+      typeof animatingState,
+      "before-animation" | "animating" | "after-animation"
+    >
+  >,
+];

src/fake-animation-lib/index.ts

@@ -0,0 +1,11 @@
+export const getAnimatingState = (): string => {
+  if (Math.random() > 0.5) {
+    return "before-animation";
+  }
+
+  if (Math.random() > 0.5) {
+    return "animating";
+  }
+
+  return "after-animation";
+};

tsconfig.json

@@ -33,6 +33,12 @@
     "paths": {
       "fake-external-lib": [
         "./src/fake-external-lib/index"
+      ],
+      "fake-animation-lib": [
+        "./src/fake-animation-lib/index"
+      ],
+      "fake-animation-lib-solution": [
+        "./src/fake-animation-lib/index"
       ]
     }, /* Specify a set of entries that re-map imports to additional lookup locations. */
     // "rootDirs": [],                                   /* Allow multiple folders to be treated as one when resolving modules. */