Add Incorporate Existing Type Into Zod Schema as a Zod TIL

zod/incorporate-existing-type-into-zod-schema.md

@@ -0,0 +1,46 @@
+# Incorporate Existing Type Into Zod Schema
+
+Zod's API is great for quickly scaffolding the shape of data that we're
+working with. This breaks down when data has a more complex shape and is coming
+from somewhere else, like a Prisma client. The shape of the data, and types
+provided by the library, are determined somewhere else. We want to leverage
+that rather than redefine it.
+
+Fortunately, Zod has a way for us to incorporate an existing type into a Zod
+schema that we're building.
+
+```typescript
+import {z} from 'zod'
+import {Book} from '@prisma/client'
+
+const BookOrder = z.object({
+  customer: z.object({
+    email: z.string().email(),
+    name: z.string()
+  }),
+  books: // how do we use the `Book` type here?
+})
+```
+
+We can turn the `Book` type into a Zod type that we can use in our schema with
+`z.ZodType` and `z.any`.
+
+```typescript
+import {z} from 'zod'
+import {Book} from '@prisma/client'
+
+const BookSchema: z.ZodType<Book> = z.any()
+
+const BookOrder = z.object({
+  customer: z.object({
+    email: z.string().email(),
+    name: z.string()
+  }),
+  books: BookSchema.array()
+})
+```
+
+We create a `BookSchema` with `z.any` and then narrow it to a `z.ZodType` with
+our `Book` type.
+
+[source](https://github.com/colinhacks/zod/issues/52#issuecomment-629897855)