Add Set Custom Error Message For Nonempty Array as a Zod TIL

zod/set-custom-error-message-for-nonempty-array.md

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+# Set Custom Error Message For Nonempty Array
+
+Let's say we have the following schema that represents a team:
+
+```typescript
+const TeamSchema = z.object({
+  name: z.string(),
+  members: z.array(
+    z.object({ firstName: z.string(), lastName: z.string() })
+  )
+})
+```
+
+If we want to enforce that a team must contain at least _one_ member in order
+to be valid, we can chain the `nonempty` function on the `members` array.
+
+```typescript
+const TeamSchema = z.object({
+  name: z.string(),
+  members: z.array(
+    z.object({ firstName: z.string(), lastName: z.string() })
+  ).nonempty()
+})
+```
+
+Then we can set a custom error message for when that _nonempty_ requirement is
+violated by adding an object argument with a `message`:
+
+```typescript
+const TeamSchema = z.object({
+  name: z.string(),
+  members: z.array(
+    z.object({ firstName: z.string(), lastName: z.string() })
+  ).nonempty({
+    message: 'A team must contain at least one member'
+  })
+})
+```
+
+Here is that schema in action, not the `message` in the error:
+
+```typescript
+TeamSchema.parse({ name: 'A-Team', members: [] })
+// Error: [{
+//   "code": "too_small",
+//   "minimum": 1,
+//   "type": "array",
+//   "inclusive": true,
+//   "exact": false,
+//   "message": "A team must contain at least one member",
+//   "path": [
+//     "members"
+//   ]
+// }]
+```
+
+[source](https://github.com/colinhacks/zod#nonempty)