From 50d76e2fa3a057fbae009851a89d7a4b22309ee9 Mon Sep 17 00:00:00 2001
From: "Michael B. Gale" <mbg@github.com>
Date: Thu, 9 Jul 2026 23:42:28 +0100
Subject: [PATCH] Add an `object` `Validator`

---
 src/json/index.test.ts | 18 ++++++++++++++++++
 src/json/index.ts      | 10 ++++++++++
 2 files changed, 28 insertions(+)

diff --git a/src/json/index.test.ts b/src/json/index.test.ts
index a238d8071..71f800003 100644
--- a/src/json/index.test.ts
+++ b/src/json/index.test.ts
@@ -85,6 +85,24 @@ test("validateSchema - validates arrays", async (t) => {
   t.false(json.validateSchema(arraySchema, { arrayKey: [4, 8, 15, null] }));
 });
 
+const objectSchema = {
+  objectKey: json.object(arraySchema),
+};
+
+test("validateSchema - validates objects", async (t) => {
+  // Objects of the given schema are accepted.
+  t.true(json.validateSchema(objectSchema, { objectKey: { arrayKey: [] } }));
+  t.true(json.validateSchema(objectSchema, { objectKey: { arrayKey: [4] } }));
+
+  // Other values are not accepted.
+  t.false(json.validateSchema(objectSchema, {}));
+  t.false(json.validateSchema(objectSchema, { objectKey: [] }));
+  t.false(json.validateSchema(objectSchema, { objectKey: undefined }));
+  t.false(json.validateSchema(objectSchema, { objectKey: null }));
+  t.false(json.validateSchema(objectSchema, { objectKey: "foo" }));
+  t.false(json.validateSchema(objectSchema, { objectKey: 123 }));
+});
+
 test("validateSchema - checkSchema reports unknown keys", async (t) => {
   const result = json.checkSchema(testSchema, {
     requiredKey: "foo",
diff --git a/src/json/index.ts b/src/json/index.ts
index e9fbbd8a7..083bd49bb 100644
--- a/src/json/index.ts
+++ b/src/json/index.ts
@@ -76,6 +76,16 @@ export function array<T>(validator: Validator<T>) {
   } as const satisfies Validator<T[]>;
 }
 
+/** A validator for objects. */
+export function object(schema: Schema) {
+  return {
+    validate: (val: unknown) => {
+      return isObject(val) && validateSchema(schema, val);
+    },
+    required: true,
+  } as const satisfies Validator<FromSchema<typeof schema>>;
+}
+
 /**
  * Transforms a validator to be optional, accepting `undefined` or `null` for an
  * absent value.