From b1c50597088c2e4e1d3666f53f3f9de171cbd506 Mon Sep 17 00:00:00 2001
From: Yusuke Wada <yusuke@kamawada.com>
Date: Thu, 2 Mar 2023 08:56:13 +0900
Subject: [PATCH] feat(`jsonT`): check JSON type (#939)

* feat(`jsonT`): check JSON type

* denoify

* use `JSONValue`

* create `TrueAndFalseToBoolean` and add a comment
---
 deno_dist/context.ts      | 10 ++++++----
 deno_dist/utils/types.ts  | 18 ++++++++++++++++++
 src/client/client.test.ts | 11 +++++++++++
 src/context.ts            | 10 ++++++----
 src/utils/types.ts        | 18 ++++++++++++++++++
 5 files changed, 59 insertions(+), 8 deletions(-)

diff --git a/deno_dist/context.ts b/deno_dist/context.ts
index cc84d7d4..876accf2 100644
--- a/deno_dist/context.ts
+++ b/deno_dist/context.ts
@@ -4,6 +4,7 @@ import type { Env, NotFoundHandler, Input } from './types.ts'
 import type { CookieOptions } from './utils/cookie.ts'
 import { serialize } from './utils/cookie.ts'
 import type { StatusCode } from './utils/http-status.ts'
+import type { PrettyJSON, JSONValue } from './utils/types.ts'
 
 type Runtime = 'node' | 'deno' | 'bun' | 'workerd' | 'fastly' | 'edge-light' | 'lagon' | 'other'
 type HeaderRecord = Record<string, string | string[]>
@@ -237,14 +238,15 @@ export class Context<
     return this.newResponse(body, status, headers)
   }
 
-  jsonT = <T = object>(
-    object: T,
+  jsonT = <T>(
+    object: T extends JSONValue ? T : JSONValue,
     status: StatusCode = this._status,
     headers?: HeaderRecord
-  ): TypedResponse<T> => {
+  ): TypedResponse<T extends JSONValue ? (JSONValue extends T ? never : PrettyJSON<T>) : never> => {
     return {
       response: this.json(object, status, headers),
-      data: object,
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      data: object as any,
       format: 'json',
     }
   }
diff --git a/deno_dist/utils/types.ts b/deno_dist/utils/types.ts
index 20057566..38b8e25f 100644
--- a/deno_dist/utils/types.ts
+++ b/deno_dist/utils/types.ts
@@ -10,3 +10,21 @@ export type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) ex
 ) => void
   ? I
   : never
+
+export type JSONPrimitive = string | boolean | number | null | undefined
+export type JSONArray = (JSONPrimitive | JSONObject | JSONArray)[]
+export type JSONObject = { [key: string]: JSONPrimitive | JSONArray | JSONObject }
+export type JSONValue = JSONObject | JSONArray | JSONPrimitive
+
+// `boolean` will be `true` or `false` because it's an alias of them.
+// See: https://github.com/microsoft/TypeScript/issues/22596
+// This type converts `true | false` to `boolean` that we expect.
+type TrueAndFalseToBoolean<T> = T extends true ? boolean : T extends false ? boolean : T
+
+export type PrettyJSON<T> = T extends JSONPrimitive
+  ? TrueAndFalseToBoolean<T>
+  : T extends JSONArray
+  ? PrettyJSON<T[number]>
+  : T extends JSONObject
+  ? { [K in keyof T]: PrettyJSON<T[K]> }
+  : never
diff --git a/src/client/client.test.ts b/src/client/client.test.ts
index 13db0017..cd39ff30 100644
--- a/src/client/client.test.ts
+++ b/src/client/client.test.ts
@@ -332,6 +332,17 @@ describe('Merge path with `app.route()`', () => {
     expect(data.ok).toBe(true)
   })
 
+  it('Should not allow the incorrect JSON type', async () => {
+    const app = new Hono()
+    // @ts-ignore
+    const route = app.get('/api/foo', (c) => c.jsonT({ datetime: new Date() }))
+    type AppType = typeof route
+    const client = hc<AppType>('http://localhost')
+    const res = await client.api.foo.$get()
+    const data = await res.json()
+    type verify = Expect<Equal<never, typeof data>>
+  })
+
   describe('Multiple endpoints', () => {
     const api = new Hono()
       .get('/foo', (c) => c.jsonT({ foo: '' }))
diff --git a/src/context.ts b/src/context.ts
index 922e94fe..a928f04c 100644
--- a/src/context.ts
+++ b/src/context.ts
@@ -4,6 +4,7 @@ import type { Env, NotFoundHandler, Input } from './types'
 import type { CookieOptions } from './utils/cookie'
 import { serialize } from './utils/cookie'
 import type { StatusCode } from './utils/http-status'
+import type { PrettyJSON, JSONValue } from './utils/types'
 
 type Runtime = 'node' | 'deno' | 'bun' | 'workerd' | 'fastly' | 'edge-light' | 'lagon' | 'other'
 type HeaderRecord = Record<string, string | string[]>
@@ -237,14 +238,15 @@ export class Context<
     return this.newResponse(body, status, headers)
   }
 
-  jsonT = <T = object>(
-    object: T,
+  jsonT = <T>(
+    object: T extends JSONValue ? T : JSONValue,
     status: StatusCode = this._status,
     headers?: HeaderRecord
-  ): TypedResponse<T> => {
+  ): TypedResponse<T extends JSONValue ? (JSONValue extends T ? never : PrettyJSON<T>) : never> => {
     return {
       response: this.json(object, status, headers),
-      data: object,
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      data: object as any,
       format: 'json',
     }
   }
diff --git a/src/utils/types.ts b/src/utils/types.ts
index 20057566..38b8e25f 100644
--- a/src/utils/types.ts
+++ b/src/utils/types.ts
@@ -10,3 +10,21 @@ export type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) ex
 ) => void
   ? I
   : never
+
+export type JSONPrimitive = string | boolean | number | null | undefined
+export type JSONArray = (JSONPrimitive | JSONObject | JSONArray)[]
+export type JSONObject = { [key: string]: JSONPrimitive | JSONArray | JSONObject }
+export type JSONValue = JSONObject | JSONArray | JSONPrimitive
+
+// `boolean` will be `true` or `false` because it's an alias of them.
+// See: https://github.com/microsoft/TypeScript/issues/22596
+// This type converts `true | false` to `boolean` that we expect.
+type TrueAndFalseToBoolean<T> = T extends true ? boolean : T extends false ? boolean : T
+
+export type PrettyJSON<T> = T extends JSONPrimitive
+  ? TrueAndFalseToBoolean<T>
+  : T extends JSONArray
+  ? PrettyJSON<T[number]>
+  : T extends JSONObject
+  ? { [K in keyof T]: PrettyJSON<T[K]> }
+  : never