feat: add ability to have optionals when chaining input parsers

packages/server/src/core/internals/procedureBuilder.ts

@@ -1,11 +1,6 @@
 import { TRPCError } from '../../error/TRPCError';
 import { getTRPCErrorFromUnknown } from '../../error/utils';
-import {
-  InferOptional,
-  MaybePromise,
-  Simplify,
-  UndefinedKeys,
-} from '../../types';
+import { MaybePromise, Simplify } from '../../types';
 import {
   MiddlewareBuilder,
   MiddlewareFunction,
@@ -68,19 +63,9 @@ export interface BuildProcedure<
       : TParams
   > {}
 
-type Merge<TType, TWith> = {
-  [TKey in keyof TType | keyof TWith]: TKey extends keyof TType
-    ? TKey extends keyof TWith
-      ? TType[TKey] & TWith[TKey]
-      : TType[TKey]
-    : TWith[TKey & keyof TWith];
-};
-
 type OverwriteIfDefined<TType, TWith> = UnsetMarker extends TType
   ? TWith
-  : Simplify<
-      InferOptional<Merge<TType, TWith>, UndefinedKeys<Merge<TType, TWith>>>
-    >;
+  : Simplify<TType & TWith>;
 
 type ErrorMessage<TMessage extends string> = TMessage;
 
@@ -104,9 +89,13 @@ export interface ProcedureBuilder<TParams extends ProcedureParams> {
   input<$Parser extends Parser>(
     schema: TParams['_input_out'] extends UnsetMarker
       ? $Parser
-      : inferParser<$Parser>['out'] extends Record<string, unknown>
-      ? TParams['_input_out'] extends Record<string, unknown>
-        ? $Parser
+      : inferParser<$Parser>['out'] extends Record<string, unknown> | undefined
+      ? TParams['_input_out'] extends Record<string, unknown> | undefined
+        ? undefined extends inferParser<$Parser>['out'] // if current is optional the previous must be too
+          ? undefined extends TParams['_input_out']
+            ? $Parser
+            : ErrorMessage<'Cannot chain an optional parser to a required parser'>
+          : $Parser
         : ErrorMessage<'All input parsers did not resolve to an object'>
       : ErrorMessage<'All input parsers did not resolve to an object'>,
   ): ProcedureBuilder<{

packages/tests/server/input.test.ts

@@ -154,6 +154,146 @@ test('only allow double input validator for object-like inputs', () => {
   }
 });
 
+describe('multiple input validators with optionals', () => {
+  const t = initTRPC.create();
+
+  const webhookProc = t.procedure.input(
+    z
+      .object({
+        id: z.string(),
+        eventTypeId: z.number().optional(),
+      })
+      .optional(),
+  );
+
+  test('2nd parser also optional => merged optional', async () => {
+    const webhookRouter = t.router({
+      byId: webhookProc
+        .input(
+          z
+            .object({
+              webhookId: z.string(),
+            })
+            .optional(),
+        )
+        .query(({ input }) => {
+          expectTypeOf(input).toEqualTypeOf<
+            | {
+                id: string;
+                eventTypeId?: number;
+                webhookId: string;
+              }
+            | undefined
+          >();
+          return input;
+        }),
+    });
+
+    const opts = routerToServerAndClientNew(webhookRouter);
+
+    await expect(opts.proxy.byId.query()).resolves.toBeUndefined();
+    await expect(opts.proxy.byId.query(undefined)).resolves.toBeUndefined();
+    await expect(
+      opts.proxy.byId.query({ id: '123', webhookId: '456' }),
+    ).resolves.toMatchObject({
+      id: '123',
+      webhookId: '456',
+    });
+
+    await opts.close();
+  });
+
+  test('2nd parser required => merged required', async () => {
+    const webhookRouter = t.router({
+      byId: webhookProc
+        .input(
+          z.object({
+            webhookId: z.string(),
+          }),
+        )
+        .query(({ input }) => {
+          expectTypeOf(input).toEqualTypeOf<{
+            id: string;
+            eventTypeId?: number;
+            webhookId: string;
+          }>();
+          return input;
+        }),
+    });
+
+    const opts = routerToServerAndClientNew(webhookRouter);
+
+    await expect(
+      opts.proxy.byId.query({ id: '123', webhookId: '456' }),
+    ).resolves.toMatchObject({
+      id: '123',
+      webhookId: '456',
+    });
+    // @ts-expect-error - missing id and webhookId
+    await expect(opts.proxy.byId.query()).rejects.toThrow();
+    // @ts-expect-error - missing id and webhookId
+    await expect(opts.proxy.byId.query(undefined)).rejects.toThrow();
+    await expect(
+      opts.proxy.byId.query({ id: '123', eventTypeId: 1, webhookId: '456' }),
+    ).resolves.toMatchObject({
+      id: '123',
+      eventTypeId: 1,
+      webhookId: '456',
+    });
+
+    await opts.close();
+  });
+
+  test('with optional keys', async () => {
+    const webhookRouter = t.router({
+      byId: webhookProc
+        .input(
+          z.object({
+            webhookId: z.string(),
+            foo: z.string().optional(),
+          }),
+        )
+        .query(({ input }) => {
+          expectTypeOf(input).toEqualTypeOf<{
+            id: string;
+            eventTypeId?: number;
+            webhookId: string;
+            foo?: string;
+          }>();
+          return input;
+        }),
+    });
+
+    const opts = routerToServerAndClientNew(webhookRouter);
+    await expect(
+      opts.proxy.byId.query({ id: '123', webhookId: '456' }),
+    ).resolves.toMatchObject({
+      id: '123',
+      webhookId: '456',
+    });
+    await expect(
+      opts.proxy.byId.query({ id: '123', webhookId: '456', foo: 'bar' }),
+    ).resolves.toMatchObject({
+      id: '123',
+      webhookId: '456',
+      foo: 'bar',
+    });
+
+    await opts.close();
+  });
+
+  test('cannot chain optional to required', async () => {
+    try {
+      t.procedure
+        .input(z.object({ foo: z.string() }))
+        // @ts-expect-error cannot chain optional to required
+        .input(z.object({ bar: z.number() }).optional());
+    } catch {
+      // whatever
+    }
+  });
+});
+
 test('no input', async () => {
   const t = initTRPC.create();
 
@@ -358,6 +498,12 @@ test('double validators with undefined', async () => {
         return input;
       });
 
+    type Input = inferProcedureParams<typeof proc>['_input_in'];
+    expectTypeOf<Input>().toEqualTypeOf<{
+      roomId: string;
+      optionalKey?: string;
+    }>();
+
     const router = t.router({
       proc,
     });
@@ -388,6 +534,12 @@ test('double validators with undefined', async () => {
         return input;
       });
 
+    type Input = inferProcedureParams<typeof proc>['_input_in'];
+    expectTypeOf<Input>().toEqualTypeOf<{
+      roomId?: string;
+      key: string;
+    }>();
+
     const router = t.router({
       proc,
     });
@@ -421,6 +573,10 @@ test('merges optional with required property', async () => {
       .query(() => 'hi'),
   });
 
+  type Input = inferProcedureInput<typeof router['proc']>;
+  //    ^?
+  expectTypeOf<Input>().toEqualTypeOf<{ id: string }>();
+
   const client = createTRPCProxyClient<typeof router>({
     links: [],
   });