Zod 4 support: fix empty function args (#855)

Co-authored-by: Ian Macartney <ian@convex.dev>

Author: Nicolapps

convex/_generated/api.d.ts

@@ -19,6 +19,7 @@ import type * as sessionsExample from "../sessionsExample.js";
 import type * as streamsExample from "../streamsExample.js";
 import type * as testingFunctions from "../testingFunctions.js";
 import type * as triggersExample from "../triggersExample.js";
+import type * as zodFunctionsExample from "../zodFunctionsExample.js";
 
 import type {
   ApiFromModules,
@@ -38,6 +39,7 @@ declare const fullApi: ApiFromModules<{
   streamsExample: typeof streamsExample;
   testingFunctions: typeof testingFunctions;
   triggersExample: typeof triggersExample;
+  zodFunctionsExample: typeof zodFunctionsExample;
 }>;
 
 /**

convex/zodFunctionsExample.ts

@@ -0,0 +1,36 @@
+import { zCustomQuery } from "convex-helpers/server/zod4";
+import { query } from "./_generated/server";
+import { NoOp } from "convex-helpers/server/customFunctions";
+import { z } from "zod/v4";
+
+export const zQuery = zCustomQuery(query, NoOp);
+
+export const noArgs = zQuery({
+  args: {},
+  handler: async (_ctx) => {
+    return "Hello world!";
+  },
+});
+
+const stringToDate = z.codec(z.iso.datetime(), z.date(), {
+  decode: (isoString) => new Date(isoString),
+  encode: (date) => date.toISOString(),
+});
+const dateToString = z.codec(z.date(), z.iso.datetime(), {
+  decode: (date) => date.toISOString(),
+  encode: (isoString) => new Date(isoString),
+});
+
+export const withArgs = zQuery({
+  args: {
+    date: stringToDate,
+  },
+  returns: {
+    oneDayAfter: dateToString,
+  },
+  handler: async (_ctx, args) => {
+    return {
+      oneDayAfter: new Date(args.date.getTime() + 24 * 60 * 60 * 1000),
+    };
+  },
+});

packages/convex-helpers/server/zod4.functions.test.ts

@@ -68,6 +68,13 @@ export const testQuery = zQuery({
   }),
 });
 
+export const testQueryNoArgs = zQuery({
+  args: {},
+  handler: async (_ctx, args) => {
+    assertType<Record<string, never>>(args);
+  },
+});
+
 /**
  * Test zCustomMutation with Zod schemas for args and return value
  */
@@ -254,6 +261,7 @@ export const generateUserId = mutation({
 const testApi: ApiFromModules<{
   fns: {
     testQuery: typeof testQuery;
+    testQueryNoArgs: typeof testQueryNoArgs;
     testMutation: typeof testMutation;
     testAction: typeof testAction;
     returnsNothing: typeof returnsNothing;
@@ -287,6 +295,22 @@ describe("zCustomQuery, zCustomMutation, zCustomAction", () => {
       >();
     });
 
+    describe("zCustomQuery with no args", () => {
+      test("through t.query", async () => {
+        const t = convexTest(schema, modules);
+        const response = await t.query(testApi.testQueryNoArgs);
+        expect(response).toBeNull();
+      });
+
+      test("through t.run", async () => {
+        const t = convexTest(schema, modules);
+        const response = await t.run((ctx) =>
+          ctx.runQuery(testApi.testQueryNoArgs),
+        );
+        expect(response).toBeNull();
+      });
+    });
+
     test("zCustomMutation", async () => {
       const t = convexTest(schema, modules);
       const response = await t.mutation(testApi.testMutation, {

packages/convex-helpers/server/zod4.ts

@@ -960,16 +960,19 @@ type ReturnValueOutput<
 > = [ReturnsValidator] extends [zCore.$ZodType]
   ? Returns<zCore.output<ReturnsValidator>>
   : [ReturnsValidator] extends [ZodFields]
-    ? Returns<zCore.output<zCore.$ZodObject<ReturnsValidator>>>
+    ? Returns<zCore.output<zCore.$ZodObject<ReturnsValidator, zCore.$strict>>>
     : any;
 
 // The args before they've been validated: passed from the client
 type ArgsInput<ArgsValidator extends ZodFields | zCore.$ZodObject<any> | void> =
   [ArgsValidator] extends [zCore.$ZodObject<any>]
     ? [zCore.input<ArgsValidator>]
-    : [ArgsValidator] extends [ZodFields]
-      ? [zCore.input<zCore.$ZodObject<ArgsValidator>>]
-      : OneArgArray;
+    : ArgsValidator extends Record<string, never>
+      ? // eslint-disable-next-line @typescript-eslint/no-empty-object-type
+        [{}]
+      : [ArgsValidator] extends [Record<string, z.ZodTypeAny>]
+        ? [zCore.input<zCore.$ZodObject<ArgsValidator, zCore.$strict>>]
+        : OneArgArray;
 
 // The args after they've been validated: passed to the handler
 type ArgsOutput<

src/App.tsx

@@ -3,6 +3,7 @@ import RelationshipExample from "./components/RelationshipExample";
 import SessionsExample from "./components/SessionsExample";
 import { HonoExample } from "./components/HonoExample";
 import { StreamsExample } from "./components/StreamsExample";
+import { ZodFunctionsExample } from "./components/ZodFunctionsExample";
 import { SessionProvider } from "convex-helpers/react/sessions";
 import { CacheExample } from "./components/CacheExample";
 import { ConvexQueryCacheProvider } from "convex-helpers/react/cache";
@@ -23,6 +24,7 @@ export default function App() {
           <HonoExample />
           <CacheExample />
           <StreamsExample />
+          <ZodFunctionsExample />
         </ConvexQueryCacheProvider>
       </SessionProvider>
     </main>

src/components/ZodFunctionsExample.tsx

@@ -0,0 +1,42 @@
+import { api } from "../../convex/_generated/api";
+import { useQuery } from "convex/react";
+import { useMemo } from "react";
+import { z } from "zod/v4";
+
+const stringToDate = z.codec(z.iso.datetime(), z.date(), {
+  decode: (isoString) => new Date(isoString),
+  encode: (date) => date.toISOString(),
+});
+
+export function ZodFunctionsExample() {
+  const now = useMemo(() => new Date(), []);
+
+  const noArgsResult = useQuery(api.zodFunctionsExample.noArgs);
+  const noArgsResultEmptyArgs = useQuery(api.zodFunctionsExample.noArgs, {});
+  const withArgsResult = useQuery(api.zodFunctionsExample.withArgs, {
+    date: stringToDate.encode(now),
+  });
+
+  return (
+    <div>
+      <h2>Zod Functions Example</h2>
+      <section>
+        <h3>No Args Query</h3>
+        <p>Result: {noArgsResult ?? "Loading..."}</p>
+      </section>
+      <section>
+        <h3>No Args Query (Empty Args)</h3>
+        <p>Result: {noArgsResultEmptyArgs ?? "Loading..."}</p>
+      </section>
+      <section>
+        <h3>With Args Query</h3>
+        {withArgsResult && (
+          <p>
+            One day after:{" "}
+            {stringToDate.decode(withArgsResult.oneDayAfter).toLocaleString()}
+          </p>
+        )}
+      </section>
+    </div>
+  );
+}