feat: add errorformatter (#1273)

* add errorformatter

* add docs

* changeset

* Update www/src/pages/en/usage/trpc.md

Co-authored-by: Christopher Ehrlich <[email protected]>

---------

Co-authored-by: Christopher Ehrlich <[email protected]>
Co-authored-by: Shoubhit Dash <[email protected]>

.changeset/eighty-masks-invite.md

@@ -0,0 +1,5 @@
+---
+"create-t3-app": minor
+---
+
+feat: add errorformatter for zod errors

cli/package.json

@@ -71,6 +71,7 @@
     "superjson": "^1.12.2",
     "tsup": "^6.6.3",
     "type-fest": "^3.6.0",
-    "typescript": "^4.9.5"
+    "typescript": "^4.9.5",
+    "zod": "^3.21.4"
   }
 }

cli/template/extras/src/server/api/trpc/base.ts

@@ -46,15 +46,25 @@ export const createTRPCContext = (_opts: CreateNextContextOptions) => {
 /**
  * 2. INITIALIZATION
  *
- * This is where the tRPC API is initialized, connecting the context and transformer.
+ * This is where the tRPC API is initialized, connecting the context and transformer. We also parse
+ * ZodErrors so that you get typesafety on the frontend if your procedure fails due to validation
+ * errors on the backend.
  */
 import { initTRPC } from "@trpc/server";
 import superjson from "superjson";
+import { ZodError } from "zod";
 
 const t = initTRPC.context<typeof createTRPCContext>().create({
   transformer: superjson,
-  errorFormatter({ shape }) {
-    return shape;
+  errorFormatter({ shape, error }) {
+    return {
+      ...shape,
+      data: {
+        ...shape.data,
+        zodError:
+          error.cause instanceof ZodError ? error.cause.flatten() : null,
+      },
+    };
   },
 });
 

cli/template/extras/src/server/api/trpc/with-auth-prisma.ts

@@ -61,15 +61,25 @@ export const createTRPCContext = async (opts: CreateNextContextOptions) => {
 /**
  * 2. INITIALIZATION
  *
- * This is where the tRPC API is initialized, connecting the context and transformer.
+ * This is where the tRPC API is initialized, connecting the context and transformer. We also parse
+ * ZodErrors so that you get typesafety on the frontend if your procedure fails due to validation
+ * errors on the backend.
  */
 import { initTRPC, TRPCError } from "@trpc/server";
 import superjson from "superjson";
+import { ZodError } from "zod";
 
 const t = initTRPC.context<typeof createTRPCContext>().create({
   transformer: superjson,
-  errorFormatter({ shape }) {
-    return shape;
+  errorFormatter({ shape, error }) {
+    return {
+      ...shape,
+      data: {
+        ...shape.data,
+        zodError:
+          error.cause instanceof ZodError ? error.cause.flatten() : null,
+      },
+    };
   },
 });
 

cli/template/extras/src/server/api/trpc/with-auth.ts

@@ -59,15 +59,25 @@ export const createTRPCContext = async (opts: CreateNextContextOptions) => {
 /**
  * 2. INITIALIZATION
  *
- * This is where the tRPC API is initialized, connecting the context and transformer.
+ * This is where the tRPC API is initialized, connecting the context and transformer. We also parse
+ * ZodErrors so that you get typesafety on the frontend if your procedure fails due to validation
+ * errors on the backend.
  */
 import { initTRPC, TRPCError } from "@trpc/server";
 import superjson from "superjson";
+import { ZodError } from "zod";
 
 const t = initTRPC.context<typeof createTRPCContext>().create({
   transformer: superjson,
-  errorFormatter({ shape }) {
-    return shape;
+  errorFormatter({ shape, error }) {
+    return {
+      ...shape,
+      data: {
+        ...shape.data,
+        zodError:
+          error.cause instanceof ZodError ? error.cause.flatten() : null,
+      },
+    };
   },
 });
 

cli/template/extras/src/server/api/trpc/with-prisma.ts

@@ -49,15 +49,25 @@ export const createTRPCContext = (_opts: CreateNextContextOptions) => {
 /**
  * 2. INITIALIZATION
  *
- * This is where the tRPC API is initialized, connecting the context and transformer.
+ * This is where the tRPC API is initialized, connecting the context and transformer. We also parse
+ * ZodErrors so that you get typesafety on the frontend if your procedure fails due to validation
+ * errors on the backend.
  */
 import { initTRPC } from "@trpc/server";
 import superjson from "superjson";
+import { ZodError } from "zod";
 
 const t = initTRPC.context<typeof createTRPCContext>().create({
   transformer: superjson,
-  errorFormatter({ shape }) {
-    return shape;
+  errorFormatter({ shape, error }) {
+    return {
+      ...shape,
+      data: {
+        ...shape.data,
+        zodError:
+          error.cause instanceof ZodError ? error.cause.flatten() : null,
+      },
+    };
   },
 });
 

www/src/pages/en/usage/trpc.md

@@ -93,6 +93,36 @@ const UserPage = () => {
 
 You'll immediately notice how good the autocompletion and typesafety is. As soon as you write `api.`, your routers will show up in autocomplete, and when you select a router, its procedures will show up as well. You'll also get a TypeScript error if your input doesn't match the validator that you defined on the backend.
 
+## Inferring errors
+
+By default, `create-t3-app` sets up an [error formatter](https://trpc.io/docs/error-formatting) that lets you infer your Zod Errors if you get validation errors on the backend.
+
+Example usage:
+
+```tsx
+function MyComponent() {
+  const { mutate, error } = api.post.create.useMutation();
+
+  return (
+    <form onSubmit={(e) => {
+      e.preventDefault();
+      const formData = new FormData(e.currentTarget);
+      mutate({ title: formData.get('title') });
+    }}>
+      <input name="title" />
+      {error?.data?.zodError?.fieldErrors.title && (
+        {/** `mutate` returned with an error on the `title` */}
+        <span className="mb-8 text-red-500">
+          {error.data.zodError.fieldErrors.title}
+        </span>
+      )}
+
+      ...
+    </form>
+  );
+}
+```
+
 ## Files
 
 tRPC requires quite a lot of boilerplate that `create-t3-app` sets up for you. Let's go over the files that are generated: