fix(validation-errors): server validation errors were incorrectly processed by typeschema clients

Author: TheEdoRan

packages/next-safe-action/src/action-builder.ts

@@ -14,7 +14,7 @@ import type {
 } from "./index.types";
 import type { InferArray } from "./utils";
 import { ActionMetadataError, DEFAULT_SERVER_ERROR_MESSAGE, isError, zodValidate } from "./utils";
-import { ActionServerValidationError, buildValidationErrors } from "./validation-errors";
+import { buildValidationErrors } from "./validation-errors";
 import type {
 	BindArgsValidationErrors,
 	HandleBindArgsValidationErrorsShapeFn,
@@ -212,7 +212,15 @@ export function actionBuilder<
 							}
 
 							// If error is `ActionServerValidationError`, return `validationErrors` as if schema validation would fail.
-							if (e instanceof ActionServerValidationError) {
+							// Shouldn't be this difficult to check for `ActionServerValidationError`, but /typeschema clients fail
+							// if it's not done this way.
+							if (
+								e instanceof Error &&
+								"kind" in e &&
+								"validationErrors" in e &&
+								typeof e.kind === "string" &&
+								e.kind === "__actionServerValidationError"
+							) {
 								const ve = e.validationErrors as ValidationErrors<S>;
 								middlewareResult.validationErrors = await Promise.resolve(args.handleValidationErrorsShape(ve));
 							} else {

packages/next-safe-action/src/typeschema.ts

@@ -23,8 +23,8 @@ export type * from "./validation-errors.types";
 
 /**
  * Create a new safe action client.
- * This client supports multiple validation libraries via [TypeSchema](https://typeschema.com). If you experience
- * issues when using this, switch to the main client exported from `next-safe-action`, which just supports Zod.
+ * Note: this client only works with Zod as the validation library.
+ * If you want to use a validation library supported by [TypeSchema](https://typeschema.com), import this client from `/typeschema` path.
  * @param createOpts Optional initialization options
  *
  * {@link https://next-safe-action.dev/docs/safe-action-client/initialization-options See docs for more information}
@@ -56,7 +56,7 @@ export const createSafeActionClient = <
 		middlewareFns: [async ({ next }) => next({ ctx: undefined })],
 		handleServerErrorLog,
 		handleReturnedServerError,
-		validationStrategy: "zod",
+		validationStrategy: "typeschema",
 		schema: undefined,
 		bindArgsSchemas: [],
 		ctxType: undefined,

packages/next-safe-action/src/validation-errors.ts

@@ -53,10 +53,12 @@ export const buildValidationErrors = <S extends Schema | undefined>(issues: Vali
 // This class is internally used to throw validation errors in action's server code function, using
 // `returnValidationErrors`.
 export class ActionServerValidationError<S extends Schema> extends Error {
+	public kind: string;
 	public validationErrors: ValidationErrors<S>;
 	constructor(validationErrors: ValidationErrors<S>) {
-		super("Server Validation Error");
+		super("Action server validation error");
 		this.validationErrors = validationErrors;
+		this.kind = "__actionServerValidationError";
 	}
 }