# `react-doctor/zod-v4-no-deprecated-error-customization`

Replace deprecated Zod error customization with the v4 unified { error } API: z.string({ error: "Required" })

- **Status:** Active
- **Category:** Architecture
- **Assessment:** Evidence-required risk
- **Required evidence:** source code, repository context
- **Default configuration:** Enabled
- **Default severity:** warn
- **Scope:** All supported frameworks
- **Active when:** always
- **Requirements:** zod:4
- **Tags:** migration-hint
- **Priority:** 34 (P3)
- **Source:** oxlint-plugin-react-doctor
- **Rule set:** oxlint-plugin-react-doctor 0.9.3 (prompt schema 2)
- **Documentation:** [Official documentation](https://zod.dev/error-customization)

## Validation prompt

Confirm the detector match and collect the required evidence before deciding whether an edit is warranted.

Fires on a CallExpression in two shapes. (1) Factory path: the callee resolves through a zod import binding to a factory in ZOD_FACTORIES_WITH_ERROR_PARAMS (z.string, aliased string as zString, zod.number, etc.) AND either the factory is one of bigint/boolean/date/number/string with a string-literal FIRST argument (z.string("Required")), or ANY argument is an object literal containing a property named errorMap, invalid_type_error, or required_error (z.number({ invalid_type_error: "..." }), z.enum(["admin"], { errorMap: () => ... })). (2) Parse path: a .parse/.safeParse/.parseAsync/.safeParseAsync call whose receiver is itself a direct zod factory call, passing a second-arg object with an errorMap property (z.string().safeParseAsync(value, { errorMap })). False positives a reviewer suppresses: already-migrated z.string({ error: "Required" }); string literals that are schema VALUES not messages, e.g. z.literal("draft"), z.enum(["pro","scale"]), z.literal inside a union; first string args on non-message factories like z.record(z.string(), z.unknown()), z.map, z.set; non-zod lookalikes where z is not a zod import (const z = createValidator()); and a parse errorMap on a variable-aliased schema (const schema = z.string(); schema.parse(value, { errorMap })) because the receiver is an identifier, not a direct factory call.

## Evidence boundary

The diagnostic proves only that the detector's modeled source pattern matched. It does not prove runtime impact, product intent, rendered failure, or that one remediation is correct.

Establish the environment, explicit repository policy, relevant exceptions, and required rendered or runtime evidence before deciding the occurrence. This page’s Assessment and Required evidence fields define the review contract.

Default severity is registry metadata. Use the occurrence's JSON severity after repository configuration when ordering real findings.

Record one outcome:

- **Confirmed failure:** The required evidence establishes the violation.
- **Rejected:** A documented exception or false-positive predicate applies.
- **Needs evidence:** Named evidence can still be collected.
- **Unavailable:** Required evidence cannot be collected in this run.
- **Waived with evidence:** An authorized, scoped exception applies to an established failure.
- **Observation:** The review records an optional tradeoff without claiming a defect.

A waiver records its scope, authority, evidence, and review or expiry condition. It is not a pass or false positive.

## Fix prompt

Apply this candidate correction only after the required evidence confirms the risk.

Migrate to Zod 4's unified error customization. Replace a legacy first-arg message string with the error key: z.string("Required") becomes z.string({ error: "Required" }). Replace invalid_type_error/required_error with a single error callback that branches on issue.input: z.string({ error: (issue) => issue.input === undefined ? "Required" : "Must be a string" }). Replace an errorMap option (on a factory or in a parse/safeParse second argument) with the same error key, returning a string or { message }: z.enum(["admin"], { error: () => "Role" }) and schema.parse(value, { error: () => "Bad" }). See https://zod.dev/error-customization

## Repository-wide copy prompt

Use this only for a repository-wide pass after validating each occurrence. For one occurrence, use the occurrence-level guidance above.

````text
Fix every confirmed `react-doctor/zod-v4-no-deprecated-error-customization` diagnostic in the current repository.

Required change:
- Migrate to Zod 4's unified error customization. Replace a legacy first-arg message string with the error key: z.string("Required") becomes z.string({ error: "Required" }). Replace invalid_type_error/required_error with a single error callback that branches on issue.input: z.string({ error: (issue) => issue.input === undefined ? "Required" : "Must be a string" }). Replace an errorMap option (on a factory or in a parse/safeParse second argument) with the same error key, returning a string or { message }: z.enum(["admin"], { error: () => "Role" }) and schema.parse(value, { error: () => "Bad" }). See https://zod.dev/error-customization.

Validation before editing:
Fires on a CallExpression in two shapes. (1) Factory path: the callee resolves through a zod import binding to a factory in ZOD_FACTORIES_WITH_ERROR_PARAMS (z.string, aliased string as zString, zod.number, etc.) AND either the factory is one of bigint/boolean/date/number/string with a string-literal FIRST argument (z.string("Required")), or ANY argument is an object literal containing a property named errorMap, invalid_type_error, or required_error (z.number({ invalid_type_error: "..." }), z.enum(["admin"], { errorMap: () => ... })). (2) Parse path: a .parse/.safeParse/.parseAsync/.safeParseAsync call whose receiver is itself a direct zod factory call, passing a second-arg object with an errorMap property (z.string().safeParseAsync(value, { errorMap })). False positives a reviewer suppresses: already-migrated z.string({ error: "Required" }); string literals that are schema VALUES not messages, e.g. z.literal("draft"), z.enum(["pro","scale"]), z.literal inside a union; first string args on non-message factories like z.record(z.string(), z.unknown()), z.map, z.set; non-zod lookalikes where z is not a zod import (const z = createValidator()); and a parse errorMap on a variable-aliased schema (const schema = z.string(); schema.parse(value, { errorMap })) because the receiver is an identifier, not a direct factory call.

Constraints:
- Make the smallest change that fixes the root cause.
- Preserve behavior and interfaces unrelated to this diagnostic.
- Reuse existing project components, utilities, and conventions.
- Adapt identifiers and framework details instead of copying blindly.
- Do not disable the rule or suppress matching code.

Assessment:
- Record detector evidence, applicability facts, assumptions, missing evidence, and the rule class for this occurrence.
- Return one outcome: Confirmed failure, Rejected, Needs evidence, Unavailable, Waived with evidence, or Observation.
- A waiver records the established failure, scope, authority, evidence, and review or expiry condition. It is not a pass or false positive.

Verification:
- Run focused tests for the changed behavior.
- Run React Doctor and confirm this diagnostic no longer appears from changed code.
- Run an unfiltered scan of the affected scope before claiming no cross-category regression.
- Report the files changed and any checks you could not run.
````