How to Resolve Circular Dependency Issues When Importing Zod Schemas and Validators in TypeScript

Managing schema validations with Zod in TypeScript can become challenging when your schemas and validators reference each other, leading to circular dependency problems. This article explores common issues, explains why they occur, and offers best practices for resolving them effectively.

Understanding the Problem

Suppose you have a Zod schema and custom validators that depend on each other:

“`typescript
// theSchema.ts
import { z } from ‘zod’;
import { validator1 } from ‘./validator1’;
import { validator2 } from ‘./validator2’;

const theSchema = z
.object({
foo: z.literal(‘bar’),
})
.refine(validator1, { error: ‘ERR 1’ })
.refine(validator2, { error: ‘ERR 2’ });

export { theSchema };
“`

“`typescript
// validator1.ts
import { z } from ‘zod’;
import { theSchema } from ‘./theSchema’;

function validator1(data: z.infer) {
return true; // validation logic
}

export { validator1 };
“`

This setup leads to circular import errors, such as:

• Implicit ‘any’ type due to self-referential initialization
• Circular definitions involving theSchema and validator1

Common Errors Encountered

TypeScript may report errors like:

• Implicit ‘any’ type for theSchema because of self-reference
• Circular import of theSchema
• Type inference issues, e.g., data referencing theSchema before its complete definition

Why Do These Errors Occur?

In TypeScript, referencing a module or variable that depends on itself creates a circular dependency. When theSchema uses validators that depend on the schema itself, or vice versa, the compiler cannot resolve the types cleanly, leading to inference errors and import cycles.

Strategies to Fix Circular Dependency

1. Separate Schema Definitions from Validation Logic

Define your schema and validators in separate modules without mutual dependencies, then combine or reference them externally.

“`typescript
// schema.ts
import { z } from ‘zod’;

export const theSchema = z.object({ foo: z.literal(‘bar’) });
“`

“`typescript
// validators.ts
import { z } from ‘zod’;
import { theSchema } from ‘./