zod/src/v4/classic/tests/transform.test.ts

TypeScript-first schema declaration and validation library with static type inference

import { expect, expectTypeOf, test } from "vitest";
import * as z from "zod/v4";

test("transform ctx.addIssue with parse", () => {
  const strs = ["foo", "bar"];
  const schema = z.string().transform((data, ctx) => {
    const i = strs.indexOf(data);
    if (i === -1) {
      ctx.addIssue({
        input: data,
        code: "custom",
        message: `${data} is not one of our allowed strings`,
      });
    }
    return data.length;
  });
  const result = schema.safeParse("asdf");
  expect(result.success).toEqual(false);
  expect(result.error!).toMatchInlineSnapshot(`
    [ZodError: [
      {
        "code": "custom",
        "message": "asdf is not one of our allowed strings",
        "path": []
      }
    ]]
  `);
});

test("transform ctx.addIssue with parseAsync", async () => {
  const strs = ["foo", "bar"];

  const result = await z
    .string()
    .transform(async (data, ctx) => {
      const i = strs.indexOf(data);
      if (i === -1) {
        ctx.addIssue({
          input: data,
          code: "custom",
          message: `${data} is not one of our allowed strings`,
        });
      }
      return data.length;
    })
    .safeParseAsync("asdf");

  expect(result).toMatchInlineSnapshot(`
    {
      "error": [ZodError: [
      {
        "code": "custom",
        "message": "asdf is not one of our allowed strings",
        "path": []
      }
    ]],
      "success": false,
    }
  `);
});

test("z.NEVER in transform", () => {
  const foo = z
    .number()
    .optional()
    .transform((val, ctx) => {
      if (!val) {
        ctx.addIssue({
          input: val,
          code: z.ZodIssueCode.custom,
          message: "bad",
        });
        return z.NEVER;
      }
      return val;
    });
  type foo = z.infer<typeof foo>;
  expectTypeOf<foo>().toEqualTypeOf<number>();
  const arg = foo.safeParse(undefined);
  if (!arg.success) {
    expect(arg.error.issues[0].message).toEqual("bad");
  }
});

test("basic transformations", () => {
  const r1 = z
    .string()
    .transform((data) => data.length)
    .parse("asdf");
  expect(r1).toEqual(4);
});

test("coercion", () => {
  const numToString = z.number().transform((n) => String(n));
  const data = z
    .object({
      id: numToString,
    })
    .parse({ id: 5 });

  expect(data).toEqual({ id: "5" });
});

test("async coercion", async () => {
  const numToString = z.number().transform(async (n) => String(n));
  const data = await z
    .object({
      id: numToString,
    })
    .parseAsync({ id: 5 });

  expect(data).toEqual({ id: "5" });
});

test("sync coercion async error", async () => {
  const asyncNumberToString = z.number().transform(async (n) => String(n));
  expect(() =>
    z
      .object({
        id: asyncNumberToString,
      })
      .parse({ id: 5 })
  ).toThrow();
  // expect(data).toEqual({ id: '5' });
});

test("default", () => {
  const data = z.string().default("asdf").parse(undefined); // => "asdf"
  expect(data).toEqual("asdf");
});

test("dynamic default", () => {
  const data = z
    .string()
    .default(() => "string")
    .parse(undefined); // => "asdf"
  expect(data).toEqual("string");
});

test("default when property is null or undefined", () => {
  const data = z
    .object({
      foo: z.boolean().nullable().default(true),
      bar: z.boolean().default(true),
    })
    .parse({ foo: null });

  expect(data).toEqual({ foo: null, bar: true });
});

test("default with falsy values", () => {
  const schema = z.object({
    emptyStr: z.string().default("def"),
    zero: z.number().default(5),
    falseBoolean: z.boolean().default(true),
  });
  const input = { emptyStr: "", zero: 0, falseBoolean: true };
  const output = schema.parse(input);
  // defaults are not supposed to be used
  expect(output).toEqual(input);
});

test("object typing", () => {
  const stringToNumber = z.string().transform((arg) => Number.parseFloat(arg));

  const t1 = z.object({
    stringToNumber,
  });

  type t1 = z.input<typeof t1>;
  type t2 = z.output<typeof t1>;

  expectTypeOf<t1>().toEqualTypeOf<{ stringToNumber: string }>();
  expectTypeOf<t2>().toEqualTypeOf<{ stringToNumber: number }>();
});

test("transform method overloads", () => {
  const t1 = z.string().transform((val) => val.toUpperCase());
  expect(t1.parse("asdf")).toEqual("ASDF");

  const t2 = z.string().transform((val) => val.length);
  expect(t2.parse("asdf")).toEqual(4);
});

test("multiple transformers", () => {
  const stringToNumber = z.string().transform((arg) => Number.parseFloat(arg));

  const doubler = stringToNumber.transform((val) => {
    return val * 2;
  });
  expect(doubler.parse("5")).toEqual(10);
});

test("short circuit on dirty", () => {
  const schema = z
    .string()
    .refine(() => false)
    .transform((val) => val.toUpperCase());
  const result = schema.safeParse("asdf");
  expect(result.success).toEqual(false);

  expect(result.error).toMatchInlineSnapshot(`
    [ZodError: [
      {
        "code": "custom",
        "path": [],
        "message": "Invalid input"
      }
    ]]
  `);

  const result2 = schema.safeParse(1234);
  expect(result2.success).toEqual(false);
  if (!result2.success) {
    expect(result2.error.issues[0].code).toEqual(z.ZodIssueCode.invalid_type);
  }
});

test("async short circuit on dirty", async () => {
  const schema = z
    .string()
    .refine(() => false)
    .transform((val) => val.toUpperCase());
  const result = await schema.spa("asdf");
  expect(result.success).toEqual(false);

  expect(result.error).toMatchInlineSnapshot(`
    [ZodError: [
      {
        "code": "custom",
        "path": [],
        "message": "Invalid input"
      }
    ]]
  `);

  const result2 = await schema.spa(1234);
  expect(result2.success).toEqual(false);

  expect(result2.error).toMatchInlineSnapshot(`
    [ZodError: [
      {
        "expected": "string",
        "code": "invalid_type",
        "path": [],
        "message": "Invalid input: expected string, received number"
      }
    ]]
  `);
});