Schema Validator

Requirements

• Export schema as named and default, plus ValidationError. schema.string(), schema.number(), and schema.boolean() create primitive schemas with parse(input), safeParse(input), and optional().
• Primitive schemas use exact types without coercion. Strings include empty strings; numbers must be finite; booleans accept only true or false. optional() returns a new schema that additionally accepts undefined without changing the original.
• safeParse returns { success: true, data } or { success: false, errors }. Each error has path and message. Primitive paths are []; messages are "Expected string", "Expected finite number", or "Expected boolean".
• parse returns validated data or throws ValidationError with name "ValidationError", message "Validation failed", and an issues array equal in content to safeParse errors.
• schema.object(shape) accepts a flat shape whose values are primitive schemas. Validate plain objects including null-prototype objects, but reject null, arrays, and non-plain objects with a root error "Expected plain object".
• Object validation reads only own properties, reports all invalid fields in shape-key order with paths [fieldName], strips unknown keys, and returns a fresh ordinary object. Omit missing optional fields; preserve explicitly present undefined fields. Missing required fields fail their primitive schema.
• Capture the shape at construction, do not mutate inputs or schemas, and safely define special keys such as __proto__. TypeScript infers required and optional field types. Nested objects, arrays, coercion, refinements, and getter-bearing input are outside scope.

Examples

Input: const user = schema.object({ name: schema.string(), age: schema.number().optional() });
user.safeParse({ name: "Ada", extra: true });
Output: { success: true, data: { name: "Ada" } }

Input: user.safeParse({ name: 3, age: "20" });
Output: Two errors: ["name"] / "Expected string", then ["age"] / "Expected finite number".