hard Data Validation

JSON Schema Validator

The Brief

A SaaS platform takes JSON payloads from third-party integrators. Bad data has been silently corrupting their database for months. They want a schema validator built from scratch — no third-party libraries — that compares an incoming dict against a schema definition and returns every violation, not just the first one.

Support these schema types: string, integer, number, boolean, array, object. Plus constraints: required fields, min/max for numbers, minLength/maxLength for strings, minItems/maxItems for arrays, enum (whitelist of allowed values), and nested object/array schemas.

Acceptance Criteria

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1 Array

2 Array

3 Array

4 Array

💡 Hints 0 / 5

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solution.py

Python 3

def validate(data, schema, path="$"):
    """Return list of error messages. Empty list = valid."""
    errors = []
    # TODO: dispatch on schema["type"]
    # TODO: support required, min/max, minLength/maxLength, minItems/maxItems, enum
    # TODO: recurse into object properties and array items
    return errors


if __name__ == "__main__":
    schema = {
        "type": "object",
        "required": ["name", "age", "tags"],
        "properties": {
            "name": {"type": "string", "minLength": 1, "maxLength": 50},
            "age":  {"type": "integer", "min": 0, "max": 150},
            "tags": {"type": "array", "minItems": 1, "items": {"type": "string"}},
        },
    }
    print(validate({"name": "", "age": 200, "tags": []}, schema))

Console