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Validate Nested Configuration Objects

Applied IntuitionMachine Learning Engineer · Technical Screen
HardMachine Learning EngineerTechnical ScreenCoding & Algorithms

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This question evaluates schema validation skills including recursive data structures, primitive and composite type checking, and structured error reporting for configuration objects, categorized under Coding & Algorithms for a Machine Learning Engineer role and focused on practical implementation.

You are given a set of custom descriptor objects that define the expected schema of a configuration object. Implement a validator that checks whether an input configuration matches the descriptor.

A descriptor may describe:

  • A primitive value, such as string, number, boolean, or null.
  • An object with named fields, where each field has its own descriptor.
  • A list, where every element must match the list element descriptor.

For this problem, assume all fields defined in an object descriptor are required unless stated otherwise, and fields not present in the descriptor should be reported as unexpected.

Example descriptor:

PersonDescriptor:
 name: string
 email: string
 address: AddressDescriptor

AddressDescriptor:
 street: string
 city: string

Example input:

{
 "name": "John Adams",
 "email": "[email protected]",
 "address": "111 street"
}

The input is invalid because address is expected to be an object matching AddressDescriptor, but the provided value is a string.

Implement:

validate(config, descriptor) -> list of validation errors

The validator should recursively check nested object descriptors and list descriptors. Each validation error should include enough information to identify where the problem occurred, such as the field path and the expected versus actual type.

Your implementation should handle at least the following cases:

  1. Missing required fields.
  2. Unexpected extra fields.
  3. Primitive type mismatches.
  4. Nested object validation.
  5. List validation, including invalid element types.
  6. Clear error reporting for multiple errors in the same config.

Do not use an external schema validation library.