Schema Validation (Lint)

Beyond the attribute-level data_contract_checks, Data Contract Checker can validate each contract against its full JSON Schema. This is the equivalent of a datacontract lint step: it confirms the contract is structurally valid against the specification, catching things like unknown fields, wrong types, and missing required keys.

This works for both:

• Standard contracts — validated against the built-in DCS / ODCS schema for the contract's specification and version.
• Custom contracts — validated against the custom JSON Schema you supply.

Opt-in: off by default

Schema validation is disabled by default. Enable it with the --lint flag or the lint key in your checks config. This keeps the default run focused on your configured checks; turn linting on when you also want full structural validation.

CLI flagConfig file

contract-checker --lint

Use --no-lint to force it off regardless of the config file.

In data-contract-checks.yml:

lint: true

The CLI flag always wins over the config value. The config value must be a YAML boolean; a quoted "false" (or any other non-boolean) is rejected with an error instead of being guessed at.

A custom schema alone does not enable linting

Providing custom_schema_path (or --custom-schema-path) does not turn on validation by itself — lint must be enabled. When linting is off, the custom schema is ignored. If lint was left unset, a warning is shown; an explicit --no-lint or lint: false skips it silently.

What gets validated

lint	custom_schema_path set?	Validated against
off	either	nothing (schema validation skipped)
on	no	built-in schema for the contract's spec/version
on	yes	the custom schema

Schema validation runs in addition to data_contract_checks — both run, and every failure from either is reported. Set data_contract_checks: [] (or omit it) for schema-only validation.

Example

Lint every DCS contract in a directory against the built-in DCS schema:

# data-contract-checks.yml
data_contract_specification: dcs
lint: true
data_contracts_path:
  path: ./contracts/
data_contract_checks: []

contract-checker

A contract with, for example, an unsupported field type is reported as a failure:

✗ FAIL   JSON_SCHEMA   models.orders.fields.attributes   Schema validation failed:
         'array<struct<...>>' is not one of ['number', 'decimal', ... 'struct', ...]

For custom schemas — including extending an existing standard with in-house rules — see Custom Schemas.