jsonschema Format Validation Configuration

This repository demonstrates how to properly configure the jsonschema crate (version 0.30.0) to correctly validate IPv6 addresses.

Understanding Format Validation in jsonschema

The jsonschema crate requires explicitly enabling format validation via the should_validate_formats(true) method. This is not a bug but rather by design - format validation is optional according to the JSON Schema specification.

Correct Configuration

To properly validate formats like IPv6 addresses, the validator must be configured as follows:

let validator = jsonschema::draft202012::options()
    .should_validate_formats(true)  // This line is required!
    .build(&schema)?;

Without this configuration, format validation checks will not be performed, and invalid IPv6 addresses would pass validation.

Validation Schema

{
  "$schema": "http://json-schema.org/draft-2020-12/schema",
  "type": "object",
  "properties": {
    "address": {
      "type": "string",
      "anyOf": [
        {
          "format": "ipv4"
        },
        {
          "format": "ipv6"
        }
      ]
    }
  },
  "required": [
    "address"
  ]
}

Testing With Proper Configuration

When properly configured with .should_validate_formats(true), the crate correctly:

• Validates proper IPv6 addresses like 2001:0db8:85a3:0000:0000:8a2e:0370:7334
• Rejects invalid addresses like 2001:0db8:85a3:0000:0000:8a2e:0370:7334:5678 (too many segments)

Steps to Demonstrate

1. Clone this repository
2. Run cargo run
3. Observe that invalid IPv6 addresses correctly fail validation

Additional Information

The solution was confirmed by the crate maintainer in GitHub Issue #743.

Technical Details

A valid IPv6 address must:

• Have exactly 8 segments (when fully expanded)
• Each segment must be a valid hexadecimal value between 0 and FFFF
• Can be compressed using the :: notation to represent one or more groups of zeros

Environment Information

• jsonschema: 0.30.0
• Rust: 1.86.0
• OS: Darwin Kernel Version 24.5.0 (x86_64)