Enhanced Message Validation with Schema Introspection for Publishers, Services, and Actions

[mahmoud-ghalayini]

The Problem

Current message validation in rclnodejs is minimal:

1. Cryptic errors - Publishing invalid messages results in generic "serialization failed" errors with no indication of what field or type is wrong
2. Silent failures - Unknown fields are silently ignored, leading to hard-to-debug issues
3. No schema introspection - No programmatic way to inspect message structure at runtime

Solution

Enhance message validation with:

1. Schema Introspection APIs

• getMessageSchema(typeClass) - Get full schema for any message type
• getFieldNames(typeClass) - List field names
• getFieldType(typeClass, fieldName) - Get type info for specific field

2. Validation Functions

• validateMessage(obj, typeClass, options) - Returns {valid, issues[]}
• assertValidMessage(obj, typeClass, options) - Throws on invalid
• createMessageValidator(typeClass, options) - Reusable validator

3. Structured Error Reporting

• New MessageValidationError class with field-level issue details
• ValidationProblem enum: TYPE_MISMATCH, UNKNOWN_FIELD, MISSING_FIELD, etc.

4. Validation Options

• strict: true - Error on unknown fields
• checkTypes: true - Validate field types
• Nested message validation support