Errors and Validation

Validation is what stops ToonUI from becoming “just parse whatever string came back.”

Validation issue codes

Current issue codes:

• INVALID_COMPONENT
• INVALID_PROP
• INVALID_VARIANT
• MISSING_REQUIRED_FIELD
• INVALID_NESTING
• INVALID_SYNTAX
• UNSAFE_CONTENT

What validation checks

• required fields exist
• variants belong to the official catalog
• nesting rules are respected
• forms include fields and a submit button
• list-like structures contain valid child node types
• tables keep column and row counts aligned
• unsafe raw HTML/script-like content is rejected in text nodes

Examples

Missing required field

form "Create product":
  button primary "Create" submit

This is invalid because a form must include at least one field.

Invalid nesting

list "Products":
  text "This is not allowed directly inside list"

This is invalid because lists can only contain item nodes.

Unsafe content

text "<script>alert('xss')</script>"

This is invalid because raw script-like HTML is not allowed in text nodes.

Practical recommendation

Treat parsing and validation as part of the contract, not as optional polish.

If the host app cares about reliability, it MUST validate generated structure before trusting it.

Next step

1. Debug Invalid ToonUI
2. Complete Syntax Reference