Rich Text Editor Component: Hard Validation Mode for Server-Side Sanitization

[andrewbrazzatti]

Summary

This issue tracks the implementation of a “hard validation mode” for the RichTextEditorComponent, where a validation error is returned if server-side sanitization modifies submitted content.

PR #3689 introduced the TipTap-based RichTextEditorComponent with client-side sanitization safeguards and loop prevention. Currently, if server-side sanitization alters submitted content, the system tolerates the change. In hard validation mode, this behaviour would instead result in a validation error, preventing silent mutation of user input.

This feature is particularly important for institutions with strict content integrity, compliance, or audit requirements.

---

Background

PR: #3689

The PR delivered:

• RichTextEditorComponent integrated into the config-driven form framework
• TipTap and ngx-tiptap integration
• Markdown to HTML conversion and source mode support
• Client-side sanitization safeguards
• Synchronization with Angular form controls
• Full unit test coverage
• Internationalisation support for editor UI elements
• CI updates for new :ci test commands

While sanitization is already performed, there is currently no strict enforcement mechanism when the server modifies content. This can lead to silent differences between what a user submits and what is ultimately stored.

---

Problem Statement

In environments with higher security or governance requirements, silently altering user-submitted rich text content on the server may be unacceptable.

Examples include:

• Removal of disallowed HTML elements or attributes
• Script stripping
• Inline style filtering
• Structural normalization of markup

In such cases, the system should:

• Detect that sanitization has altered the submitted content
• Reject the submission
• Return a validation error indicating that the content must be corrected

This prevents data drift and ensures that stored content always matches user intent without silent mutation.

---

Objectives

• Introduce a configurable hard validation mode for rich text fields
• Detect when server-side sanitization modifies submitted content
• Return a validation error instead of silently accepting sanitized content
• Provide clear and actionable error messaging to end users
• Maintain backward compatibility with existing behaviour by default

---

Proposed Scope

1. Sanitization Comparison Logic

• Capture the original submitted content
• Apply server-side sanitization
• Compare original and sanitized output
• Determine whether a meaningful difference exists

Define what constitutes a failure condition, for example:

• Structural HTML changes
• Attribute removal
• Content removal

Clarify whether whitespace-only differences should be ignored.

2. Configuration Model

• Extend the RichTextEditorComponent schema configuration to support a flag such as:

  • hardSanitizationValidation: true

• Ensure the default behaviour remains non-breaking (soft mode)

3. Validation Behaviour

• When hard mode is enabled:

  • Reject submission if sanitization alters content
  • Return a validation error from the API
  • Surface the error in the Angular form control state

• Ensure error messages are:

  • Clear
  • Internationalised
  • Specific enough to guide correction

4. UI Feedback

• Display validation errors inline within the form
• Optionally provide contextual guidance, such as:
  • “Your content contains disallowed formatting”
  • “Please remove unsupported HTML elements”

5. Testing

• Unit tests for sanitization comparison logic
• Integration tests for form submission behaviour in hard mode
• Regression tests ensuring existing soft behaviour remains unchanged
• Edge case tests for markdown conversion and source mode interactions

---

Acceptance Criteria

• A configuration flag enables hard validation mode
• Submissions that are altered by server-side sanitization are rejected
• Clear validation errors are returned to the client
• Errors are displayed correctly in the Angular form
• Existing behaviour remains unchanged when hard mode is disabled
• Unit and integration tests cover the new behaviour
• CI builds and tests pass

---

Out of Scope

• Redesign of the sanitization library itself
• Introduction of new TipTap extensions
• Performance optimisations unrelated to validation logic

---

Notes

The implementation must ensure that content integrity is enforceable without introducing breaking changes for existing deployments unless explicitly configured.