What Is Update Detection?

When a reusable code block (e.g. from a Custom Code entity, Layout, or Template) is injected into a compiled file, JCB wraps that block with special comment markers known as insert/replace tags. On future rebuilds, JCB uses those tags to:

• Compare the original code vs. the code currently in the file
• Identify any differences between versions
• Warn you if a manual edit was made to an injected block
• Decide whether to update, skip, or log the conflict

This mechanism ensures safe “round-trip” workflows — you can edit compiled files (for example, via IDE sync), and JCB will detect if something’s been changed and react accordingly.

How It Works

1. You define and inject a reusable Custom Code block (e.g. validation.php).
2. On compile, JCB adds that block with identifiable comment tags (e.g. // [CODE: my_block]).
3. You edit the compiled file manually (or fetch from IDE).
4. Next compile: JCB reads both the new version and original block.
5. If a mismatch is found, it presents a diff and logs the override.

Key Features

• 🔍 Visual Diff Comparison: Side-by-side detection of modified vs. original blocks, showing additions, deletions, and changes.
• 🔁 Round-Trip Safety: Changes in compiled files are not blindly overwritten — JCB flags them for inspection.
• 📑 Central Diff Logging: Changes are logged to the compiler logs for inspection and tracking.
• 🧠 Smart Context Recognition: Diffing is aware of comment-style, language syntax, and block context (HTML, PHP, etc.).
• 🛑 Warning System: Displays alerts in the compile summary when it finds mismatches or injected code that was edited.
• 💾 Override Preservation: You can choose to preserve manual edits and skip automatic replacement, depending on your development strategy.

Use Cases

• You edited compiled logic in your IDE and want to preserve it during JCB rebuild.
• You’re collaborating and want to see what changed in a shared code block.
• You manage version-controlled blueprints and want to avoid unintended regressions.

Why It Matters

• ✅ Prevents Accidental Overwrites: Manual changes are never lost without warning.
• ✅ Enables Round-Trip Coding: Fetch > Edit > Compile again — all with safety nets.
• ✅ Facilitates Collaboration: See who made what changes when working in teams.

Conclusion

Update detection and visual diffing is one of JCB’s most powerful safety features — enabling intelligent, traceable compilation. You keep full control of your overrides and code changes, and JCB makes sure nothing is lost along the way. Whether you’re working alone or with a team, it gives you peace of mind and protects your logic.

Summary

JCB tracks injected and reused code with a visual diff system, allowing you to detect changes between the original and compiled code — preserving overrides, alerting you to differences, and helping prevent accidental loss of edits during rebuilds.