MTLProtectedAreaManager

actor MTLProtectedAreaManager

Overview

Protected areas allow user code to be preserved when templates are regenerated, enabling a generate-modify-regenerate workflow where custom code survives regeneration cycles.

Overview

Protected areas work by:

1. Marking sections: Templates define protected areas with unique IDs

2. Scanning existing files: Before regeneration, existing files are scanned

3. Extracting content: Content between protection markers is extracted

4. Preserving during regeneration: Extracted content replaces default content

5. Maintaining markers: Protection markers are preserved in output

Protection Markers

Protected areas are delimited by start/end markers:

// START PROTECTED REGION user-imports
import MyCustomLibrary
// END PROTECTED REGION user-imports

The markers can have custom prefixes (e.g., //, <!--, #) to match the comment syntax of the target language.

Example Usage

let manager = MTLProtectedAreaManager()

// Scan existing file before regeneration
try await manager.scanFile("/output/Person.swift")

// During regeneration, retrieve preserved content
if let content = await manager.getContent("user-imports") {
    // Use preserved content instead of default
}

// After regeneration, check what was preserved
let preserved = await manager.getAllContent()
print("Preserved \(preserved.count) protected areas")