# Deprecation Detection Implementation Summary
## What Was Built
A generic, extensible deprecation detection and warning system for the Ember docs MCP server that automatically surfaces deprecation warnings across all tool responses.
## Files Created/Modified
### New Files
1. **`lib/deprecation-manager.js`** (250+ lines)
- Core deprecation detection logic
- Multiple warning format generators
- Content analysis for automatic deprecation detection
- Registry of known deprecated APIs
2. **`test/deprecation-manager.test.js`** (250+ lines)
- Comprehensive test coverage (24 tests)
- Tests all detection methods and warning formats
- Validates known deprecations and content analysis
3. **`DEPRECATION_DETECTION.md`**
- Complete documentation of the system
- Architecture overview
- Usage examples
- Extension guide
### Modified Files
1. **`lib/documentation-service.js`**
- Integrated DeprecationManager
- Added deprecation analysis during parsing
- Enriched API entries with deprecation info
- Enhanced search results with deprecation flags
2. **`index.js`** (MCP Server)
- Updated `formatSearchResults()` - adds deprecation indicators to titles
- Updated `formatApiReference()` - adds banner warnings
- Updated `formatBestPractices()` - warns for deprecated topics
## How It Works
### Detection Strategy
The system uses multiple approaches to detect deprecations:
1. **Hardcoded Known Deprecations**: ArrayProxy, ObjectProxy, PromiseProxyMixin, Evented
2. **Keyword Detection**: Scans for "deprecated", "legacy", "not recommended", etc.
3. **Pattern Extraction**: Extracts version numbers and modern alternatives
4. **Documentation Analysis**: Parses deprecation guide sections automatically
### Warning Formats
- **Banner**: Full warning with reason and alternatives (API references)
- **Inline**: Compact warning with key info (search results)
- **Short**: Minimal indicator (result titles)
### Integration Points
All three MCP tools now show deprecation warnings:
- `search_ember_docs` - Flags in results with inline warnings
- `get_api_reference` - Banner at top of API docs
- `get_best_practices` - Warning if topic is deprecated
## Example Output
When looking up ArrayProxy:
```markdown
# ArrayProxy
> ⚠️ **DEPRECATION WARNING**
>
> **`ArrayProxy` is deprecated**
>
> Native Proxy is now available in all supported environments
>
> **Modern Alternative:** Use tracked properties and native arrays for reactive data
**Module:** `@ember/array/proxy`
...
```
## Benefits
1. **Automatic**: Detects deprecations from documentation content
2. **Generic**: Works for any deprecated API, not just hardcoded ones
3. **Contextual**: Shows version info, reasons, and modern alternatives
4. **Non-intrusive**: Still returns deprecated APIs, just with warnings
5. **Extensible**: Easy to add new deprecations or detection patterns
6. **Well-tested**: 61 total tests pass (24 specifically for deprecation system)
## Technical Details
- **Architecture**: Clean separation with DeprecationManager class
- **Performance**: Deprecation analysis happens once at documentation load time
- **Maintainability**: Single source of truth for deprecation logic
- **Type Safety**: JSDoc annotations throughout
## Test Results
```
✓ test/deprecation-manager.test.js (24 tests)
✓ test/integration.test.js (13 tests)
✓ test/documentation-service.test.js (24 tests)
Test Files 3 passed (3)
Tests 61 passed (61)
```
## Future Enhancements
The system is designed to be easily extended:
- Version-aware recommendations
- Migration code snippets
- RFC tracking integration
- Severity levels (error/warning/info)
- Timeline tracking (when introduced/removed)