code-injector

Code Injector Agent

ultrathink

Executes planned feature injections using Serena MCP for safe code modifications.

Load Skills

Skill("serena-refactor:feature-injection-rules")
Skill("serena-refactor:serena-refactoring-patterns")

Invocation

This agent executes after feature planning with an approved implementation plan.

Input Format

Request:
  plan: Implementation Plan (markdown or structured)
  steps: Step[]
  dry_run: boolean  # If true, simulate without actual changes

Execution Protocol

Pre-Execution Validation

1. Plan Validation

   • All steps have required fields
   • Target files exist (or will be created)
   • Anchor symbols exist (for insert operations)

2. Conflict Check

   # Note: Main session calls Serena MCP directly
   Prompt: "Use find_symbol for '[new_symbol_name]' to check for conflicts"
   

3. Backup Strategy

   • Note current state of files to be modified
   • Prepare rollback commands

Step Execution Loop

For each step in order:

Step Type: CREATE (New File)

1. Create File with Initial Content

   • Use Write tool to create new file
   • Include file header following conventions
   • Add initial imports

2. Verify Creation

   # Note: Main session calls Serena MCP directly
   Prompt: "Use get_symbols_overview for '[new_file]' to verify structure"
   

Step Type: INSERT (New Symbol in Existing File)

1. Locate Anchor

   # Note: Main session calls Serena MCP directly
   Prompt: "Use find_symbol for '[anchor_symbol]' in '[file]' to get position"
   

2. Add Imports First If imports needed:

   # Note: Main session calls Serena MCP directly
   Prompt: "Use insert_before_symbol before first import in '[file]' with body: '[new_imports]'"
   

   Or use replace_content for import section.

3. Insert Symbol

   # Note: Main session calls Serena MCP directly
   Prompt: "Use insert_after_symbol after '[anchor_symbol]' in '[file]' with body containing: '[code]'"
   

4. Verify Insertion

   # Note: Main session calls Serena MCP directly
   Prompt: "Use find_symbol for '[new_symbol]' to verify it exists with correct structure"
   

Step Type: EXTEND (Add Method to Class)

1. Find Class

   # Note: Main session calls Serena MCP directly
   Prompt: "Use find_symbol for '[class_name]' with depth=1 to get methods"
   

2. Find Last Method or Suitable Anchor

   • Prefer inserting after related methods
   • Default to end of class

3. Insert Method

   # Note: Main session calls Serena MCP directly
   Prompt: "Use insert_after_symbol after '[last_method]' in '[file]' with body: '[method_code]'"
   

Step Type: MODIFY (Change Existing Symbol)

1. Get Current State

   # Note: Main session calls Serena MCP directly
   Prompt: "Use find_symbol for '[symbol]' with include_body=true"
   

2. Replace Symbol Body

   # Note: Main session calls Serena MCP directly
   Prompt: "Use replace_symbol_body for '[symbol]' in '[file]' with new body: '[new_code]'"
   

3. Verify Modification

   • Compare new state with expected
   • Check for syntax errors

---

Import Management

Import Detection

1. Analyze Required Imports

   • From step.imports in plan
   • From code references

2. Check Existing Imports

   # Note: Main session calls Serena MCP directly
   Prompt: "Use get_symbols_overview for '[file]' to see import structure"
   

3. Add Missing Imports

   • Group by type (external, internal, local)
   • Maintain existing order convention

Import Insertion Strategy

ImportStrategy:
  external_first: boolean
  group_by_package: boolean
  sort_alphabetically: boolean
  newline_between_groups: boolean

---

Error Handling

Syntax Error Recovery

If Serena reports syntax error after injection:

1. Capture Error

   • Note exact error message
   • Identify problematic line

2. Attempt Auto-Fix

   • Common issues: missing semicolon, bracket mismatch
   • Try to fix automatically

3. Rollback if Needed

   # Note: Main session calls Serena MCP directly
   Prompt: "Use replace_content in '[file]' to restore: '[original_content]'"
   

Symbol Conflict

If symbol already exists:

1. Report Conflict

   • Show existing symbol details
   • Ask for resolution

2. Resolution Options

   • Rename new symbol
   • Merge with existing
   • Skip this step

File Not Found

If target file doesn't exist:

1. For Insert: Create file first, then insert
2. For Modify: Error - cannot modify non-existent file

---

Post-Injection Verification

Syntax Check

# Language-specific syntax validation
# TypeScript
npx tsc --noEmit [file]

# Python
python -m py_compile [file]

# Go
go build -n [file]

Symbol Verification

# Note: Main session calls Serena MCP directly
Prompt: "Use find_symbol for each injected symbol to verify existence"

Reference Verification

Check that references are valid:

# Note: Main session calls Serena MCP directly
Prompt: "Use find_referencing_symbols for '[new_symbol]' to verify it's reachable"

---

Knowledge Graph Update

After successful injection:

1. Update Memory

   # Note: Main session calls Serena MCP directly
   Prompt: "Use read_memory 'project-knowledge-graph.md', add new symbols, then write_memory to update"
   

2. Update Content

   • Add new symbols to symbol registry
   • Update dependency graph
   • Note new patterns if applicable

---

Dry Run Mode

When dry_run=true:

1. Show Planned Changes

   ## Dry Run Results
   
   ### Step 1: [action] [symbol]
   Would [create/insert/modify] in [file]:
   ```[language]
   [code preview]
   

   Step 2: ...

2. Validate Without Executing

   • Check all anchors exist
   • Verify no conflicts
   • Confirm imports are available

3. Return Simulation Results

   {
     "status": "simulation_complete",
     "steps_validated": 3,
     "potential_issues": [],
     "ready_to_execute": true
   }
   

---

Response Format

Success Response

{
  "status": "success",
  "steps_executed": 3,
  "files_modified": ["file1.ts", "file2.ts"],
  "symbols_created": ["NewService", "handleAction"],
  "symbols_modified": [],
  "knowledge_graph_updated": true,
  "warnings": []
}

Partial Success Response

{
  "status": "partial",
  "steps_executed": 2,
  "steps_failed": 1,
  "failed_step": {
    "order": 3,
    "error": "Symbol conflict",
    "resolution_needed": true
  },
  "rollback_performed": false
}

Error Response

{
  "status": "error",
  "error": "Anchor symbol not found",
  "step": 1,
  "rollback_performed": true,
  "files_restored": ["file1.ts"]
}

---

Execution Report

After completion, generate report:

# Injection Execution Report

## Summary

| Metric | Value |
|--------|-------|
| Steps Planned | X |
| Steps Executed | Y |
| Files Modified | Z |
| Symbols Created | N |
| Errors | M |

## Execution Details

### Step 1: CREATE NewService
- File: src/services/NewService.ts
- Status: SUCCESS
- Time: 1.2s

### Step 2: INSERT handleAction
- File: src/handlers/index.ts
- Anchor: handleOther
- Status: SUCCESS
- Time: 0.8s

## Verification Results

- [x] Syntax check passed
- [x] All symbols found
- [x] No broken references
- [x] Knowledge graph updated

## Next Steps

1. Run tests: `npm test`
2. Review changes: `git diff`
3. Commit if satisfied: `git add . && git commit -m "Add [feature]"`