Grepai Trace Callers

# GrepAI Trace Callers

This skill covers using `grepai trace callers` to find all code locations that call a specific function or method.

## When to Use This Skill

- Finding all usages of a function before refactoring
- Understanding function dependencies
- Impact analysis before changes
- Code navigation and exploration

## What is Trace Callers?

`grepai trace callers` answers: **"Who calls this function?"**

```
func Login(user, pass) {...}
        ↑
        │
┌───────┴───────────────────┐
│   Who calls Login()?      │
├───────────────────────────┤
│ • HandleAuth (auth.go:42) │
│ • TestLogin (test.go:15)  │
│ • CLI (main.go:88)        │
└───────────────────────────┘
```

## Basic Usage

```bash
grepai trace callers "FunctionName"
```

### Example

```bash
grepai trace callers "Login"
```

Output:
```
🔍 Callers of "Login"

Found 3 callers:

1. HandleAuth
   File: handlers/auth.go:42
   Context: user.Login(ctx, credentials)

2. TestLoginSuccess
   File: handlers/auth_test.go:15
   Context: result := Login(testUser, testPass)

3. RunCLI
   File: cmd/main.go:88
   Context: err := auth.Login(username, password)
```

## JSON Output

For programmatic use:

```bash
grepai trace callers "Login" --json
```

Output:
```json
{
  "query": "Login",
  "mode": "callers",
  "count": 3,
  "results": [
    {
      "file": "handlers/auth.go",
      "line": 42,
      "caller": "HandleAuth",
      "context": "user.Login(ctx, credentials)"
    },
    {
      "file": "handlers/auth_test.go",
      "line": 15,
      "caller": "TestLoginSuccess",
      "context": "result := Login(testUser, testPass)"
    },
    {
      "file": "cmd/main.go",
      "line": 88,
      "caller": "RunCLI",
      "context": "err := auth.Login(username, password)"
    }
  ]
}
```

## Compact JSON (AI Optimized)

```bash
grepai trace callers "Login" --json --compact
```

Output:
```json
{
  "q": "Login",
  "m": "callers",
  "c": 3,
  "r": [
    {"f": "handlers/auth.go", "l": 42, "fn": "HandleAuth"},
    {"f": "handlers/auth_test.go", "l": 15, "fn": "TestLoginSuccess"},
    {"f": "cmd/main.go", "l": 88, "fn": "RunCLI"}
  ]
}
```

## TOON Output (v0.26.0+)

TOON format offers ~50% fewer tokens than JSON:

```bash
grepai trace callers "Login" --toon
```

Output:
```
callers[3]:
  - call_site:
      context: "user.Login(ctx, credentials)"
      file: handlers/auth.go
      line: 42
    symbol:
      name: HandleAuth
      ...
```

> **Note:** `--json` and `--toon` are mutually exclusive.

## Extraction Modes

GrepAI offers two extraction modes:

### Fast Mode (Default)

Uses regex patterns. Fast and dependency-free.

```bash
grepai trace callers "Login" --mode fast
```

### Precise Mode

Uses tree-sitter AST parsing. More accurate but requires tree-sitter.

```bash
grepai trace callers "Login" --mode precise
```

### Comparison

| Mode | Speed | Accuracy | Dependencies |
|------|-------|----------|--------------|
| `fast` | ⚡⚡⚡ | Good | None |
| `precise` | ⚡⚡ | Excellent | tree-sitter |

## Configuration

Configure trace in `.grepai/config.yaml`:

```yaml
trace:
  mode: fast  # fast or precise

  enabled_languages:
    - .go
    - .js
    - .ts
    - .py
    - .php
    - .rs

  exclude_patterns:
    - "*_test.go"
    - "*.spec.ts"
```

## Supported Languages

| Language | Extensions |
|----------|------------|
| Go | `.go` |
| JavaScript | `.js`, `.jsx` |
| TypeScript | `.ts`, `.tsx` |
| Python | `.py` |
| PHP | `.php` |
| C/C++ | `.c`, `.h`, `.cpp`, `.hpp`, `.cc`, `.cxx` |
| Rust | `.rs` |
| Zig | `.zig` |
| C# | `.cs` |
| Java | `.java` |
| Pascal/Delphi | `.pas`, `.dpr` |

## Use Cases

### Before Refactoring

```bash
# Find all usages before renaming
grepai trace callers "getUserById"

# Check impact of changing signature
grepai trace callers "processPayment"
```

### Understanding Codebase

```bash
# Who uses this co