Rust Call Graph

Visualize function call relationships using LSP call hierarchy.

Usage

/rust-call-graph <function_name> [--depth N] [--direction in|out|both]

Options:

• --depth N: How many levels to traverse (default: 3)
• --direction: in (callers), out (callees), both

Examples:

• /rust-call-graph process_request - Show both callers and callees
• /rust-call-graph handle_error --direction in - Show only callers
• /rust-call-graph main --direction out --depth 5 - Deep callee analysis

LSP Operations

1. Prepare Call Hierarchy

Get the call hierarchy item for a function.

LSP(
  operation: "prepareCallHierarchy",
  filePath: "src/handler.rs",
  line: 45,
  character: 8
)

2. Incoming Calls (Who calls this?)

LSP(
  operation: "incomingCalls",
  filePath: "src/handler.rs",
  line: 45,
  character: 8
)

3. Outgoing Calls (What does this call?)

LSP(
  operation: "outgoingCalls",
  filePath: "src/handler.rs",
  line: 45,
  character: 8
)

Workflow

User: "Show call graph for process_request"
    │
    ▼
[1] Find function location
    LSP(workspaceSymbol) or Grep
    │
    ▼
[2] Prepare call hierarchy
    LSP(prepareCallHierarchy)
    │
    ▼
[3] Get incoming calls (callers)
    LSP(incomingCalls)
    │
    ▼
[4] Get outgoing calls (callees)
    LSP(outgoingCalls)
    │
    ▼
[5] Recursively expand to depth N
    │
    ▼
[6] Generate ASCII visualization

Output Format

Incoming Calls (Who calls this?)

## Callers of `process_request`

main
└── run_server
    └── handle_connection
        └── process_request  ◄── YOU ARE HERE

Outgoing Calls (What does this call?)

## Callees of `process_request`

process_request  ◄── YOU ARE HERE
├── parse_headers
│   └── validate_header
├── authenticate
│   ├── check_token
│   └── load_user
├── execute_handler
│   └── [dynamic dispatch]
└── send_response
    └── serialize_body

Bidirectional (Both)

## Call Graph for `process_request`

                    ┌─────────────────┐
                    │      main       │
                    └────────┬────────┘
                             │
                    ┌────────▼────────┐
                    │   run_server    │
                    └────────┬────────┘
                             │
                    ┌────────▼────────┐
                    │handle_connection│
                    └────────┬────────┘
                             │
        ┌────────────────────┼────────────────────┐
        │                    │                    │
┌───────▼───────┐   ┌───────▼───────┐   ┌───────▼───────┐
│ parse_headers │   │ authenticate  │   │send_response  │
└───────────────┘   └───────┬───────┘   └───────────────┘
                            │
                    ┌───────┴───────┐
                    │               │
             ┌──────▼──────┐ ┌──────▼──────┐
             │ check_token │ │  load_user  │
             └─────────────┘ └─────────────┘

Analysis Insights

After generating the call graph, provide insights:

## Analysis

**Entry Points:** main, test_process_request
**Leaf Functions:** validate_header, serialize_body
**Hot Path:** main → run_server → handle_connection → process_request
**Complexity:** 12 functions, 3 levels deep

**Potential Issues:**
- `authenticate` has high fan-out (4 callees)
- `process_request` is called from 3 places (consider if this is intentional)

Common Patterns

User Says	Direction	Use Case
"Who calls X?"	incoming	Impact analysis
"What does X call?"	outgoing	Understanding implementation
"Show call graph"	both	Full picture
"Trace from main to X"	outgoing	Execution path

Visualization Options

Style	Best For
Tree (default)	Simple hierarchies
Box diagram	Complex relationships
Flat list	Many connections
Mermaid	Export to docs

Mermaid Export

graph TD
    main --> run_server
    run_server --> handle_connection
    handle_connection --> process_request
    process_request --> parse_headers
    process_request --> authenticate
    process_request --> send_response

Related Skills

When	See
Find definition	rust-code-navigator
Project structure	rust-symbol-analyzer
Trait implementations	rust-trait-explorer
Safe refactoring	rust-refactor-helper