GUY

Graphing Utility for Your code

Interactive control-flow graphs for Python, Java, PHP, C, Go, and Rust — directly in Visual Studio Code.

GUY turns source code into an interactive control-flow graph (CFG). Follow branches and loops, inspect complexity, explore independent execution paths, and jump from the graph back to the exact source range without leaving the editor.

All analysis runs locally. GUY uses bundled Tree-sitter WASM parsers and does not require a language runtime or send source code to an external service.

Why use GUY?

• Understand unfamiliar code: see decisions, loops, early returns, and exception paths at a glance.
• Focus the analysis: graph an entire file, the current selection, or only the function under the cursor.
• Connect graph and source: select nodes, edges, callables, or paths to highlight their corresponding code.
• Spot risky complexity: review node, edge, component, path, and cyclomatic-complexity metrics.
• Know when the model is partial: get a warning with source locations when GUY encounters control-flow syntax it does not model yet.
• Keep working while editing: the preview refreshes as the active source changes and can be locked or pinned when needed.

Getting started

1. Install GUY - Control Flow Graphs from the Extensions view.
2. Open a supported source file.
3. Open the Command Palette (Ctrl+Shift+P / Cmd+Shift+P) and run GUY: Generate CFG from File.
4. Click a graph item to navigate to and highlight its source code.

You can also use the branch icon in the editor title bar. To narrow the graph, right-click selected code and choose GUY: Generate CFG from Selection, or place the cursor inside a callable and choose GUY: Generate CFG from Current Function.

What the graph shows

• Statements and sequential execution flow.
• Decision branches for if/else-if/else and supported switch/match forms.
• Loop entry, body, continuation, and exit paths.
• Abrupt flow from return, break, continue, and exceptions.
• Callable boundaries and source ranges.
• Metrics for nodes, edges, decisions, connected components, independent paths, and cyclomatic complexity.
• Unsupported control-flow constructs, including their type, line, and source preview.

Use simplified mode to compact consecutive statements or detailed mode to inspect individual operations. The preview can switch between top-to-bottom and left-to-right layouts.

When Tree-sitter recognizes a construct whose control-flow semantics are not modeled yet, GUY keeps it visible as a regular statement and shows an Unsupported syntax warning. This prevents an opaque construct from being mistaken for fully modeled flow.

Supported languages

Language	Files	Core coverage
Python	.py	Functions, branches, loops, with, return, break, continue, raise, try/except/finally, and loop else
Java	.java	Methods, constructors, branches, classic/enhanced loops, jumps, and try/catch/finally/throw
PHP	.php	Functions, methods, branches, for/foreach/while, jumps, and exception flow
C	.c, .h*	Functions, branches, loops, return, break, and continue
Go	.go	Functions, methods, branches, loops, return, break, and continue
Rust	.rs	Functions, methods, branches, loops, return, break, and continue

* Header files are supported when VS Code identifies the document language as C.

GUY can recover a partial graph from many syntax errors. When parser recovery was required, the preview displays a diagnostic so you know the graph may be incomplete.

Commands

Command	Description
GUY: Generate CFG from File	Build a graph for the active supported file.
GUY: Generate CFG from Selection	Build a graph for the selected source range.
GUY: Generate CFG from Current Function	Build a graph for the function, method, or constructor containing the cursor.
GUY: Toggle Simplified/Detailed CFG View	Switch the current graph detail mode.

Settings

Setting	Default	Description
guy.autoOpenPreview	true	Open the CFG preview automatically after generation.
guy.graphLayout	top-bottom	Set the default direction to top-bottom or left-right.
guy.showMetricsPanel	true	Show graph metrics in the preview.
guy.highlightCodeOnNodeClick	true	Highlight source code when a graph item is selected.
guy.maxNodesBeforeWarning	100	Warn when a graph exceeds this number of nodes.
guy.highComplexityThreshold	10	Set the cyclomatic-complexity threshold for suggestions.

Requirements

• Visual Studio Code ^1.120.0.
• No Python, Java, PHP, C, Go, or Rust runtime is required for graph generation.

Current limitations

• Exception matching is type-agnostic, so exception edges represent possible handlers and a possible unhandled route.
• Syntax recovery can produce an incomplete graph.
• Independent paths are capped for very large graphs to keep the preview responsive.
• Unsupported language-specific constructs remain source-ranged statements and are listed in the preview until dedicated flow modeling and tests are added.

Development

The project uses Node.js 22, configured in mise.toml.

git clone https://github.com/gm64x/guy-vscode.git
cd guy-vscode
mise install
mise exec -- npm install
mise exec -- npm run compile

Press F5 in VS Code to launch an Extension Development Host. Useful validation commands are:

npm run check-types
npm run lint
npm run compile-tests
npm run compile
npm test

Create a production bundle with npm run package, or build an installable package with npm run package:vsix.

Adding another language

1. Install its official tree-sitter-* grammar package.
2. Create an adapter that converts grammar nodes to the neutral control-flow IR.
3. Register its metadata, extension rules, display name, and VS Code language ID.
4. Enable its editor menu conditions.
5. Add real WASM-backed fixtures for file, selection, and callable modes.

The shared CFG builder and automatic WASM asset discovery do not need language-specific branches.

Help and feedback

• Ask a question or share an idea
• Report a bug or request a feature
• Read the contribution guide
• Review release changes
• Browse the source code