crap4go

name	crap4go
description	Use when the user asks for a CRAP report, cyclomatic complexity analysis, or code quality metrics on a Go project

crap4go - CRAP Metric for Go

Computes the CRAP (Change Risk Anti-Pattern) score for every Go function and method. CRAP combines cyclomatic complexity with test coverage to identify functions that are both complex and under-tested.

Setup

Run from the root of a Go module:

go run github.com/unclebob/crap4go/cmd/crap4go@latest

Or install it:

go install github.com/unclebob/crap4go/cmd/crap4go@latest
crap4go

Usage

# Analyze all non-test Go source files under the module
crap4go

# Filter to specific path fragments
crap4go internal/combat movement

crap4go automatically deletes old coverage reports, runs go test ./... -coverprofile=target/coverage/coverage.out, and then analyzes the results.

Output

A table sorted by CRAP score, worst first:

CRAP Report
===========
Function                       Package                               CC   Cov%     CRAP
-------------------------------------------------------------------------------------
Widget.Run                     widget                                12   45.0%    130.2
simple                         widget                                 1  100.0%      1.0

Interpreting Scores

CRAP Score	Meaning
1-5	Clean - low complexity, well tested
5-30	Moderate - consider refactoring or adding tests
30+	Crappy - high complexity with poor coverage

How It Works

1. Deletes old coverage reports and runs Go coverage
2. Finds non-test .go files, excluding .git, target, and vendor
3. Extracts functions and methods with line ranges
4. Computes cyclomatic complexity (if, for, range, switch cases, select clauses, &&, ||)
5. Reads Go coverage profile segments for per-function statement coverage
6. Applies CRAP formula: CC² x (1 - cov)³ + CC
7. Sorts by CRAP score descending and prints report