crap4clj

name	crap4clj
description	Calculates cyclomatic complexity and CRAP scores for Clojure functions by combining complexity analysis with Cloverage test coverage data, generating sorted reports that identify high-risk under-tested code. Use when the user asks for a CRAP report, cyclomatic complexity analysis, or code quality metrics on a Clojure project.

crap4clj — CRAP Metric for Clojure

Computes the CRAP (Change Risk Anti-Pattern) score for every defn and defn- in a Clojure project. CRAP combines cyclomatic complexity with test coverage to identify functions that are both complex and under-tested.

Setup

Add both a :cov alias (Cloverage) and a :crap alias to the project's deps.edn:

:cov  {:extra-deps {cloverage/cloverage {:mvn/version "1.2.4"}}
       :main-opts ["-m" "speclj.cloverage" "--" "-p" "src" "-s" "spec"]}
:crap {:extra-deps {io.github.unclebob/crap4clj
                     {:git/url "https://github.com/unclebob/crap4clj"
                      :git/sha "<current-sha>"}}
       :main-opts ["-m" "crap4clj.core"]}

The example above uses speclj.cloverage as the runner. For clojure.test projects, use cloverage.coverage instead:

:cov  {:extra-deps {cloverage/cloverage {:mvn/version "1.2.4"}}
       :main-opts ["-m" "cloverage.coverage" "-p" "src" "-s" "test"]}

Adjust the -p (source path) and -s (test path) flags in :cov to match your project layout.

Usage

# First verify Cloverage works on its own
clj -M:cov

# Analyze all source files under src/
clj -M:crap

# Filter to specific modules
clj -M:crap combat movement

crap4clj automatically deletes stale coverage reports, runs clj -M:cov, and then analyzes the results.

Output

A table sorted by CRAP score (worst first):

CRAP Report
===========
Function                       Namespace                            CC   Cov%     CRAP
-------------------------------------------------------------------------------------
complex-fn                     my.namespace                         12   45.0%    130.2
simple-fn                      my.namespace                          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 Cloverage (clj -M:cov)
2. Finds all .clj and .cljc files under src/
3. Extracts defn/defn- functions with line ranges
4. Computes cyclomatic complexity (if/when/cond/condp/case/cond->/cond->>/some->/some->>/and/or/loop/catch)
5. Reads Cloverage HTML for per-line form coverage
6. Applies CRAP formula: CC² × (1 - cov)³ + CC
7. Sorts by CRAP score descending and prints report

Troubleshooting

• Cloverage fails to run: Verify :cov alias paths match your project layout — -p should point to your source root and -s to your test root.
• All coverage shows 0%: Ensure clj -M:cov runs successfully on its own before running :crap. Check that test files are found under the specified test path.
• Functions show N/A coverage: This occurs with split-file namespace patterns (in-ns + load). Add --lcov to your :cov alias main-opts for accurate per-file coverage.