find-complexity

Find Complexity Hotspots

Identify Go functions that are hard to review, test, and maintain.

Rules

• Report findings, do not refactor. Refactoring is a separate task.
• Focus on production code (internal/, api/, cmd/). Skip tests unless explicitly asked.
• Rank by severity: highest complexity first.

Step 1: Determine Scope

Ask the user:

• Branch mode: only files changed in the current branch vs main.
• Full mode: scan the entire codebase.

For branch mode:

git diff --name-only upstream/main -- 'internal/' 'api/' 'cmd/' | grep '\.go$' | grep -v '_test\.go$'

Step 2: Install Prerequisites

Install gocyclo and gocognit if not available:

go install github.com/fzipp/gocyclo/cmd/gocyclo@latest
go install github.com/uudashr/gocognit/cmd/gocognit@latest

Step 3: Cyclomatic Complexity

gocyclo -over 10 <target>

This shows functions with cyclomatic complexity over 10.

Thresholds: 1-10 (simple), 11-20 (moderate), 21-50 (complex), 51+ (untestable).

Step 4: Cognitive Complexity

Cognitive complexity weights nesting depth — a 5-deep if scores much higher than 5 sequential ifs.

gocognit -over 15 <target>

This shows functions with cognitive complexity over 15.

Step 5: Function Length

Find long functions (50+ lines of code, excluding comments and blank lines):

for file in $(find <target> -name '*.go' -not -name '*_test.go'); do
    awk '/^func / {start=NR; func=$0} 
         /^}/ && start {
           len=NR-start; 
           if(len>50) print FILENAME":"start": "func" ("len" lines)"
         }' "$file"
done

Step 6: Parameter Count

Find functions with too many parameters (6+):

rg "^func.*\([^)]{60,}\)" <target> -A 0

Functions with 6+ parameters are candidates for parameter objects or config structs.

Step 7: File Size

Find large files (500+ lines):

wc -l $(find <target> -name '*.go' -not -name '*_test.go') | sort -rn | head -20

Files over 500 lines are candidates for splitting into focused packages.

Step 8: Classify Findings

For each function found, classify:

Step 9: Report

For each finding:

1. File, function name, line number
2. Cyclomatic/cognitive complexity score
3. Lines of code / parameter count
4. Classification (split / simplify / parameterize / monitor)
5. Brief suggestion

Summary: total hotspots, top 5 worst offenders, estimated refactoring effort.