Quick Start

Your First Analysis

Let’s run your first similarity analysis on a Go project. We’ll use a simple example to demonstrate the basic functionality.

Step 1: Prepare a Test Project

Create a simple Go project with some duplicate code:

mkdir test-project
cd test-project
go mod init test-project

Create a file duplicate.go:

package main

import "fmt"

func processUserDataV1(name string, age int) {
    if name == "" {
        fmt.Println("Name is required")
        return
    }
    if age < 0 {
        fmt.Println("Age must be positive")
        return
    }
    fmt.Printf("Processing user: %s, age: %d\n", name, age)
}

func processUserDataV2(username string, userAge int) {
    if username == "" {
        fmt.Println("Name is required")
        return
    }
    if userAge < 0 {
        fmt.Println("Age must be positive")
        return
    }
    fmt.Printf("Processing user: %s, age: %d\n", username, userAge)
}

func main() {
    processUserDataV1("Alice", 25)
    processUserDataV2("Bob", 30)
}

Step 2: Run Basic Analysis

Run similarity-go on your test project:

./bin/similarity-go ./

You should see output similar to:

🔍 Analyzing Go files in: ./
📊 Found 2 similar functions with 85% similarity

Function Similarity Report
==========================

📄 File: duplicate.go
🔗 Similar Functions:
  • processUserDataV1 (lines 5-15)
  • processUserDataV2 (lines 17-27)

📈 Similarity Score: 85.7%
📋 Differences:
  • Parameter names: name/username, age/userAge
  • Function names: processUserDataV1/processUserDataV2

💡 Suggestion: Consider refactoring to use a single function

Step 3: Adjust Similarity Threshold

You can adjust the sensitivity by changing the similarity threshold:

# Only show similarities above 90%
./bin/similarity-go --threshold 0.9 ./

# Show more similarities (above 70%)
./bin/similarity-go --threshold 0.7 ./

Step 4: Output Formats

similarity-go supports multiple output formats:

# JSON output for programmatic processing
./bin/similarity-go --format json ./

# YAML output
./bin/similarity-go --format yaml ./

# Detailed human-readable output (default)
./bin/similarity-go ./

Common Use Cases

Analyzing Specific Directories

# Analyze only the src directory
./bin/similarity-go ./src

# Analyze multiple directories
./bin/similarity-go ./cmd ./internal ./pkg

Excluding Files and Directories

# Use with custom workers and verbose output
./bin/similarity-go --workers 4 --verbose ./

Integration with CI/CD

Add similarity checking to your CI pipeline:

# GitHub Actions example
- name: Check code similarity
  run: |
    ./bin/similarity-go --threshold 0.8 --format json ./ > similarity-report.json
    if [ -s similarity-report.json ]; then
      echo "High similarity detected, consider refactoring"
      exit 1
    fi

Understanding the Output

similarity-go provides several key metrics:

• Similarity Score: Percentage indicating how similar two functions are
• Line Numbers: Exact location of similar code blocks
• Differences: What makes the functions different
• Suggestions: Recommendations for refactoring

Configuration File

For complex projects, create a .similarity-go.yaml configuration file:

For more advanced configuration, you can create a configuration file, but the current version primarily uses command-line flags.

./bin/similarity-go --threshold 0.8 --format json --workers 8 ./

Next Steps

Now that you’re familiar with the basics:

1. Explore CLI Commands for advanced options
2. Learn about Configuration for complex projects
3. Understand the AST Analysis algorithms
4. Check out Integration Examples