Clean Unused Code

Overview

This skill provides workflows for finding and removing unused code in projects. It uses static analysis tools to identify unreachable functions and dead code.

When to Use

Use this skill when:

• Cleaning up dead code in a project
• Removing unreachable functions
• Optimizing codebase size
• Preparing for code review or release

Supported Languages

Language	Tool	Install Command
golang	deadcode	go install golang.org/x/tools/cmd/deadcode@latest

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Golang Projects

Prerequisites

Install the deadcode tool:

go install golang.org/x/tools/cmd/deadcode@latest

Step 1: Find Unused Code

Run deadcode from the project root:

deadcode ./...

For projects with test dependencies, include tests:

deadcode -test ./...

Step 2: Parse Output

The output format is:

<file>:<line>:<column>: unreachable func: <function_name>

Example output:

internal/utils/helper.go:45:1: unreachable func: unusedHelper
pkg/service/old.go:12:1: unreachable func: deprecatedMethod

Step 3: Review and Remove

For each unreachable function:

1. Verify it is safe to remove (not called via reflection, not an interface implementation)
2. Remove the function definition
3. Remove any related imports that become unused
4. Run go build ./... to verify no build errors

Step 4: Clean Up Imports

After removing functions, clean up unused imports:

goimports -w .

Or use gopls organize imports functionality.

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Caveats

[!WARNING] deadcode may not detect functions called via:

• Reflection (reflect.ValueOf().MethodByName())
• Interface implementations used through dependency injection
• CGo bindings
• Plugin systems

When to Skip Removal

Do NOT remove functions if:

• They implement an interface (even if not directly called)
• They are exported and part of a public API/library
• They are called via reflection
• They are test helpers used in _test.go files (use -test flag)

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Verification

After cleaning, verify the project:

# Build check
go build ./...

# Test check
go test ./...

# Run deadcode again to confirm
deadcode ./...