decimalnonassign

Go linter that checks if the result of a decimal operation is assigned

supported package: https://pkg.go.dev/github.com/shopspring/decimal

Motivation

The arithmetic methods in github.com/shopspring/decimal are immutable. The result must therefore be assigned to a variable. If no assignment is made, unexpected situations are more likely to occur.

func sample() decimal.Decimal {
  result := decimal.Zero
  result = result.Add(decimal.NewFromFloat(2)) // ok
  result.Add(decimal.NewFromFloat(1)) // oops, Value not updated...💀

  return result
}

Usage

package main

import "github.com/shopspring/decimal"

func calledDecimalMethodInRange() {
	ds := []decimal.Decimal{decimal.NewFromFloat(2), decimal.NewFromFloat(2), decimal.NewFromFloat(2)}

	result := decimal.Zero
	for _, d := range ds {
		result = result.Add(d)
		result.Add(d)
	}
}

Analysis

$ decimalnoassign ./...
./a.go:11:10: The result of 'Add' is not assigned

Installation

go install github.com/sho-hata/decimalnonassign/cmd/decimalnonassign@latest

Contribution

1. Fork (https://github.com/sho-hata/decimalnonassign/fork)
2. Create a feature branch
3. Commit your changes
4. Rebase your local changes against the master branch
5. Run test suite with the go test ./... command and confirm that it passes
6. Run gofmt -s
7. Create new Pull Request

License

MIT

Author

sho-hata