Package fmtz extends the standard library fmt with additional functions.

go get -u ezpkg.io/[email protected]

The stdlib fmt.State provides many functions that always return nil error. They have their counterparts as fmtz.State that eliminate the need of error handling. There is also fmtz.MustState that panics on error, which is useful when other types implement fmt.State that may return non-nil error.

type Code struct {
    Char   rune
    Number int
}

func (c Code) Format(s0 fmt.State, r rune) {
    s := fmtz.WrapState(s0)
    s.WriteRuneZ(c.Char)
    s.Print(c.Number)
}

func main() {
    c := Code{'Ω', 123}
    fmt.Printf("%v", c)
}

fmtz.FormatMsgArgs is a helper function that formats a message with arguments. It is useful for using in logging and error messages.

func validate(err error, msgAndArgs ...any) error {
    if err == nil {
		return nil
    }
	msg := fmtz.FormatMsgArgs(msgAndArgs...)
	return typez.If(msg == "", err, fmt.Errorf("%v: %w", msg, err))
}

func main() {
    someError := errors.New("something went wrong")
    err := validate(someError, "failed to do something foo=%v bar=%v", "10", "20")
    fmt.Println(err)
	// Output: failed to do something foo=10 bar=20: something went wrong
}

As I work on various Go projects, I often find myself creating utility functions, extending existing packages, or developing packages to solve specific problems. Moving from one project to another, I usually have to copy or rewrite these solutions. So I created this repository to have all these utilities and packages in one place. Hopefully, you'll find them useful as well.

For more information, see the main repository.