How to Preserve Argument Integrity in Formatted Errors?

Preserving the Integrity of Multiple Arguments in Formatted Errors

To implement a custom version of errors.New that allows for variable-argument formatting, we encounter a technical challenge. As the provided code showcases:

<code class="go">func NewError(format string, a ...interface{}) error {
    return errors.New(fmt.Sprintf(format, a))
}</code>

The ...a parameter unintentionally merges into a single array during method invocation, leading to incorrect formatting. The solution lies in emulating the functionality of fmt.Errorf, as seen in its source code:

<code class="go">func Errorf(format string, a ...interface{}) error {
    return errors.New(Sprintf(format, a...))
}</code>

Notice that the ... operator follows a after the parameter list. In Go, this syntax enables the passing of arguments as separate values rather than a single merged array. The specification outlines this behavior:

If the final argument is assignable to a slice type []T, it may be passed unchanged as the value for a ...T parameter if the argument is followed by ....

By incorporating the ... operator as seen in fmt.Errorf, we ensure that multiple arguments retain their individuality during formatting, resulting in the desired behavior:

<code class="go">func NewError(format string, a ...interface{}) error {
    return errors.New(fmt.Sprintf(format, a...))
}</code>

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