A simple LogPrint function for file/line chain/log wrapping and error testing

[Kevin Chadwick]

BSD license/public domain, Feel free to criticise/use
Means I can easily disable file/line inclusion if stdlib ever gets
that part of the error values proposal. Also easy to apply with
search/replace.

// LogPrint : An error wrapping log.Print replacement that adds location and
// file info to each link in the chain, without adding LOC.
// It utilises fmt.Errorf %w to create/preserve the original errors
// testing Operand.
//
// @ARGS :
/// testErr = nil, or an error type (any comparison operands will be preserved or applied)
// prepend = fmt.Sprint arguments to form a string that is prepended (any comparison operands will be lost)
//
// @RETURN :
// error with log Lshortfile equivalents prepended and optional test operands applied (Errorf Unwrap method)
//
// @NOTE :
// Any standard lib changes can be accommodated for by modifying
// this function
//
// Every chain should still be logged to avoid loss upon fatal exception.
// Wrapping simply preserves a self contained log chain line output plus
// any embedded operand for later errors.(As|Is) test cases...
func LogPrint(testErr error, prepend ...interface{}) error {
// Get the Location of this functions caller
_, fileName, fileLine, ok := runtime.Caller(1)
fileName = filepath.Base(fileName)

var s string
if ok == true {
s = fmt.Sprintf("%s:%d", fileName, fileLine)
} else {
s = "LogPrint: runtime.Caller(): failed"
}
// Accept arguments or interface just like fmt.Sprint
text := fmt.Sprint(prepend...)

// Only include an unwrap method when the user requests it.
if testErr != nil {
testErr = fmt.Errorf("%v: %v: %w: ", s, text, testErr)
} else {
testErr = fmt.Errorf("%v: %v: ", s, text)
}
log.Print(testErr.Error())
return testErr
}