func parseReplace()

in modfile/rule.go [462:537]
73 lines of code
18 McCabe index (conditional complexity)

func parseReplace(filename string, line *Line, verb string, args []string, fix VersionFixer) (*Replace, *Error) {
	wrapModPathError := func(modPath string, err error) *Error {
		return &Error{
			Filename: filename,
			Pos:      line.Start,
			ModPath:  modPath,
			Verb:     verb,
			Err:      err,
		}
	}
	wrapError := func(err error) *Error {
		return &Error{
			Filename: filename,
			Pos:      line.Start,
			Err:      err,
		}
	}
	errorf := func(format string, args ...interface{}) *Error {
		return wrapError(fmt.Errorf(format, args...))
	}

	arrow := 2
	if len(args) >= 2 && args[1] == "=>" {
		arrow = 1
	}
	if len(args) < arrow+2 || len(args) > arrow+3 || args[arrow] != "=>" {
		return nil, errorf("usage: %s module/path [v1.2.3] => other/module v1.4\n\t or %s module/path [v1.2.3] => ../local/directory", verb, verb)
	}
	s, err := parseString(&args[0])
	if err != nil {
		return nil, errorf("invalid quoted string: %v", err)
	}
	pathMajor, err := modulePathMajor(s)
	if err != nil {
		return nil, wrapModPathError(s, err)

	}
	var v string
	if arrow == 2 {
		v, err = parseVersion(verb, s, &args[1], fix)
		if err != nil {
			return nil, wrapError(err)
		}
		if err := module.CheckPathMajor(v, pathMajor); err != nil {
			return nil, wrapModPathError(s, err)
		}
	}
	ns, err := parseString(&args[arrow+1])
	if err != nil {
		return nil, errorf("invalid quoted string: %v", err)
	}
	nv := ""
	if len(args) == arrow+2 {
		if !IsDirectoryPath(ns) {
			return nil, errorf("replacement module without version must be directory path (rooted or starting with ./ or ../)")
		}
		if filepath.Separator == '/' && strings.Contains(ns, `\`) {
			return nil, errorf("replacement directory appears to be Windows path (on a non-windows system)")
		}
	}
	if len(args) == arrow+3 {
		nv, err = parseVersion(verb, ns, &args[arrow+2], fix)
		if err != nil {
			return nil, wrapError(err)
		}
		if IsDirectoryPath(ns) {
			return nil, errorf("replacement module directory path %q cannot have version", ns)

		}
	}
	return &Replace{
		Old:    module.Version{Path: s, Version: v},
		New:    module.Version{Path: ns, Version: nv},
		Syntax: line,
	}, nil
}