diff options
Diffstat (limited to 'flag.go')
| -rw-r--r-- | flag.go | 34 |
1 files changed, 34 insertions, 0 deletions
@@ -7,6 +7,7 @@ import ( "flag" "fmt" "os" + "sort" "strconv" "strings" "sync/atomic" @@ -144,11 +145,44 @@ func (f *Feature) String() string { // value or an error. type ParseFunc[T any] func(string) (T, error) +// ParseStringEnum returns a ParseFunc that will return the string +// passed if it matched any of the values supplied. If no such match is +// found, an UnknownEnumValueError is returned. +// +// Note that unlike ParseProtobufEnum, comparison is case-sensitive. +func ParseStringEnum(values ...string) ParseFunc[string] { + return func(s string) (string, error) { + for _, val := range values { + if s == val { + return s, nil + } + } + return "", UnknownEnumValueError{s, values} + } +} + // ParseTime parses a string according to the time.RFC3339 format. func ParseTime(s string) (time.Time, error) { return time.Parse(time.RFC3339, s) } +// UnknownEnumValueError is returned by the functions produced by +// ParseProtobufEnum and ParseStringEnum when an unknown value is +// encountered. +type UnknownEnumValueError struct { + Actual string + Expected []string +} + +func (err UnknownEnumValueError) Error() string { + // We sort the expected values so the output is deterministic, which may + // be useful when parsing logs or otherwise examining program output. + if !sort.StringsAreSorted(err.Expected) { + sort.Strings(err.Expected) + } + return fmt.Sprintf("unknown value %s, expected one of %s", err.Actual, err.Expected) +} + type flagFeature struct{ *Feature } func (flagFeature) IsBoolFlag() bool { return true } |