diff options
Diffstat (limited to 'src/flag/flag.go')
| -rw-r--r-- | src/flag/flag.go | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/src/flag/flag.go b/src/flag/flag.go index 323e452a8..56860fc9d 100644 --- a/src/flag/flag.go +++ b/src/flag/flag.go @@ -235,6 +235,9 @@ func (d *durationValue) String() string { return (*time.Duration)(d).String() } // If a Value has an IsBoolFlag() bool method returning true, // the command-line parser makes -name equivalent to -name=true // rather than using the next command-line argument. +// +// It is the implementer's responsibility to verify, if required, that the +// flag has been set only once. type Value interface { String() string Set(string) error @@ -270,6 +273,7 @@ type FlagSet struct { parsed bool actual map[string]*Flag formal map[string]*Flag + set map[*Flag]bool args []string // arguments after flags errorHandling ErrorHandling output io.Writer // nil means stderr; use out() accessor @@ -717,6 +721,25 @@ func (f *FlagSet) usage() { } } +// alreadySet reports whether the flag has already been set during parsing. +// Because user-defined flags may legally be set multiple times, it only +// complains about flags defined in this package. +func (f *FlagSet) alreadySet(flag *Flag) bool { + if f.set == nil { + f.set = make(map[*Flag]bool) + } + switch flag.Value.(type) { + case *boolValue, *intValue, *int64Value, *uintValue, *uint64Value, *stringValue, *float64Value, *durationValue: + default: + return false // Not one of ours. + } + if f.set[flag] { + return true + } + f.set[flag] = true + return false +} + // parseOne parses one flag. It reports whether a flag was seen. func (f *FlagSet) parseOne() (bool, error) { if len(f.args) == 0 { @@ -760,6 +783,12 @@ func (f *FlagSet) parseOne() (bool, error) { } return false, f.failf("flag provided but not defined: -%s", name) } + + // has it already been set? + if f.alreadySet(flag) { + return false, f.failf("flag set multiple times: -%s", name) + } + if fv, ok := flag.Value.(boolFlag); ok && fv.IsBoolFlag() { // special case: doesn't need an arg if has_value { if err := fv.Set(value); err != nil { @@ -795,6 +824,7 @@ func (f *FlagSet) parseOne() (bool, error) { // The return value will be ErrHelp if -help or -h were set but not defined. func (f *FlagSet) Parse(arguments []string) error { f.parsed = true + f.set = nil f.args = arguments for { seen, err := f.parseOne() |