taler-mailbox

getopt.go (12337B)

---

 // Copyright 2017 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // Package getopt parses command lines using getopt(3) syntax.
 // It is a replacement for flag.Parse but still expects flags themselves
 // to be defined in package flag.
 //
 // Flags defined with one-letter names are available as short flags
 // (invoked using one dash, as in -x) and all flags are available as
 // long flags (invoked using two dashes, as in --x or --xylophone).
 //
 // To use, define flags as usual with package flag. Then introduce
 // any aliases by calling getopt.Alias:
 //
 //	getopt.Alias("n", "dry-run")
 //	getopt.Alias("v", "verbose")
 //
 // Or call getopt.Aliases to define a list of aliases:
 //
 //	getopt.Aliases(
 //		"n", "dry-run",
 //		"v", "verbose",
 //	)
 //
 // One name in each pair must already be defined in package flag
 // (so either "n" or "dry-run", and also either "v" or "verbose").
 //
 // Then parse the command-line:
 //
 //	getopt.Parse()
 //
 // If it encounters an error, Parse calls flag.Usage and then exits the program.
 //
 // When writing a custom flag.Usage function, call getopt.PrintDefaults
 // instead of flag.PrintDefaults to get a usage message that includes the
 // names of aliases in flag descriptions.
 //
 // At initialization time, this package installs a new flag.Usage that is the
 // same as the default flag.Usage except that it calls getopt.PrintDefaults
 // instead of flag.PrintDefaults.
 //
 // This package also defines a FlagSet wrapping the standard flag.FlagSet.
 //
 // Caveat
 //
 // In general Go flag parsing is preferred for new programs, because
 // it is not as pedantic about the number of dashes used to invoke
 // a flag (you can write -verbose or --verbose and the program
 // does not care). This package is meant to be used in situations
 // where, for legacy reasons, it is important to use exactly getopt(3)
 // syntax, such as when rewriting in Go an existing tool that already
 // uses getopt(3).
 package getopt // import "rsc.io/getopt"
 
 import (
 	"flag"
 	"fmt"
 	"io"
 	"os"
 	"reflect"
 	"strings"
 	"unicode/utf8"
 )
 
 func init() {
 	flag.Usage = func() {
 		fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
 		PrintDefaults() // ours not package flag's
 	}
 
 	CommandLine.FlagSet = flag.CommandLine
 	CommandLine.name = os.Args[0]
 	CommandLine.errorHandling = flag.ExitOnError
 	CommandLine.outw = os.Stderr
 	CommandLine.Usage = func() { flag.Usage() }
 }
 
 var CommandLine FlagSet
 
 // A FlagSet is a set of defined flags.
 // It wraps and provides the same interface as flag.FlagSet
 // but parses command line arguments using getopt syntax.
 //
 // Note that "go doc" shows only the methods customized
 // by package getopt; FlagSet also provides all the methods
 // of the embedded flag.FlagSet, like Bool, Int, NArg, and so on.
 type FlagSet struct {
 	*flag.FlagSet
 
 	alias         map[string]string
 	unalias       map[string]string
 	name          string
 	errorHandling flag.ErrorHandling
 	outw          io.Writer
 }
 
 func (f *FlagSet) out() io.Writer {
 	if f.outw == nil {
 		return os.Stderr
 	}
 	return f.outw
 }
 
 // SetOutput sets the destination for usage and error messages.
 // If output is nil, os.Stderr is used.
 func (f *FlagSet) SetOutput(output io.Writer) {
 	f.FlagSet.SetOutput(output)
 	f.outw = output
 }
 
 // NewFlagSet returns a new, empty flag set with the specified name and error
 // handling property.
 func NewFlagSet(name string, errorHandling flag.ErrorHandling) *FlagSet {
 	f := new(FlagSet)
 	f.Init(name, errorHandling)
 	return f
 }
 
 // Init sets the name and error handling proprety for a flag set.
 func (f *FlagSet) Init(name string, errorHandling flag.ErrorHandling) {
 	if f.FlagSet == nil {
 		f.FlagSet = new(flag.FlagSet)
 	}
 	f.FlagSet.Init(name, errorHandling)
 	f.name = name
 	f.errorHandling = errorHandling
 	f.FlagSet.Usage = f.defaultUsage
 }
 
 func (f *FlagSet) init() {
 	if f.alias == nil {
 		f.alias = make(map[string]string)
 		f.unalias = make(map[string]string)
 	}
 }
 
 // Lookup returns the Flag structure of the named flag,
 // returning nil if none exists.
 // If name is a defined alias for a defined flag,
 // Lookup returns the original flag; in this case
 // the Name field in the result will differ from the
 // name passed to Lookup.
 func (f *FlagSet) Lookup(name string) *flag.Flag {
 	if x, ok := f.alias[name]; ok {
 		name = x
 	}
 	return f.FlagSet.Lookup(name)
 }
 
 // Alias introduces an alias for an existing flag name.
 // The short name must be a single letter, and the long name must be multiple letters.
 // Exactly one name must be defined as a flag already: the undefined name is introduced
 // as an alias for the defined name.
 // Alias panics if both names are already defined or if both are undefined.
 //
 // For example, if a flag named "v" is already defined using package flag,
 // then it is available as -v (or --v). Calling Alias("v", "verbose") makes the same
 // flag also available as --verbose.
 func Alias(short, long string) {
 	CommandLine.Alias(short, long)
 }
 
 // Alias introduces an alias for an existing flag name.
 // The short name must be a single letter, and the long name must be multiple letters.
 // Exactly one name must be defined as a flag already: the undefined name is introduced
 // as an alias for the defined name.
 // Alias panics if both names are already defined or if both are undefined.
 //
 // For example, if a flag named "v" is already defined using package flag,
 // then it is available as -v (or --v). Calling Alias("v", "verbose") makes the same
 // flag also available as --verbose.
 func (f *FlagSet) Alias(short, long string) {
 	f.init()
 	if short == "" || long == "" {
 		panic("Alias: invalid empty flag name")
 	}
 	if utf8.RuneCountInString(short) != 1 {
 		panic("Alias: invalid short flag name -" + short)
 	}
 	if utf8.RuneCountInString(long) == 1 {
 		panic("Alias: invalid long flag name --" + long)
 	}
 
 	f1 := f.Lookup(short)
 	f2 := f.Lookup(long)
 	if f1 == nil && f2 == nil {
 		panic("Alias: neither -" + short + " nor -" + long + " is a defined flag")
 	}
 	if f1 != nil && f2 != nil {
 		panic("Alias: both -" + short + " and -" + long + " are defined flags")
 	}
 
 	if f1 != nil {
 		f.alias[long] = short
 		f.unalias[short] = long
 	} else {
 		f.alias[short] = long
 		f.unalias[long] = short
 	}
 }
 
 // Aliases introduces zero or more aliases. The argument list must consist of an
 // even number of strings making up a sequence of short, long pairs to be passed
 // to Alias.
 func Aliases(list ...string) {
 	CommandLine.Aliases(list...)
 }
 
 // Aliases introduces zero or more aliases. The argument list must consist of an
 // even number of strings making up a sequence of short, long pairs to be passed
 // to Alias.
 func (f *FlagSet) Aliases(list ...string) {
 	if len(list)%2 != 0 {
 		panic("getopt: Aliases not invoked with pairs")
 	}
 	for i := 0; i < len(list); i += 2 {
 		f.Alias(list[i], list[i+1])
 	}
 }
 
 type boolFlag interface {
 	IsBoolFlag() bool
 }
 
 func (f *FlagSet) failf(format string, args ...interface{}) error {
 	err := fmt.Errorf(format, args...)
 	fmt.Fprintln(f.out(), err)
 	f.Usage()
 	return err
 }
 
 // defaultUsage is the default function to print a usage message.
 func (f *FlagSet) defaultUsage() {
 	if f.name == "" {
 		fmt.Fprintf(f.out(), "Usage:\n")
 	} else {
 		fmt.Fprintf(f.out(), "Usage of %s:\n", f.name)
 	}
 	f.PrintDefaults()
 }
 
 // Parse parses the command-line flags from os.Args[1:].
 func Parse() {
 	CommandLine.Parse(os.Args[1:])
 }
 
 // Parse parses flag definitions from the argument list,
 // which should not include the command name.
 // Parse must be called after all flags and aliases in the FlagSet are defined
 // and before flags are accessed by the program.
 // The return value will be flag.ErrHelp if -h or --help were used but not defined.
 func (f *FlagSet) Parse(args []string) error {
 	for len(args) > 0 {
 		arg := args[0]
 		if len(arg) < 2 || arg[0] != '-' {
 			break
 		}
 		args = args[1:]
 		if arg[:2] == "--" {
 			// Process single long option.
 			if arg == "--" {
 				break
 			}
 			name := arg[2:]
 			value := ""
 			haveValue := false
 			if i := strings.Index(name, "="); i >= 0 {
 				name, value = name[:i], name[i+1:]
 				haveValue = true
 			}
 			fg := f.Lookup(name)
 			if fg == nil {
 				if name == "h" || name == "help" {
 					// TODO ErrHelp
 				}
 				return f.failf("flag provided but not defined: --%s", name)
 			}
 			if b, ok := fg.Value.(boolFlag); ok && b.IsBoolFlag() {
 				if haveValue {
 					if err := fg.Value.Set(value); err != nil {
 						return f.failf("invalid boolean value %q for --%s: %v", value, name, err)
 					}
 				} else {
 					if err := fg.Value.Set("true"); err != nil {
 						return f.failf("invalid boolean flag %s: %v", name, err)
 					}
 				}
 				continue
 			}
 			if !haveValue {
 				if len(args) == 0 {
 					return f.failf("missing argument for --%s", name)
 				}
 				value, args = args[0], args[1:]
 			}
 			if err := fg.Value.Set(value); err != nil {
 				return f.failf("invalid value %q for flag --%s: %v", value, name, err)
 			}
 			continue
 		}
 
 		// Process one or more short options.
 		for arg = arg[1:]; arg != ""; {
 			r, size := utf8.DecodeRuneInString(arg)
 			if r == utf8.RuneError && size == 1 {
 				return f.failf("invalid UTF8 in command-line flags")
 			}
 			name := arg[:size]
 			arg = arg[size:]
 			fg := f.Lookup(name)
 			if fg == nil {
 				if name == "h" {
 					// TODO ErrHelp
 				}
 				return f.failf("flag provided but not defined: -%s", name)
 			}
 			if b, ok := fg.Value.(boolFlag); ok && b.IsBoolFlag() {
 				if err := fg.Value.Set("true"); err != nil {
 					return f.failf("invalid boolean flag %s: %v", name, err)
 				}
 				continue
 			}
 			if arg == "" {
 				if len(args) == 0 {
 					return f.failf("missing argument for -%s", name)
 				}
 				arg, args = args[0], args[1:]
 			}
 			if err := fg.Value.Set(arg); err != nil {
 				return f.failf("invalid value %q for flag -%s: %v", arg, name, err)
 			}
 			break // consumed arg
 		}
 	}
 
 	// Arrange for flag.NArg, flag.Args, etc to work properly.
 	f.FlagSet.Parse(append([]string{"--"}, args...))
 	return nil
 }
 
 // PrintDefaults is like flag.PrintDefaults but includes information
 // about short/long alias pairs and prints the correct syntax for
 // long flags.
 func PrintDefaults() {
 	CommandLine.PrintDefaults()
 }
 
 // PrintDefaults is like flag.PrintDefaults but includes information
 // about short/long alias pairs and prints the correct syntax for
 // long flags.
 func (f *FlagSet) PrintDefaults() {
 	f.FlagSet.VisitAll(func(fg *flag.Flag) {
 		name := fg.Name
 		short, long := "", ""
 		other := f.unalias[name]
 		if utf8.RuneCountInString(name) > 1 {
 			long, short = name, other
 		} else {
 			short, long = name, other
 		}
 		var s string
 		if short != "" {
 			s = fmt.Sprintf("  -%s", short) // Two spaces before -; see next two comments.
 			if long != "" {
 				s += ", --" + long
 			}
 		} else {
 			s = fmt.Sprintf("  --%s", long) // Two spaces before -; see next two comments.
 		}
 		name, usage := flag.UnquoteUsage(fg)
 		if len(name) > 0 {
 			s += " " + name
 		}
 
 		// Boolean flags of one ASCII letter are so common we
 		// treat them specially, putting their usage on the same line.
 		if len(s) <= 4 { // space, space, '-', 'x'.
 			s += "\t"
 		} else {
 			// Four spaces before the tab triggers good alignment
 			// for both 4- and 8-space tab stops.
 			s += "\n    \t"
 		}
 		s += usage
 		if !isZeroValue(fg, fg.DefValue) {
 			if strings.HasSuffix(reflect.TypeOf(fg.Value).String(), "stringValue") {
 				// put quotes on the value
 				s += fmt.Sprintf(" (default %q)", fg.DefValue)
 			} else {
 				s += fmt.Sprintf(" (default %v)", fg.DefValue)
 			}
 		}
 		fmt.Fprint(f.out(), s, "\n")
 	})
 }
 
 // isZeroValue guesses whether the string represents the zero
 // value for a flag. It is not accurate but in practice works OK.
 func isZeroValue(f *flag.Flag, value string) bool {
 	// Build a zero value of the flag's Value type, and see if the
 	// result of calling its String method equals the value passed in.
 	// This works unless the Value type is itself an interface type.
 	typ := reflect.TypeOf(f.Value)
 	var z reflect.Value
 	if typ.Kind() == reflect.Ptr {
 		z = reflect.New(typ.Elem())
 	} else {
 		z = reflect.Zero(typ)
 	}
 	if value == z.Interface().(flag.Value).String() {
 		return true
 	}
 
 	switch value {
 	case "false":
 		return true
 	case "":
 		return true
 	case "0":
 		return true
 	}
 	return false
 }