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|
package arg
import (
"encoding"
"fmt"
"io"
"os"
"reflect"
"strings"
)
// the width of the left column
const colWidth = 25
// Fail prints usage information to stderr and exits with non-zero status
func (p *Parser) Fail(msg string) {
p.WriteUsage(os.Stderr)
fmt.Fprintln(os.Stderr, "error:", msg)
os.Exit(-1)
}
// WriteUsage writes usage information to the given writer
func (p *Parser) WriteUsage(w io.Writer) {
var positionals, options []*spec
for _, spec := range p.specs {
if spec.positional {
positionals = append(positionals, spec)
} else {
options = append(options, spec)
}
}
if p.version != "" {
fmt.Fprintln(w, p.version)
}
fmt.Fprintf(w, "Usage: %s", p.config.Program)
// write the option component of the usage message
for _, spec := range options {
// prefix with a space
fmt.Fprint(w, " ")
if !spec.required {
fmt.Fprint(w, "[")
}
fmt.Fprint(w, synopsis(spec, "--"+spec.long))
if !spec.required {
fmt.Fprint(w, "]")
}
}
// write the positional component of the usage message
for _, spec := range positionals {
// prefix with a space
fmt.Fprint(w, " ")
up := strings.ToUpper(spec.long)
if spec.multiple {
if !spec.required {
fmt.Fprint(w, "[")
}
fmt.Fprintf(w, "%s [%s ...]", up, up)
if !spec.required {
fmt.Fprint(w, "]")
}
} else {
fmt.Fprint(w, up)
}
}
fmt.Fprint(w, "\n")
}
// WriteHelp writes the usage string followed by the full help string for each option
func (p *Parser) WriteHelp(w io.Writer) {
var positionals, options []*spec
for _, spec := range p.specs {
if spec.positional {
positionals = append(positionals, spec)
} else {
options = append(options, spec)
}
}
if p.description != "" {
fmt.Fprintln(w, p.description)
}
p.WriteUsage(w)
// write the list of positionals
if len(positionals) > 0 {
fmt.Fprint(w, "\nPositional arguments:\n")
for _, spec := range positionals {
left := " " + strings.ToUpper(spec.long)
fmt.Fprint(w, left)
if spec.help != "" {
if len(left)+2 < colWidth {
fmt.Fprint(w, strings.Repeat(" ", colWidth-len(left)))
} else {
fmt.Fprint(w, "\n"+strings.Repeat(" ", colWidth))
}
fmt.Fprint(w, spec.help)
}
fmt.Fprint(w, "\n")
}
}
// write the list of options
fmt.Fprint(w, "\nOptions:\n")
for _, spec := range options {
printOption(w, spec)
}
// write the list of built in options
printOption(w, &spec{boolean: true, long: "help", short: "h", help: "display this help and exit"})
if p.version != "" {
printOption(w, &spec{boolean: true, long: "version", help: "display version and exit"})
}
}
func printOption(w io.Writer, spec *spec) {
left := " " + synopsis(spec, "--"+spec.long)
if spec.short != "" {
left += ", " + synopsis(spec, "-"+spec.short)
}
fmt.Fprint(w, left)
if spec.help != "" {
if len(left)+2 < colWidth {
fmt.Fprint(w, strings.Repeat(" ", colWidth-len(left)))
} else {
fmt.Fprint(w, "\n"+strings.Repeat(" ", colWidth))
}
fmt.Fprint(w, spec.help)
}
// If spec.dest is not the zero value then a default value has been added.
v := spec.dest
if v.IsValid() {
z := reflect.Zero(v.Type())
if (v.Type().Comparable() && z.Type().Comparable() && v.Interface() != z.Interface()) || v.Kind() == reflect.Slice && !v.IsNil() {
if scalar, ok := v.Interface().(encoding.TextMarshaler); ok {
if value, err := scalar.MarshalText(); err != nil {
fmt.Fprintf(w, " [default: error: %v]", err)
} else {
fmt.Fprintf(w, " [default: %v]", string(value))
}
} else {
fmt.Fprintf(w, " [default: %v]", v)
}
}
}
fmt.Fprint(w, "\n")
}
func synopsis(spec *spec, form string) string {
if spec.boolean {
return form
}
return form + " " + strings.ToUpper(spec.long)
}
|
