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