| 1 | // Package opt implements command-line flag parsing.
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| 2 | package opt // import "modernc.org/opt"
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| 3 |
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| 4 | import (
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| 5 | "fmt"
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| 6 | "strings"
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| 7 | )
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| 8 |
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| 9 | type opt struct {
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| 10 | handler func(opt, arg string) error
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| 11 | name string
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| 12 |
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| 13 | arg bool // Enable argument, e.g. `-I foo` or `-I=foo`
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| 14 | }
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| 15 |
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| 16 | // A Set represents a set of defined options.
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| 17 | type Set struct {
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| 18 | cfg map[string]*opt
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| 19 | imm []*opt
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| 20 | }
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| 21 |
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| 22 | // NewSet returns a new, empty option set.
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| 23 | func NewSet() *Set { return &Set{cfg: map[string]*opt{}} }
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| 24 |
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| 25 | // Opt defines a simple option, e.g. `-f`. When the option is found during
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| 26 | // Parse, the handler is called with the value of the option, e.g. "-f".
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| 27 | func (p *Set) Opt(name string, handler func(opt string) error) {
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| 28 | p.cfg[name] = &opt{
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| 29 | handler: func(opt, arg string) error { return handler(opt) },
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| 30 | }
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| 31 | }
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| 32 |
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| 33 | // Arg defines a simple option with an argument, e.g. `-I foo` or `-I=foo`.
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| 34 | // Setting imm argument enables additionally `-Ifoo`. When the option is found
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| 35 | // during Parse, the handler is called with the values of the option and the
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| 36 | // argument, e.g. "-I" and "foo" for all of the variants.
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| 37 | func (p *Set) Arg(name string, imm bool, handler func(opt, arg string) error) {
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| 38 | switch {
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| 39 | case imm:
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| 40 | p.imm = append(p.imm, &opt{
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| 41 | handler: handler,
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| 42 | name: name,
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| 43 | })
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| 44 | default:
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| 45 | p.cfg[name] = &opt{
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| 46 | arg: true,
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| 47 | handler: handler,
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| 48 | name: name,
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| 49 | }
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| 50 | }
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| 51 | }
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| 52 |
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| 53 | // Parse parses opts. Must be called after all options are defined. The handler
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| 54 | // is called for all items in opts that were not defined before using Opt or
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| 55 | // Arg.
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| 56 | //
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| 57 | // If any handler returns a non-nil error, Parse will stop. If the error is of
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| 58 | // type Skip, the error returned by Parse will contain all the unprocessed
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| 59 | // items of opts.
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| 60 | //
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| 61 | // The opts slice must not be modified by any handler while Parser is
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| 62 | // executing.
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| 63 | func (p *Set) Parse(opts []string, handler func(string) error) (err error) {
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| 64 | defer func() {
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| 65 | switch err.(type) {
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| 66 | case Skip:
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| 67 | err = Skip(opts)
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| 68 | }
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| 69 | }()
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| 70 |
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| 71 | for len(opts) != 0 {
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| 72 | opt := opts[0]
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| 73 | opt0 := opt
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| 74 | opts = opts[1:]
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| 75 | var arg string
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| 76 | out:
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| 77 | switch {
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| 78 | case strings.HasPrefix(opt, "-"):
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| 79 | name := opt[1:]
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| 80 | for _, cfg := range p.imm {
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| 81 | if strings.HasPrefix(name, cfg.name) {
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| 82 | switch {
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| 83 | case name == cfg.name:
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| 84 | if len(opts) == 0 {
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| 85 | return fmt.Errorf("missing argument of %s", opt)
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| 86 | }
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| 87 |
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| 88 | if err = cfg.handler(opt, opts[0]); err != nil {
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| 89 | return err
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| 90 | }
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| 91 |
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| 92 | opts = opts[1:]
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| 93 | default:
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| 94 | opt = opt[:len(cfg.name)+1]
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| 95 | val := strings.TrimPrefix(name[len(cfg.name):], "=")
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| 96 | if err = cfg.handler(opt, val); err != nil {
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| 97 | return err
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| 98 | }
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| 99 | }
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| 100 | break out
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| 101 | }
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| 102 | }
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| 103 |
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| 104 | if n := strings.IndexByte(opt, '='); n > 0 {
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| 105 | arg = opt[n+1:]
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| 106 | name = opt[1:n]
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| 107 | opt = opt[:n]
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| 108 | }
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| 109 | switch cfg := p.cfg[name]; {
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| 110 | case cfg == nil:
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| 111 | if err = handler(opt0); err != nil {
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| 112 | return err
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| 113 | }
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| 114 | default:
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| 115 | switch {
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| 116 | case cfg.arg:
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| 117 | switch {
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| 118 | case arg != "":
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| 119 | if err = cfg.handler(opt, arg); err != nil {
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| 120 | return err
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| 121 | }
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| 122 | default:
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| 123 | if len(opts) == 0 {
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| 124 | return fmt.Errorf("missing argument of %s", opt)
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| 125 | }
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| 126 |
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| 127 | if err = cfg.handler(opt, opts[0]); err != nil {
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| 128 | return err
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| 129 | }
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| 130 |
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| 131 | opts = opts[1:]
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| 132 | }
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| 133 | default:
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| 134 | if err = cfg.handler(opt, ""); err != nil {
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| 135 | return err
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| 136 | }
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| 137 | }
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| 138 | }
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| 139 | default:
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| 140 | if opt == "" {
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| 141 | break
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| 142 | }
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| 143 |
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| 144 | if err = handler(opt); err != nil {
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| 145 | return err
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| 146 | }
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| 147 | }
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| 148 | }
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| 149 | return nil
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| 150 | }
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| 151 |
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| 152 | // Skip is an error that contains all unprocessed items passed to Parse.
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| 153 | type Skip []string
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| 154 |
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| 155 | func (s Skip) Error() string { return fmt.Sprint([]string(s)) }
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