/
usage.go
193 lines (168 loc) · 4.4 KB
/
usage.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
package arg
import (
"fmt"
"io"
"os"
"strings"
)
// the width of the left column
const colWidth = 25
// to allow monkey patching in tests
var stderr = os.Stderr
// Fail prints usage information to stderr and exits with non-zero status
func (p *Parser) Fail(msg string) {
p.failWithCommand(msg, p.cmd)
}
// failWithCommand prints usage information for the given subcommand to stderr and exits with non-zero status
func (p *Parser) failWithCommand(msg string, cmd *command) {
p.writeUsageForCommand(stderr, cmd)
fmt.Fprintln(stderr, "error:", msg)
osExit(-1)
}
// WriteUsage writes usage information to the given writer
func (p *Parser) WriteUsage(w io.Writer) {
p.writeUsageForCommand(w, p.cmd)
}
// writeUsageForCommand writes usage information for the given subcommand
func (p *Parser) writeUsageForCommand(w io.Writer, cmd *command) {
var positionals, options []*spec
for _, spec := range cmd.specs {
if spec.positional {
positionals = append(positionals, spec)
} else {
options = append(options, spec)
}
}
if p.version != "" {
fmt.Fprintln(w, p.version)
}
// make a list of ancestor commands so that we print with full context
var ancestors []string
ancestor := cmd
for ancestor != nil {
ancestors = append(ancestors, ancestor.name)
ancestor = ancestor.parent
}
// print the beginning of the usage string
fmt.Fprint(w, "Usage:")
for i := len(ancestors) - 1; i >= 0; i-- {
fmt.Fprint(w, " "+ancestors[i])
}
// 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, " ")
if spec.multiple {
if !spec.required {
fmt.Fprint(w, "[")
}
fmt.Fprintf(w, "%s [%s ...]", spec.placeholder, spec.placeholder)
if !spec.required {
fmt.Fprint(w, "]")
}
} else {
fmt.Fprint(w, spec.placeholder)
}
}
// if the program supports subcommands, give a hint to the user about their existence
if len(cmd.subcommands) > 0 {
fmt.Fprint(w, " <command> [<args>]")
}
fmt.Fprint(w, "\n")
}
func printTwoCols(w io.Writer, left, help string, defaultVal string) {
lhs := " " + left
fmt.Fprint(w, lhs)
if help != "" {
if len(lhs)+2 < colWidth {
fmt.Fprint(w, strings.Repeat(" ", colWidth-len(lhs)))
} else {
fmt.Fprint(w, "\n"+strings.Repeat(" ", colWidth))
}
fmt.Fprint(w, help)
}
if defaultVal != "" {
fmt.Fprintf(w, " [default: %s]", defaultVal)
}
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) {
p.writeHelpForCommand(w, p.cmd)
}
// writeHelp writes the usage string for the given subcommand
func (p *Parser) writeHelpForCommand(w io.Writer, cmd *command) {
var positionals, options []*spec
for _, spec := range cmd.specs {
if spec.positional {
positionals = append(positionals, spec)
} else {
options = append(options, spec)
}
}
if p.description != "" {
fmt.Fprintln(w, p.description)
}
p.writeUsageForCommand(w, cmd)
// write the list of positionals
if len(positionals) > 0 {
fmt.Fprint(w, "\nPositional arguments:\n")
for _, spec := range positionals {
printTwoCols(w, spec.placeholder, spec.help, "")
}
}
// write the list of options
fmt.Fprint(w, "\nOptions:\n")
for _, spec := range options {
p.printOption(w, spec)
}
// write the list of built in options
p.printOption(w, &spec{
boolean: true,
long: "help",
short: "h",
help: "display this help and exit",
})
if p.version != "" {
p.printOption(w, &spec{
boolean: true,
long: "version",
help: "display version and exit",
})
}
// write the list of subcommands
if len(cmd.subcommands) > 0 {
fmt.Fprint(w, "\nCommands:\n")
for _, subcmd := range cmd.subcommands {
printTwoCols(w, subcmd.name, subcmd.help, "")
}
}
}
func (p *Parser) printOption(w io.Writer, spec *spec) {
left := synopsis(spec, "--"+spec.long)
if spec.short != "" {
left += ", " + synopsis(spec, "-"+spec.short)
}
printTwoCols(w, left, spec.help, spec.defaultVal)
}
func synopsis(spec *spec, form string) string {
if spec.boolean {
return form
}
return form + " " + spec.placeholder
}
func ptrTo(s string) *string {
return &s
}