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
|
package kingpin
import (
"encoding/json"
"fmt"
"os"
"regexp"
"strings"
)
var (
envarTransformRegexp = regexp.MustCompile(`[^a-zA-Z_]+`)
)
// A Resolver retrieves flag values from an external source, such as a configuration file or environment variables.
type Resolver interface {
// Resolve key in the given parse context.
//
// A nil slice should be returned if the key can not be resolved.
Resolve(key string, context *ParseContext) ([]string, error)
}
// ResolverFunc is a function that is also a Resolver.
type ResolverFunc func(key string, context *ParseContext) ([]string, error)
func (r ResolverFunc) Resolve(key string, context *ParseContext) ([]string, error) {
return r(key, context)
}
// A resolver that pulls values from the flag defaults. This resolver is always installed in the ParseContext.
func defaultsResolver() Resolver {
return ResolverFunc(func(key string, context *ParseContext) ([]string, error) {
for _, clause := range context.CombinedFlagsAndArgs() {
if clause.name == key {
return clause.defaultValues, nil
}
}
return nil, nil
})
}
func parseEnvar(envar, sep string) []string {
value, ok := os.LookupEnv(envar)
if !ok {
return nil
}
if sep == "" {
return []string{value}
}
return strings.Split(value, sep)
}
// Resolves a clause value from the envar configured on that clause, if any.
func envarResolver(sep string) Resolver {
return ResolverFunc(func(key string, context *ParseContext) ([]string, error) {
for _, clause := range context.CombinedFlagsAndArgs() {
if key == clause.name {
if clause.noEnvar || clause.envar == "" {
return nil, nil
}
return parseEnvar(clause.envar, sep), nil
}
}
return nil, nil
})
}
// MapResolver resolves values from a static map.
func MapResolver(values map[string][]string) Resolver {
return ResolverFunc(func(key string, context *ParseContext) ([]string, error) {
return values[key], nil
})
}
// JSONResolver returns a Resolver that retrieves values from a JSON source.
func JSONResolver(data []byte) (Resolver, error) {
values := map[string]interface{}{}
err := json.Unmarshal(data, &values)
if err != nil {
return nil, err
}
mapping := map[string][]string{}
for key, value := range values {
sub, err := jsonDecodeValue(value)
if err != nil {
return nil, err
}
mapping[key] = sub
}
return MapResolver(mapping), nil
}
func jsonDecodeValue(value interface{}) ([]string, error) {
switch v := value.(type) {
case []interface{}:
out := []string{}
for _, sv := range v {
next, err := jsonDecodeValue(sv)
if err != nil {
return nil, err
}
out = append(out, next...)
}
return out, nil
case string:
return []string{v}, nil
case float64:
return []string{fmt.Sprintf("%v", v)}, nil
case bool:
if v {
return []string{"true"}, nil
}
return []string{"false"}, nil
}
return nil, fmt.Errorf("unsupported JSON value %v (of type %T)", value, value)
}
// RenamingResolver creates a resolver for remapping names for a child resolver.
//
// This is useful if your configuration file uses a naming convention that does not map directly to
// flag names.
func RenamingResolver(resolver Resolver, rename func(string) string) Resolver {
return ResolverFunc(func(key string, context *ParseContext) ([]string, error) {
return resolver.Resolve(rename(key), context)
})
}
// PrefixedEnvarResolver resolves any flag/argument via environment variables.
//
// "prefix" is the common-prefix for the environment variables. "separator", is the character used to separate
// multiple values within a single envar (eg. ";")
//
// With a prefix of APP_, flags in the form --some-flag will be transformed to APP_SOME_FLAG.
func PrefixedEnvarResolver(prefix, separator string) Resolver {
return ResolverFunc(func(key string, context *ParseContext) ([]string, error) {
key = envarTransform(prefix + key)
return parseEnvar(key, separator), nil
})
}
// DontResolve returns a Resolver that will never return values for the given keys, even if provided.
func DontResolve(resolver Resolver, keys ...string) Resolver {
disabled := map[string]bool{}
for _, key := range keys {
disabled[key] = true
}
return ResolverFunc(func(key string, context *ParseContext) ([]string, error) {
if disabled[key] {
return nil, nil
}
return resolver.Resolve(key, context)
})
}
func envarTransform(name string) string {
return strings.ToUpper(envarTransformRegexp.ReplaceAllString(name, "_"))
}
|
