68 lines
1.4 KiB
Go
68 lines
1.4 KiB
Go
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// Package flagenv provides the ability to populate flags from
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// environment variables.
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package flagenv
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import (
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"flag"
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"fmt"
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"log"
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"os"
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"strings"
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)
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// Specify a prefix for environment variables.
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var Prefix = ""
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func contains(list []*flag.Flag, f *flag.Flag) bool {
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for _, i := range list {
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if i == f {
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return true
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}
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}
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return false
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}
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// ParseSet parses the given flagset. The specified prefix will be applied to
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// the environment variable names.
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func ParseSet(prefix string, set *flag.FlagSet) error {
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var explicit []*flag.Flag
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var all []*flag.Flag
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set.Visit(func(f *flag.Flag) {
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explicit = append(explicit, f)
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})
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var err error
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set.VisitAll(func(f *flag.Flag) {
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if err != nil {
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return
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}
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all = append(all, f)
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if !contains(explicit, f) {
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name := strings.Replace(f.Name, ".", "_", -1)
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name = strings.Replace(name, "-", "_", -1)
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if prefix != "" {
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name = prefix + name
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}
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name = strings.ToUpper(name)
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val := os.Getenv(name)
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if val != "" {
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if ferr := f.Value.Set(val); ferr != nil {
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err = fmt.Errorf("failed to set flag %q with value %q", f.Name, val)
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}
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}
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}
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})
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return err
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}
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// Parse will set each defined flag from its corresponding environment
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// variable . If dots or dash are presents in the flag name, they will be
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// converted to underscores.
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//
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// If Parse fails, a fatal error is issued.
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func Parse() {
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if err := ParseSet(Prefix, flag.CommandLine); err != nil {
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log.Fatalln(err)
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}
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}
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