README
¶
ViperVar
Variable resolution for Viper configurations
Install
go get -u github.com/wranders/vipervar
The What and Why
ViperVar allows you to resolve variables referencing other Viper settings within your configuration files. The cuts down on the number of lines that need to be editied if different settings contain similar information.
ViperVar has been tested against JSON, TOML, and YAML files. Any loaded configuration should work, but other formats are untested.
Resolving variables replaces the values within Viper, so this should be considered destructive. Unless a key is excluded, variables will be overwritten if Viper was used to save a configuration to file. If Viper is not used to write configuration files, then variables will remain intact within the file.
Your configuration file:
app_dir: "/home/user/app"
application:
name: "MyApp"
server:
root_url: "%SERVER.PROTOCOL%://%SERVER.DOMAIN%:%SERVER.PORT%/"
addr: "%SERVER.LISTEN%:%SERVER.PORT%"
domain: "myapp.foo"
protocol: "http"
listen: "0.0.0.0"
port: 80
database:
file: "%APP_DIR%/db/app.db"
. . .
Once resolved, becomes:
app_dir: "/home/user/app"
application:
name: "MyApp"
server:
root_url: "http://myapp.foo:80/"
addr: "0.0.0.0:80"
domain: "myapp.foo"
protocol: "http"
listen: "0.0.0.0"
port: 80
database:
file: "/home/user/app/db/app.db"
. . .
By default variable delimiters are the percent (%) sign, but are completely customizable with the exception of periods (.), since Viper uses those to delimit child keys, and slashes (/ and \), since distiguishing variables from paths would then be too difficult.
Getting Started
The default Viper can be used by simply using:
r := vipervar.NewResolver()
err := r.Resolve()
if err != nil {
panic(fmt.Errorf("Error resolving configuration:\n%s\n", err))
}
Or, a custom Viper can be resolved using NewResolverFrom(*viper.Viper):
v := viper.New()
err := v.ReadInConfig()
if err != nil {
panic(fmt.Errorf("Error reading config file: %s\n", err))
}
r := vipervar.NewResolverFrom(v)
err = r.Resolve()
if err != nil {
panic(fmt.Errorf("Error resolving configuration:\n%s\n", err))
}
Delimiters can be set using the SetDelimiters(start, end) function:
r := vipervar.NewResolver()
r.SetDelimiters(`{{`, `}}`)
Delimiters should be set using string literals. Under the hood, ViperVar uses regular expressions and all special characters are automatically escaped. Since slashes are considered illegal characters (reason above), escaping them would cause this action to fail and return an error.
All variables must reference an existing Viper setting. If an undefined setting key is encountered, Resolve will return an error containing all invalid keys and no changes will be made to the loaded Viper configuration.
Key Exclusion
If you have a setting that you do not want to be resolved, add it to the Resolver's ExcludedKeys slice:
r := vipervar.NewResolver()
r.ExcludedKeys = []string{"some_setting"}
r.ExcludedKeys = append(r.ExcludedKeys, "another_setting")
Watching
To re-resolve variables in a watched configuration file, add the Resolve function to your Viper's OnConfigChange function:
r := vipervar.NewResolver()
viper.WatchConfig()
viper.OnConfigChange(func(e fsnotify.Event) {
r.Resolve()
})
Documentation
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Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Resolver ¶
type Resolver struct {
ExcludeKeys []string
// contains filtered or unexported fields
}
Resolver contains the settings used to resolve variables in a Viper configuration
func NewResolverFrom ¶
NewResolverFrom uses the specified Viper configuration
Source Files