Add support for configuration subsets

.travis.yml

@@ -5,6 +5,11 @@ go:
   - 1.4
   - 1.3
 
-install:
+before_install:
   - go get github.com/tools/godep
+
+install:
   - godep restore
+
+script:
+  - go test -v ./...

README.md

@@ -108,6 +108,7 @@ GetStringMapString(key string) : map[string]string
 GetStringSlice(key string) : []string
 GetTime(key string) : time.Time
 IsSet(key string) : bool
+NewConfigSubset(prefix string) : *confer.Config
 ```
 
 ### Deep Configuration Data
@@ -120,6 +121,47 @@ Because periods aren't valid environment variable characters, when using automat
 LOGGER_STDOUT=/var/log/myapp go run server.go
 ```
 
+### Configuration Subsets
+An alternative to the `GetStringMap` / *Materialized paths* is a configuration subset. This allows you to create a new *confer.Config object which is a subset of the full configuration, specified by a key `prefix`. This makes passing around a subset of the configuration easy, allowing you to access the values using the getter methods listed above as you would normally. The setter methods are also supported on a configuration subset, as well as nested configuration subsets.
+
+##### Example Config
+```yml
+---
+my-app:
+    logging:
+        enabled: true
+        level: debug
+    server:
+        workers:
+            - 127.0.0.1
+            - 127.0.0.2
+            - 127.0.0.3
+    database:
+        bird:
+            host:     feathers
+            user:     postgres
+            password: superl33+
+        wind:
+            host:     sea-spray
+            user:     postgres
+            password: easyPZ
+```
+
+##### Config Subset
+
+```go
+windDbConfig := config.NewConfigSubset("my-app.database.wind")
+host := windDbConfig.GetString("host")
+```
+
+##### Nested Config Subset
+
+```go
+dbConfig := config.NewConfigSubset("my-app.database")
+windDbConfig := dbConfig.NewConfigSubset("wind")
+host := windDbConfig.GetString("host")
+```
+
 ### Environment Bindings
 
 

confer.go

@@ -45,6 +45,9 @@ type Config struct {
 
 	// The root path for configuration files.
 	rootPath string
+
+	// Key prefix for config subsets. The prefixes defines the root of the subset.
+	keyPrefix string
 }
 
 func NewConfig() *Config {
@@ -53,6 +56,7 @@ func NewConfig() *Config {
 	manager.attributes = NewConfigSource()
 	manager.env = NewEnvSource()
 	manager.rootPath = ""
+	manager.keyPrefix = ""
 
 	return manager
 }
@@ -152,6 +156,8 @@ func (manager *Config) BindEnv(input ...string) (err error) {
 // Get returns an interface..
 // Must be typecast or used by something that will typecast
 func (manager *Config) Get(key string) interface{} {
+	key = manager.GetFullKey(key)
+
 	jww.TRACE.Println("Looking for", key)
 
 	v := manager.Find(key)
@@ -178,6 +184,19 @@ func (manager *Config) Get(key string) interface{} {
 	return v
 }
 
+// NewConfigSubset returns a new config based on
+func (manager *Config) NewConfigSubset(prefix string) *Config {
+	configSubset := &Config{}
+	*configSubset = *manager
+
+	// Use GetFullKey here, as the config may already be a subset. This allows
+	// support of nested config subsets.
+	prefix = manager.GetFullKey(prefix)
+	configSubset.keyPrefix = prefix
+
+	return configSubset
+}
+
 // Returns true if the config key exists and is non-nil.
 func (manager *Config) IsSet(key string) bool {
 	t := manager.Get(key)
@@ -194,13 +213,15 @@ func (manager *Config) AutomaticEnv() {
 
 // Returns true if the key provided exists in our configuration.
 func (manager *Config) InConfig(key string) bool {
+	key = manager.GetFullKey(key)
 	_, exists := manager.attributes.Get(key)
 	return exists
 }
 
 // Set the default value for this key.
 // Default only used when no value is provided by the user via flag, config or ENV.
 func (manager *Config) SetDefault(key string, value interface{}) {
+	key = manager.GetFullKey(key)
 	if !manager.IsSet(key) {
 		manager.attributes.Set(key, value)
 	}
@@ -209,6 +230,7 @@ func (manager *Config) SetDefault(key string, value interface{}) {
 // Explicitly sets a value. Will not override command line arguments or
 // environment variables, as those sources have higher precedence.
 func (manager *Config) Set(key string, value interface{}) {
+	key = manager.GetFullKey(key)
 	manager.attributes.Set(key, value)
 }
 
@@ -288,6 +310,10 @@ func (manager *Config) AllKeys() []string {
 	leaves := map[string]struct{}{}
 	for _, key := range keys {
 
+		if manager.keyPrefix != "" && !strings.HasPrefix(key, manager.keyPrefix) {
+			continue
+		}
+
 		// Filter out leaves. This is really ineffecient.
 		val := manager.Get(key)
 		if val == nil {
@@ -323,3 +349,14 @@ func (manager *Config) Debug() {
 	fmt.Println("Config file attributes:")
 	pretty.Println(manager.attributes)
 }
+
+// GetFullKey accounts for a key prefix (config subset) and returns the full key.
+func (manager *Config) GetFullKey(key string) string {
+	if manager.keyPrefix != "" {
+		jww.TRACE.Println(key, "Using key prefix in operation: ", manager.keyPrefix)
+
+		key = manager.keyPrefix + "." + key
+	}
+
+	return key
+}

confer_test.go

@@ -366,6 +366,55 @@ func TestSpec(t *testing.T) {
 			})
 		})
 
+		Convey("Config Subset", func() {
+			config.ReadPaths("test/fixtures/application.yaml")
+			keyPrefix := "app.database"
+			configSubset := config.NewConfigSubset(keyPrefix)
+
+			Convey("Returning a config", func() {
+				So(configSubset, ShouldHaveSameTypeAs, NewConfig())
+			})
+
+			Convey("Subset gets", func() {
+				So(configSubset.GetString("host"), ShouldEqual, "localhost")
+				So(configSubset.GetString("user"), ShouldEqual, "postgres")
+				So(configSubset.InConfig("password"), ShouldEqual, true)
+			})
+
+			Convey("Subset sets", func() {
+				configSubset.SetDefault("port", 5432)
+				configSubset.Set("ssl.mode", "disable")
+				configSubset.Set("max_open_conns", 30)
+
+				So(configSubset.Get("ssl.mode"), ShouldEqual, "disable")
+				So(configSubset.Get("max_open_conns"), ShouldEqual, 30)
+				So(configSubset.IsSet("port"), ShouldEqual, true)
+				So(configSubset.Get("port"), ShouldEqual, 5432)
+
+				// Keys for config subset should be (8 in total): [
+				//	app.database app.database.host app.database.user app.database.password
+				//	app.database.port app.database.ssl app.database.ssl.mode
+				//	app.database.max_open_conns
+				// ]
+				So(len(configSubset.AllKeys()), ShouldEqual, 8)
+			})
+
+			Convey("Nested Subsets", func() {
+				configSubset.Set("ssl.mode", "verify-full")
+				configSubsetNested := configSubset.NewConfigSubset("ssl")
+				configSubsetNested.SetDefault("connect_timeout", 0)
+
+				So(configSubsetNested.IsSet("mode"), ShouldEqual, true)
+				So(configSubsetNested.GetString("mode"), ShouldEqual, "verify-full")
+				So(configSubsetNested.InConfig("connect_timeout"), ShouldEqual, true)
+
+				// Keys for nested config subset should be (3 in total): [
+				//	app.database.ssl app.database.ssl.mode app.database.ssl.connect_timeout
+				// ]
+				So(len(configSubsetNested.AllKeys()), ShouldEqual, 3)
+			})
+		})
+
 		Convey("Helpers", func() {
 			Convey("Returning an integer", func() {
 				config.Set("port", func() interface{} {