Fix nil pointer on watch function (#568)

It was exported in previous commit, but we have GetConfigFileUsed -- so use that.

.travis.yml

@@ -2,8 +2,9 @@ go_import_path: github.com/spf13/viper
 
 language: go
 go:
-  - 1.7.5
-  - 1.8
+  - 1.7.x
+  - 1.8.x
+  - 1.9.x
   - tip
 
 os:
@@ -17,6 +18,7 @@ matrix:
 
 script:
   - go install ./...
+  - diff -u <(echo -n) <(gofmt -d .)
   - go test -v ./...
 
 after_success:

README.md

@@ -6,18 +6,19 @@ Many Go projects are built using Viper including:
 
 * [Hugo](http://gohugo.io)
 * [EMC RexRay](http://rexray.readthedocs.org/en/stable/)
-* [Imgur's Incus](https://github.com/Imgur/incus)
+* [Imgur’s Incus](https://github.com/Imgur/incus)
 * [Nanobox](https://github.com/nanobox-io/nanobox)/[Nanopack](https://github.com/nanopack)
 * [Docker Notary](https://github.com/docker/Notary)
 * [BloomApi](https://www.bloomapi.com/)
 * [doctl](https://github.com/digitalocean/doctl)
+* [Clairctl](https://github.com/jgsqware/clairctl)
 
 [![Build Status](https://travis-ci.org/spf13/viper.svg)](https://travis-ci.org/spf13/viper) [![Join the chat at https://gitter.im/spf13/viper](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/spf13/viper?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![GoDoc](https://godoc.org/github.com/spf13/viper?status.svg)](https://godoc.org/github.com/spf13/viper)
 
 
 ## What is Viper?
 
-Viper is a complete configuration solution for go applications including 12 factor apps. It is designed
+Viper is a complete configuration solution for Go applications including 12-Factor apps. It is designed
 to work within an application, and can handle all types of configuration needs
 and formats. It supports:
 
@@ -68,7 +69,7 @@ Viper configuration keys are case insensitive.
 ### Establishing Defaults
 
 A good configuration system will support default values. A default value is not
-required for a key, but it's useful in the event that a key hasn’t been set via
+required for a key, but it’s useful in the event that a key hasn’t been set via
 config file, environment variable, remote configuration or flag.
 
 Examples:
@@ -116,10 +117,10 @@ Optionally you can provide a function for Viper to run each time a change occurs
 **Make sure you add all of the configPaths prior to calling `WatchConfig()`**
 
 ```go
-		viper.WatchConfig()
-		viper.OnConfigChange(func(e fsnotify.Event) {
-			fmt.Println("Config file changed:", e.Name)
-		})
+viper.WatchConfig()
+viper.OnConfigChange(func(e fsnotify.Event) {
+	fmt.Println("Config file changed:", e.Name)
+})
 ```
 
 ### Reading Config from io.Reader
@@ -184,7 +185,7 @@ with ENV:
  * `AutomaticEnv()`
  * `BindEnv(string...) : error`
  * `SetEnvPrefix(string)`
- * `SetEnvReplacer(string...) *strings.Replacer`
+ * `SetEnvKeyReplacer(string...) *strings.Replacer`
 
 _When working with ENV variables, it’s important to recognize that Viper
 treats ENV variables as case sensitive._
@@ -211,7 +212,7 @@ time a `viper.Get` request is made. It will apply the following rules. It will
 check for a environment variable with a name matching the key uppercased and
 prefixed with the `EnvPrefix` if set.
 
-`SetEnvReplacer` allows you to use a `strings.Replacer` object to rewrite Env
+`SetEnvKeyReplacer` allows you to use a `strings.Replacer` object to rewrite Env
 keys to an extent. This is useful if you want to use `-` or something in your
 `Get()` calls, but want your environmental variables to use `_` delimiters. An
 example of using it can be found in `viper_test.go`.
@@ -236,7 +237,7 @@ Like `BindEnv`, the value is not set when the binding method is called, but when
 it is accessed. This means you can bind as early as you want, even in an
 `init()` function.
 
-The `BindPFlag()` method provides this functionality.
+For individual flags, the `BindPFlag()` method provides this functionality.
 
 Example:
 
@@ -245,6 +246,19 @@ serverCmd.Flags().Int("port", 1138, "Port to run Application server on")
 viper.BindPFlag("port", serverCmd.Flags().Lookup("port"))
 ```
 
+You can also bind an existing set of pflags (pflag.FlagSet):
+
+Example:
+
+```go
+pflag.Int("flagname", 1234, "help message for flagname")
+
+pflag.Parse()
+viper.BindPFlags(pflag.CommandLine)
+
+i := viper.GetInt("flagname") // retrieve values from viper instead of pflag
+```
+
 The use of [pflag](https://github.com/spf13/pflag/) in Viper does not preclude
 the use of other packages that use the [flag](https://golang.org/pkg/flag/)
 package from the standard library. The pflag package can handle the flags
@@ -263,15 +277,23 @@ import (
 )
 
 func main() {
+
+	// using standard library "flag" package
+	flag.Int("flagname", 1234, "help message for flagname")
+
 	pflag.CommandLine.AddGoFlagSet(flag.CommandLine)
 	pflag.Parse()
-    ...
+	viper.BindPFlags(pflag.CommandLine)
+
+	i := viper.GetInt("flagname") // retrieve value from viper
+
+	...
 }
 ```
 
 #### Flag interfaces
 
-Viper provides two Go interfaces to bind other flag systems if you don't use `Pflags`.
+Viper provides two Go interfaces to bind other flag systems if you don’t use `Pflags`.
 
 `FlagValue` represents a single flag. This is a very simple example on how to implement this interface:
 
@@ -401,7 +423,7 @@ go func(){
 
 ## Getting Values From Viper
 
-In Viper, there are a few ways to get a value depending on the value's type.
+In Viper, there are a few ways to get a value depending on the value’s type.
 The following functions and methods exist:
 
  * `Get(key string) : interface{}`
@@ -531,7 +553,7 @@ func NewCache(cfg *Viper) *Cache {...}
 ```
 
 which creates a cache based on config information formatted as `subv`.
-Now it's easy to create these 2 caches separately as:
+Now it’s easy to create these 2 caches separately as:
 
 ```go
 cfg1 := viper.Sub("app.cache1")
@@ -575,13 +597,13 @@ initialization needed to begin using Viper. Since most applications will want
 to use a single central repository for their configuration, the viper package
 provides this. It is similar to a singleton.
 
-In all of the examples above, they demonstrate using viper in it's singleton
+In all of the examples above, they demonstrate using viper in its singleton
 style approach.
 
 ### Working with multiple vipers
 
 You can also create many different vipers for use in your application. Each will
-have it’s own unique set of configurations and values. Each can read from a
+have its own unique set of configurations and values. Each can read from a
 different config file, key value store, etc. All of the functions that viper
 package supports are mirrored as methods on a viper.
 

flags_test.go

@@ -62,5 +62,4 @@ func TestBindFlagValue(t *testing.T) {
 	flag.Changed = true //hack for pflag usage
 
 	assert.Equal(t, "testing_mutate", Get("testvalue"))
-
 }

nohup.out

@@ -1 +0,0 @@
-QProcess::start: Process is already running

remote/remote.go

@@ -8,10 +8,11 @@ package remote
 
 import (
 	"bytes"
-	"github.com/spf13/viper"
-	crypt "github.com/xordataexchange/crypt/config"
 	"io"
 	"os"
+
+	"github.com/spf13/viper"
+	crypt "github.com/xordataexchange/crypt/config"
 )
 
 type remoteConfigProvider struct{}
@@ -33,17 +34,45 @@ func (rc remoteConfigProvider) Watch(rp viper.RemoteProvider) (io.Reader, error)
 	if err != nil {
 		return nil, err
 	}
-	resp := <-cm.Watch(rp.Path(), nil)
-	err = resp.Error
+	resp, err := cm.Get(rp.Path())
 	if err != nil {
 		return nil, err
 	}
 
-	return bytes.NewReader(resp.Value), nil
+	return bytes.NewReader(resp), nil
+}
+
+func (rc remoteConfigProvider) WatchChannel(rp viper.RemoteProvider) (<-chan *viper.RemoteResponse, chan bool) {
+	cm, err := getConfigManager(rp)
+	if err != nil {
+		return nil, nil
+	}
+	quit := make(chan bool)
+	quitwc := make(chan bool)
+	viperResponsCh := make(chan *viper.RemoteResponse)
+	cryptoResponseCh := cm.Watch(rp.Path(), quit)
+	// need this function to convert the Channel response form crypt.Response to viper.Response
+	go func(cr <-chan *crypt.Response, vr chan<- *viper.RemoteResponse, quitwc <-chan bool, quit chan<- bool) {
+		for {
+			select {
+			case <-quitwc:
+				quit <- true
+				return
+			case resp := <-cr:
+				vr <- &viper.RemoteResponse{
+					Error: resp.Error,
+					Value: resp.Value,
+				}
+
+			}
+
+		}
+	}(cryptoResponseCh, viperResponsCh, quitwc, quit)
+
+	return viperResponsCh, quitwc
 }
 
 func getConfigManager(rp viper.RemoteProvider) (crypt.ConfigManager, error) {
-
 	var cm crypt.ConfigManager
 	var err error
 
@@ -69,7 +98,6 @@ func getConfigManager(rp viper.RemoteProvider) (crypt.ConfigManager, error) {
 		return nil, err
 	}
 	return cm, nil
-
 }
 
 func init() {

util.go

@@ -11,22 +11,16 @@
 package viper
 
 import (
-	"bytes"
-	"encoding/json"
 	"fmt"
-	"io"
 	"os"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"unicode"
 
-	"github.com/hashicorp/hcl"
-	"github.com/magiconair/properties"
-	toml "github.com/pelletier/go-toml"
+	"github.com/spf13/afero"
 	"github.com/spf13/cast"
 	jww "github.com/spf13/jwalterweatherman"
-	"gopkg.in/yaml.v2"
 )
 
 // ConfigParseError denotes failing to parse configuration file.
@@ -121,8 +115,8 @@ func absPathify(inPath string) string {
 }
 
 // Check if File / Directory Exists
-func exists(path string) (bool, error) {
-	_, err := v.fs.Stat(path)
+func exists(fs afero.Fs, path string) (bool, error) {
+	_, err := fs.Stat(path)
 	if err == nil {
 		return true, nil
 	}
@@ -152,61 +146,6 @@ func userHomeDir() string {
 	return os.Getenv("HOME")
 }
 
-func unmarshallConfigReader(in io.Reader, c map[string]interface{}, configType string) error {
-	buf := new(bytes.Buffer)
-	buf.ReadFrom(in)
-
-	switch strings.ToLower(configType) {
-	case "yaml", "yml":
-		if err := yaml.Unmarshal(buf.Bytes(), &c); err != nil {
-			return ConfigParseError{err}
-		}
-
-	case "json":
-		if err := json.Unmarshal(buf.Bytes(), &c); err != nil {
-			return ConfigParseError{err}
-		}
-
-	case "hcl":
-		obj, err := hcl.Parse(string(buf.Bytes()))
-		if err != nil {
-			return ConfigParseError{err}
-		}
-		if err = hcl.DecodeObject(&c, obj); err != nil {
-			return ConfigParseError{err}
-		}
-
-	case "toml":
-		tree, err := toml.LoadReader(buf)
-		if err != nil {
-			return ConfigParseError{err}
-		}
-		tmap := tree.ToMap()
-		for k, v := range tmap {
-			c[k] = v
-		}
-
-	case "properties", "props", "prop":
-		var p *properties.Properties
-		var err error
-		if p, err = properties.Load(buf.Bytes(), properties.UTF8); err != nil {
-			return ConfigParseError{err}
-		}
-		for _, key := range p.Keys() {
-			value, _ := p.Get(key)
-			// recursively build nested maps
-			path := strings.Split(key, ".")
-			lastKey := strings.ToLower(path[len(path)-1])
-			deepestMap := deepSearch(c, path[0:len(path)-1])
-			// set innermost value
-			deepestMap[lastKey] = value
-		}
-	}
-
-	insensitiviseMap(c)
-	return nil
-}
-
 func safeMul(a, b uint) uint {
 	c := a * b
 	if a > 1 && b > 1 && c/b != a {

util_test.go

@@ -16,7 +16,6 @@ import (
 )
 
 func TestCopyAndInsensitiviseMap(t *testing.T) {
-
 	var (
 		given = map[string]interface{}{
 			"Foo": 32,

viper.go

@@ -21,6 +21,8 @@ package viper
 
 import (
 	"bytes"
+	"encoding/csv"
+	"encoding/json"
 	"fmt"
 	"io"
 	"log"
@@ -30,16 +32,37 @@ import (
 	"strings"
 	"time"
 
+	yaml "gopkg.in/yaml.v2"
+
 	"github.com/fsnotify/fsnotify"
+	"github.com/hashicorp/hcl"
+	"github.com/hashicorp/hcl/hcl/printer"
+	"github.com/magiconair/properties"
 	"github.com/mitchellh/mapstructure"
+	toml "github.com/pelletier/go-toml"
 	"github.com/spf13/afero"
 	"github.com/spf13/cast"
 	jww "github.com/spf13/jwalterweatherman"
 	"github.com/spf13/pflag"
 )
 
+// ConfigMarshalError happens when failing to marshal the configuration.
+type ConfigMarshalError struct {
+	err error
+}
+
+// Error returns the formatted configuration error.
+func (e ConfigMarshalError) Error() string {
+	return fmt.Sprintf("While marshaling config: %s", e.err.Error())
+}
+
 var v *Viper
 
+type RemoteResponse struct {
+	Value []byte
+	Error error
+}
+
 func init() {
 	v = New()
 }
@@ -47,6 +70,7 @@ func init() {
 type remoteConfigFactory interface {
 	Get(rp RemoteProvider) (io.Reader, error)
 	Watch(rp RemoteProvider) (io.Reader, error)
+	WatchChannel(rp RemoteProvider) (<-chan *RemoteResponse, chan bool)
 }
 
 // RemoteConfig is optional, see the remote package
@@ -62,8 +86,7 @@ func (str UnsupportedConfigError) Error() string {
 }
 
 // UnsupportedRemoteProviderError denotes encountering an unsupported remote
-// provider. Currently only etcd and Consul are
-// supported.
+// provider. Currently only etcd and Consul are supported.
 type UnsupportedRemoteProviderError string
 
 // Error returns the formatted remote provider error.
@@ -156,6 +179,10 @@ type Viper struct {
 	aliases        map[string]string
 	typeByDefValue bool
 
+	// Store read properties on the object so that we can write back in order with comments.
+	// This will only be used if the configuration read is a properties file.
+	properties *properties.Properties
+
 	onConfigChange func(fsnotify.Event)
 }
 
@@ -182,7 +209,7 @@ func New() *Viper {
 // can use it in their testing as well.
 func Reset() {
 	v = New()
-	SupportedExts = []string{"json", "toml", "yaml", "yml", "hcl"}
+	SupportedExts = []string{"json", "toml", "yaml", "yml", "properties", "props", "prop", "hcl"}
 	SupportedRemoteProviders = []string{"etcd", "consul"}
 }
 
@@ -262,7 +289,9 @@ func (v *Viper) WatchConfig() {
 							if err != nil {
 								log.Println("error:", err)
 							}
-							v.onConfigChange(event)
+							if v.onConfigChange != nil {
+								v.onConfigChange(event)
+							}
 						}
 					}
 				case err := <-watcher.Errors:
@@ -276,8 +305,8 @@ func (v *Viper) WatchConfig() {
 	}()
 }
 
-// SetConfigFile explicitly defines the path, name and extension of the config file
-// Viper will use this and not check any of the config paths
+// SetConfigFile explicitly defines the path, name and extension of the config file.
+// Viper will use this and not check any of the config paths.
 func SetConfigFile(in string) { v.SetConfigFile(in) }
 func (v *Viper) SetConfigFile(in string) {
 	if in != "" {
@@ -286,8 +315,8 @@ func (v *Viper) SetConfigFile(in string) {
 }
 
 // SetEnvPrefix defines a prefix that ENVIRONMENT variables will use.
-// E.g. if your prefix is "spf", the env registry
-// will look for env. variables that start with "SPF_"
+// E.g. if your prefix is "spf", the env registry will look for env
+// variables that start with "SPF_".
 func SetEnvPrefix(in string) { v.SetEnvPrefix(in) }
 func (v *Viper) SetEnvPrefix(in string) {
 	if in != "" {
@@ -305,11 +334,11 @@ func (v *Viper) mergeWithEnvPrefix(in string) string {
 
 // TODO: should getEnv logic be moved into find(). Can generalize the use of
 // rewriting keys many things, Ex: Get('someKey') -> some_key
-// (cammel case to snake case for JSON keys perhaps)
+// (camel case to snake case for JSON keys perhaps)
 
 // getEnv is a wrapper around os.Getenv which replaces characters in the original
-// key. This allows env vars which have different keys then the config object
-// keys
+// key. This allows env vars which have different keys than the config object
+// keys.
 func (v *Viper) getEnv(key string) string {
 	if v.envKeyReplacer != nil {
 		key = v.envKeyReplacer.Replace(key)
@@ -317,7 +346,7 @@ func (v *Viper) getEnv(key string) string {
 	return os.Getenv(key)
 }
 
-// ConfigFileUsed returns the file used to populate the config registry
+// ConfigFileUsed returns the file used to populate the config registry.
 func ConfigFileUsed() string            { return v.ConfigFileUsed() }
 func (v *Viper) ConfigFileUsed() string { return v.configFile }
 
@@ -590,32 +619,33 @@ func (v *Viper) Get(key string) interface{} {
 		return nil
 	}
 
-	valType := val
 	if v.typeByDefValue {
 		// TODO(bep) this branch isn't covered by a single test.
+		valType := val
 		path := strings.Split(lcaseKey, v.keyDelim)
 		defVal := v.searchMap(v.defaults, path)
 		if defVal != nil {
 			valType = defVal
 		}
+
+		switch valType.(type) {
+		case bool:
+			return cast.ToBool(val)
+		case string:
+			return cast.ToString(val)
+		case int64, int32, int16, int8, int:
+			return cast.ToInt(val)
+		case float64, float32:
+			return cast.ToFloat64(val)
+		case time.Time:
+			return cast.ToTime(val)
+		case time.Duration:
+			return cast.ToDuration(val)
+		case []string:
+			return cast.ToStringSlice(val)
+		}
 	}
 
-	switch valType.(type) {
-	case bool:
-		return cast.ToBool(val)
-	case string:
-		return cast.ToString(val)
-	case int64, int32, int16, int8, int:
-		return cast.ToInt(val)
-	case float64, float32:
-		return cast.ToFloat64(val)
-	case time.Time:
-		return cast.ToTime(val)
-	case time.Duration:
-		return cast.ToDuration(val)
-	case []string:
-		return cast.ToStringSlice(val)
-	}
 	return val
 }
 
@@ -713,7 +743,15 @@ func (v *Viper) GetSizeInBytes(key string) uint {
 // UnmarshalKey takes a single key and unmarshals it into a Struct.
 func UnmarshalKey(key string, rawVal interface{}) error { return v.UnmarshalKey(key, rawVal) }
 func (v *Viper) UnmarshalKey(key string, rawVal interface{}) error {
-	return mapstructure.Decode(v.Get(key), rawVal)
+	err := decode(v.Get(key), defaultDecoderConfig(rawVal))
+
+	if err != nil {
+		return err
+	}
+
+	v.insensitiviseMaps()
+
+	return nil
 }
 
 // Unmarshal unmarshals the config into a Struct. Make sure that the tags
@@ -732,13 +770,16 @@ func (v *Viper) Unmarshal(rawVal interface{}) error {
 }
 
 // defaultDecoderConfig returns default mapsstructure.DecoderConfig with suppot
-// of time.Duration values
+// of time.Duration values & string slices
 func defaultDecoderConfig(output interface{}) *mapstructure.DecoderConfig {
 	return &mapstructure.DecoderConfig{
 		Metadata:         nil,
 		Result:           output,
 		WeaklyTypedInput: true,
-		DecodeHook:       mapstructure.StringToTimeDurationHookFunc(),
+		DecodeHook: mapstructure.ComposeDecodeHookFunc(
+			mapstructure.StringToTimeDurationHookFunc(),
+			mapstructure.StringToSliceHookFunc(","),
+		),
 	}
 }
 
@@ -799,7 +840,7 @@ func (v *Viper) BindFlagValues(flags FlagValueSet) (err error) {
 }
 
 // BindFlagValue binds a specific key to a FlagValue.
-// Example(where serverCmd is a Cobra instance):
+// Example (where serverCmd is a Cobra instance):
 //
 //	 serverCmd.Flags().Int("port", 1138, "Port to run Application server on")
 //	 Viper.BindFlagValue("port", serverCmd.Flags().Lookup("port"))
@@ -880,7 +921,9 @@ func (v *Viper) find(lcaseKey string) interface{} {
 			return cast.ToBool(flag.ValueString())
 		case "stringSlice":
 			s := strings.TrimPrefix(flag.ValueString(), "[")
-			return strings.TrimSuffix(s, "]")
+			s = strings.TrimSuffix(s, "]")
+			res, _ := readAsCSV(s)
+			return res
 		default:
 			return flag.ValueString()
 		}
@@ -947,7 +990,9 @@ func (v *Viper) find(lcaseKey string) interface{} {
 			return cast.ToBool(flag.ValueString())
 		case "stringSlice":
 			s := strings.TrimPrefix(flag.ValueString(), "[")
-			return strings.TrimSuffix(s, "]")
+			s = strings.TrimSuffix(s, "]")
+			res, _ := readAsCSV(s)
+			return res
 		default:
 			return flag.ValueString()
 		}
@@ -957,6 +1002,15 @@ func (v *Viper) find(lcaseKey string) interface{} {
 	return nil
 }
 
+func readAsCSV(val string) ([]string, error) {
+	if val == "" {
+		return []string{}, nil
+	}
+	stringReader := strings.NewReader(val)
+	csvReader := csv.NewReader(stringReader)
+	return csvReader.Read()
+}
+
 // IsSet checks to see if the key has been set in any of the data locations.
 // IsSet is case-insensitive for a key.
 func IsSet(key string) bool { return v.IsSet(key) }
@@ -1088,6 +1142,7 @@ func (v *Viper) ReadInConfig() error {
 		return UnsupportedConfigError(v.getConfigType())
 	}
 
+	jww.DEBUG.Println("Reading file: ", filename)
 	file, err := afero.ReadFile(v.fs, filename)
 	if err != nil {
 		return err
@@ -1147,6 +1202,195 @@ func (v *Viper) MergeConfig(in io.Reader) error {
 	return nil
 }
 
+// WriteConfig writes the current configuration to a file.
+func WriteConfig() error { return v.WriteConfig() }
+func (v *Viper) WriteConfig() error {
+	filename, err := v.getConfigFile()
+	if err != nil {
+		return err
+	}
+	return v.writeConfig(filename, true)
+}
+
+// SafeWriteConfig writes current configuration to file only if the file does not exist.
+func SafeWriteConfig() error { return v.SafeWriteConfig() }
+func (v *Viper) SafeWriteConfig() error {
+	filename, err := v.getConfigFile()
+	if err != nil {
+		return err
+	}
+	return v.writeConfig(filename, false)
+}
+
+// WriteConfigAs writes current configuration to a given filename.
+func WriteConfigAs(filename string) error { return v.WriteConfigAs(filename) }
+func (v *Viper) WriteConfigAs(filename string) error {
+	return v.writeConfig(filename, true)
+}
+
+// SafeWriteConfigAs writes current configuration to a given filename if it does not exist.
+func SafeWriteConfigAs(filename string) error { return v.SafeWriteConfigAs(filename) }
+func (v *Viper) SafeWriteConfigAs(filename string) error {
+	return v.writeConfig(filename, false)
+}
+
+func writeConfig(filename string, force bool) error { return v.writeConfig(filename, force) }
+func (v *Viper) writeConfig(filename string, force bool) error {
+	jww.INFO.Println("Attempting to write configuration to file.")
+	ext := filepath.Ext(filename)
+	if len(ext) <= 1 {
+		return fmt.Errorf("Filename: %s requires valid extension.", filename)
+	}
+	configType := ext[1:]
+	if !stringInSlice(configType, SupportedExts) {
+		return UnsupportedConfigError(configType)
+	}
+	if v.config == nil {
+		v.config = make(map[string]interface{})
+	}
+	var flags int
+	if force == true {
+		flags = os.O_CREATE | os.O_TRUNC | os.O_WRONLY
+	} else {
+		if _, err := os.Stat(filename); os.IsNotExist(err) {
+			flags = os.O_WRONLY
+		} else {
+			return fmt.Errorf("File: %s exists. Use WriteConfig to overwrite.", filename)
+		}
+	}
+	f, err := v.fs.OpenFile(filename, flags, os.FileMode(0644))
+	if err != nil {
+		return err
+	}
+	return v.marshalWriter(f, configType)
+}
+
+// Unmarshal a Reader into a map.
+// Should probably be an unexported function.
+func unmarshalReader(in io.Reader, c map[string]interface{}) error {
+	return v.unmarshalReader(in, c)
+}
+func (v *Viper) unmarshalReader(in io.Reader, c map[string]interface{}) error {
+	buf := new(bytes.Buffer)
+	buf.ReadFrom(in)
+
+	switch strings.ToLower(v.getConfigType()) {
+	case "yaml", "yml":
+		if err := yaml.Unmarshal(buf.Bytes(), &c); err != nil {
+			return ConfigParseError{err}
+		}
+
+	case "json":
+		if err := json.Unmarshal(buf.Bytes(), &c); err != nil {
+			return ConfigParseError{err}
+		}
+
+	case "hcl":
+		obj, err := hcl.Parse(string(buf.Bytes()))
+		if err != nil {
+			return ConfigParseError{err}
+		}
+		if err = hcl.DecodeObject(&c, obj); err != nil {
+			return ConfigParseError{err}
+		}
+
+	case "toml":
+		tree, err := toml.LoadReader(buf)
+		if err != nil {
+			return ConfigParseError{err}
+		}
+		tmap := tree.ToMap()
+		for k, v := range tmap {
+			c[k] = v
+		}
+
+	case "properties", "props", "prop":
+		v.properties = properties.NewProperties()
+		var err error
+		if v.properties, err = properties.Load(buf.Bytes(), properties.UTF8); err != nil {
+			return ConfigParseError{err}
+		}
+		for _, key := range v.properties.Keys() {
+			value, _ := v.properties.Get(key)
+			// recursively build nested maps
+			path := strings.Split(key, ".")
+			lastKey := strings.ToLower(path[len(path)-1])
+			deepestMap := deepSearch(c, path[0:len(path)-1])
+			// set innermost value
+			deepestMap[lastKey] = value
+		}
+	}
+
+	insensitiviseMap(c)
+	return nil
+}
+
+// Marshal a map into Writer.
+func marshalWriter(f afero.File, configType string) error {
+	return v.marshalWriter(f, configType)
+}
+func (v *Viper) marshalWriter(f afero.File, configType string) error {
+	c := v.AllSettings()
+	switch configType {
+	case "json":
+		b, err := json.MarshalIndent(c, "", "  ")
+		if err != nil {
+			return ConfigMarshalError{err}
+		}
+		_, err = f.WriteString(string(b))
+		if err != nil {
+			return ConfigMarshalError{err}
+		}
+
+	case "hcl":
+		b, err := json.Marshal(c)
+		ast, err := hcl.Parse(string(b))
+		if err != nil {
+			return ConfigMarshalError{err}
+		}
+		err = printer.Fprint(f, ast.Node)
+		if err != nil {
+			return ConfigMarshalError{err}
+		}
+
+	case "prop", "props", "properties":
+		if v.properties == nil {
+			v.properties = properties.NewProperties()
+		}
+		p := v.properties
+		for _, key := range v.AllKeys() {
+			_, _, err := p.Set(key, v.GetString(key))
+			if err != nil {
+				return ConfigMarshalError{err}
+			}
+		}
+		_, err := p.WriteComment(f, "#", properties.UTF8)
+		if err != nil {
+			return ConfigMarshalError{err}
+		}
+
+	case "toml":
+		t, err := toml.TreeFromMap(c)
+		if err != nil {
+			return ConfigMarshalError{err}
+		}
+		s := t.String()
+		if _, err := f.WriteString(s); err != nil {
+			return ConfigMarshalError{err}
+		}
+
+	case "yaml", "yml":
+		b, err := yaml.Marshal(c)
+		if err != nil {
+			return ConfigMarshalError{err}
+		}
+		if _, err = f.WriteString(string(b)); err != nil {
+			return ConfigMarshalError{err}
+		}
+	}
+	return nil
+}
+
 func keyExists(k string, m map[string]interface{}) string {
 	lk := strings.ToLower(k)
 	for mk := range m {
@@ -1255,14 +1499,8 @@ func (v *Viper) WatchRemoteConfig() error {
 	return v.watchKeyValueConfig()
 }
 
-// Unmarshall a Reader into a map.
-// Should probably be an unexported function.
-func unmarshalReader(in io.Reader, c map[string]interface{}) error {
-	return v.unmarshalReader(in, c)
-}
-
-func (v *Viper) unmarshalReader(in io.Reader, c map[string]interface{}) error {
-	return unmarshallConfigReader(in, c, v.getConfigType())
+func (v *Viper) WatchRemoteConfigOnChannel() error {
+	return v.watchKeyValueConfigOnChannel()
 }
 
 func (v *Viper) insensitiviseMaps() {
@@ -1298,6 +1536,23 @@ func (v *Viper) getRemoteConfig(provider RemoteProvider) (map[string]interface{}
 	return v.kvstore, err
 }
 
+// Retrieve the first found remote configuration.
+func (v *Viper) watchKeyValueConfigOnChannel() error {
+	for _, rp := range v.remoteProviders {
+		respc, _ := RemoteConfig.WatchChannel(rp)
+		//Todo: Add quit channel
+		go func(rc <-chan *RemoteResponse) {
+			for {
+				b := <-rc
+				reader := bytes.NewReader(b.Value)
+				v.unmarshalReader(reader, v.kvstore)
+			}
+		}(respc)
+		return nil
+	}
+	return RemoteConfigError("No Files Found")
+}
+
 // Retrieve the first found remote configuration.
 func (v *Viper) watchKeyValueConfig() error {
 	for _, rp := range v.remoteProviders {
@@ -1467,25 +1722,21 @@ func (v *Viper) getConfigType() string {
 }
 
 func (v *Viper) getConfigFile() (string, error) {
-	// if explicitly set, then use it
-	if v.configFile != "" {
-		return v.configFile, nil
+	if v.configFile == "" {
+		cf, err := v.findConfigFile()
+		if err != nil {
+			return "", err
+		}
+		v.configFile = cf
 	}
-
-	cf, err := v.findConfigFile()
-	if err != nil {
-		return "", err
-	}
-
-	v.configFile = cf
-	return v.getConfigFile()
+	return v.configFile, nil
 }
 
 func (v *Viper) searchInPath(in string) (filename string) {
 	jww.DEBUG.Println("Searching for config in ", in)
 	for _, ext := range SupportedExts {
 		jww.DEBUG.Println("Checking for", filepath.Join(in, v.configName+"."+ext))
-		if b, _ := exists(filepath.Join(in, v.configName+"."+ext)); b {
+		if b, _ := exists(v.fs, filepath.Join(in, v.configName+"."+ext)); b {
 			jww.DEBUG.Println("Found: ", filepath.Join(in, v.configName+"."+ext))
 			return filepath.Join(in, v.configName+"."+ext)
 		}
@@ -1497,7 +1748,6 @@ func (v *Viper) searchInPath(in string) (filename string) {
 // Search all configPaths for any config file.
 // Returns the first path that exists (and is a config file).
 func (v *Viper) findConfigFile() (string, error) {
-
 	jww.INFO.Println("Searching for config in ", v.configPaths)
 
 	for _, cp := range v.configPaths {

viper_test.go

@@ -18,6 +18,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/spf13/afero"
 	"github.com/spf13/cast"
 
 	"github.com/spf13/pflag"
@@ -262,7 +263,7 @@ func TestDefault(t *testing.T) {
 	assert.Equal(t, "leather", Get("clothing.jacket"))
 }
 
-func TestUnmarshalling(t *testing.T) {
+func TestUnmarshaling(t *testing.T) {
 	SetConfigType("yaml")
 	r := bytes.NewReader(yamlExample)
 
@@ -417,7 +418,7 @@ func TestAutoEnvWithPrefix(t *testing.T) {
 	assert.Equal(t, "13", Get("bar"))
 }
 
-func TestSetEnvReplacer(t *testing.T) {
+func TestSetEnvKeyReplacer(t *testing.T) {
 	Reset()
 
 	AutomaticEnv()
@@ -538,6 +539,44 @@ func TestBindPFlags(t *testing.T) {
 
 }
 
+func TestBindPFlagsStringSlice(t *testing.T) {
+	for _, testValue := range []struct {
+		Expected []string
+		Value    string
+	}{
+		{[]string{}, ""},
+		{[]string{"jeden"}, "jeden"},
+		{[]string{"dwa", "trzy"}, "dwa,trzy"},
+		{[]string{"cztery", "piec , szesc"}, "cztery,\"piec , szesc\""}} {
+
+		for _, changed := range []bool{true, false} {
+			v := New() // create independent Viper object
+			flagSet := pflag.NewFlagSet("test", pflag.ContinueOnError)
+			flagSet.StringSlice("stringslice", testValue.Expected, "test")
+			flagSet.Visit(func(f *pflag.Flag) {
+				if len(testValue.Value) > 0 {
+					f.Value.Set(testValue.Value)
+					f.Changed = changed
+				}
+			})
+
+			err := v.BindPFlags(flagSet)
+			if err != nil {
+				t.Fatalf("error binding flag set, %v", err)
+			}
+
+			type TestStr struct {
+				StringSlice []string
+			}
+			val := &TestStr{}
+			if err := v.Unmarshal(val); err != nil {
+				t.Fatalf("%+#v cannot unmarshal: %s", testValue.Value, err)
+			}
+			assert.Equal(t, testValue.Expected, val.StringSlice)
+		}
+	}
+}
+
 func TestBindPFlag(t *testing.T) {
 	var testString = "testing"
 	var testValue = newStringValue(testString, &testString)
@@ -809,6 +848,190 @@ func TestSub(t *testing.T) {
 	assert.Equal(t, (*Viper)(nil), subv)
 }
 
+var hclWriteExpected = []byte(`"foos" = {
+  "foo" = {
+    "key" = 1
+  }
+
+  "foo" = {
+    "key" = 2
+  }
+
+  "foo" = {
+    "key" = 3
+  }
+
+  "foo" = {
+    "key" = 4
+  }
+}
+
+"id" = "0001"
+
+"name" = "Cake"
+
+"ppu" = 0.55
+
+"type" = "donut"`)
+
+func TestWriteConfigHCL(t *testing.T) {
+	v := New()
+	fs := afero.NewMemMapFs()
+	v.SetFs(fs)
+	v.SetConfigName("c")
+	v.SetConfigType("hcl")
+	err := v.ReadConfig(bytes.NewBuffer(hclExample))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := v.WriteConfigAs("c.hcl"); err != nil {
+		t.Fatal(err)
+	}
+	read, err := afero.ReadFile(fs, "c.hcl")
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, hclWriteExpected, read)
+}
+
+var jsonWriteExpected = []byte(`{
+  "batters": {
+    "batter": [
+      {
+        "type": "Regular"
+      },
+      {
+        "type": "Chocolate"
+      },
+      {
+        "type": "Blueberry"
+      },
+      {
+        "type": "Devil's Food"
+      }
+    ]
+  },
+  "id": "0001",
+  "name": "Cake",
+  "ppu": 0.55,
+  "type": "donut"
+}`)
+
+func TestWriteConfigJson(t *testing.T) {
+	v := New()
+	fs := afero.NewMemMapFs()
+	v.SetFs(fs)
+	v.SetConfigName("c")
+	v.SetConfigType("json")
+	err := v.ReadConfig(bytes.NewBuffer(jsonExample))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := v.WriteConfigAs("c.json"); err != nil {
+		t.Fatal(err)
+	}
+	read, err := afero.ReadFile(fs, "c.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, jsonWriteExpected, read)
+}
+
+var propertiesWriteExpected = []byte(`p_id = 0001
+p_type = donut
+p_name = Cake
+p_ppu = 0.55
+p_batters.batter.type = Regular
+`)
+
+func TestWriteConfigProperties(t *testing.T) {
+	v := New()
+	fs := afero.NewMemMapFs()
+	v.SetFs(fs)
+	v.SetConfigName("c")
+	v.SetConfigType("properties")
+	err := v.ReadConfig(bytes.NewBuffer(propertiesExample))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := v.WriteConfigAs("c.properties"); err != nil {
+		t.Fatal(err)
+	}
+	read, err := afero.ReadFile(fs, "c.properties")
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, propertiesWriteExpected, read)
+}
+
+func TestWriteConfigTOML(t *testing.T) {
+	fs := afero.NewMemMapFs()
+	v := New()
+	v.SetFs(fs)
+	v.SetConfigName("c")
+	v.SetConfigType("toml")
+	err := v.ReadConfig(bytes.NewBuffer(tomlExample))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := v.WriteConfigAs("c.toml"); err != nil {
+		t.Fatal(err)
+	}
+
+	// The TOML String method does not order the contents.
+	// Therefore, we must read the generated file and compare the data.
+	v2 := New()
+	v2.SetFs(fs)
+	v2.SetConfigName("c")
+	v2.SetConfigType("toml")
+	v2.SetConfigFile("c.toml")
+	err = v2.ReadInConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, v.GetString("title"), v2.GetString("title"))
+	assert.Equal(t, v.GetString("owner.bio"), v2.GetString("owner.bio"))
+	assert.Equal(t, v.GetString("owner.dob"), v2.GetString("owner.dob"))
+	assert.Equal(t, v.GetString("owner.organization"), v2.GetString("owner.organization"))
+}
+
+var yamlWriteExpected = []byte(`age: 35
+beard: true
+clothing:
+  jacket: leather
+  pants:
+    size: large
+  trousers: denim
+eyes: brown
+hacker: true
+hobbies:
+- skateboarding
+- snowboarding
+- go
+name: steve
+`)
+
+func TestWriteConfigYAML(t *testing.T) {
+	v := New()
+	fs := afero.NewMemMapFs()
+	v.SetFs(fs)
+	v.SetConfigName("c")
+	v.SetConfigType("yaml")
+	err := v.ReadConfig(bytes.NewBuffer(yamlExample))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := v.WriteConfigAs("c.yaml"); err != nil {
+		t.Fatal(err)
+	}
+	read, err := afero.ReadFile(fs, "c.yaml")
+	if err != nil {
+		t.Fatal(err)
+	}
+	assert.Equal(t, yamlWriteExpected, read)
+}
+
 var yamlMergeExampleTgt = []byte(`
 hello:
     pop: 37890
@@ -1102,6 +1325,35 @@ func TestCaseInsensitiveSet(t *testing.T) {
 	}
 }
 
+func TestParseNested(t *testing.T) {
+	type duration struct {
+		Delay time.Duration
+	}
+
+	type item struct {
+		Name   string
+		Delay  time.Duration
+		Nested duration
+	}
+
+	config := `[[parent]]
+	delay="100ms"
+	[parent.nested]
+	delay="200ms"
+`
+	initConfig("toml", config)
+
+	var items []item
+	err := v.UnmarshalKey("parent", &items)
+	if err != nil {
+		t.Fatalf("unable to decode into struct, %v", err)
+	}
+
+	assert.Equal(t, 1, len(items))
+	assert.Equal(t, 100*time.Millisecond, items[0].Delay)
+	assert.Equal(t, 200*time.Millisecond, items[0].Nested.Delay)
+}
+
 func doTestCaseInsensitive(t *testing.T, typ, config string) {
 	initConfig(typ, config)
 	Set("RfD", true)