Update to add build contraints to not compile in yaml support

in the case the golang version is less than golang 1.2

altsrc/flag.go

@@ -0,0 +1,439 @@
+package altsrc
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/codegangsta/cli"
+)
+
+// FlagInputSourceExtension is an extension interface of cli.Flag that
+// allows a value to be set on the existing parsed flags.
+type FlagInputSourceExtension interface {
+	cli.Flag
+	ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error
+}
+
+// ApplyInputSourceValues iterates over all provided flags and
+// executes ApplyInputSourceValue on flags implementing the
+// FlagInputSourceExtension interface to initialize these flags
+// to an alternate input source.
+func ApplyInputSourceValues(context *cli.Context, inputSourceContext InputSourceContext, flags []cli.Flag) error {
+	for _, f := range flags {
+		inputSourceExtendedFlag, isType := f.(FlagInputSourceExtension)
+		if isType {
+			err := inputSourceExtendedFlag.ApplyInputSourceValue(context, inputSourceContext)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+// InitInputSource is used to to setup an InputSourceContext on a cli.Command Before method. It will create a new
+// input source based on the func provided. If there is no error it will then apply the new input source to any flags
+// that are supported by the input source
+func InitInputSource(flags []cli.Flag, createInputSource func() (InputSourceContext, error)) func(context *cli.Context) error {
+	return func(context *cli.Context) error {
+		inputSource, err := createInputSource()
+		if err != nil {
+			return fmt.Errorf("Unable to create input source: inner error: \n'%v'", err.Error())
+		}
+
+		return ApplyInputSourceValues(context, inputSource, flags)
+	}
+}
+
+// InitInputSourceWithContext is used to to setup an InputSourceContext on a cli.Command Before method. It will create a new
+// input source based on the func provided with potentially using existing cli.Context values to initialize itself. If there is
+// no error it will then apply the new input source to any flags that are supported by the input source
+func InitInputSourceWithContext(flags []cli.Flag, createInputSource func(context *cli.Context) (InputSourceContext, error)) func(context *cli.Context) error {
+	return func(context *cli.Context) error {
+		inputSource, err := createInputSource(context)
+		if err != nil {
+			return fmt.Errorf("Unable to create input source with context: inner error: \n'%v'", err.Error())
+		}
+
+		return ApplyInputSourceValues(context, inputSource, flags)
+	}
+}
+
+// GenericFlag is the flag type that wraps cli.GenericFlag to allow
+// for other values to be specified
+type GenericFlag struct {
+	cli.GenericFlag
+	set *flag.FlagSet
+}
+
+// NewGenericFlag creates a new GenericFlag
+func NewGenericFlag(flag cli.GenericFlag) *GenericFlag {
+	return &GenericFlag{GenericFlag: flag, set: nil}
+}
+
+// ApplyInputSourceValue applies a generic value to the flagSet if required
+func (f *GenericFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+	if f.set != nil {
+		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
+			value, err := isc.Generic(f.GenericFlag.Name)
+			if err != nil {
+				return err
+			}
+			if value != nil {
+				eachName(f.Name, func(name string) {
+					f.set.Set(f.Name, value.String())
+				})
+			}
+		}
+	}
+
+	return nil
+}
+
+// Apply saves the flagSet for later usage then calls
+// the wrapped GenericFlag.Apply
+func (f *GenericFlag) Apply(set *flag.FlagSet) {
+	f.set = set
+	f.GenericFlag.Apply(set)
+}
+
+// StringSliceFlag is the flag type that wraps cli.StringSliceFlag to allow
+// for other values to be specified
+type StringSliceFlag struct {
+	cli.StringSliceFlag
+	set *flag.FlagSet
+}
+
+// NewStringSliceFlag creates a new StringSliceFlag
+func NewStringSliceFlag(flag cli.StringSliceFlag) *StringSliceFlag {
+	return &StringSliceFlag{StringSliceFlag: flag, set: nil}
+}
+
+// ApplyInputSourceValue applies a StringSlice value to the flagSet if required
+func (f *StringSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+	if f.set != nil {
+		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
+			value, err := isc.StringSlice(f.StringSliceFlag.Name)
+			if err != nil {
+				return err
+			}
+			if value != nil {
+				var sliceValue cli.StringSlice = value
+				eachName(f.Name, func(name string) {
+					underlyingFlag := f.set.Lookup(f.Name)
+					if underlyingFlag != nil {
+						underlyingFlag.Value = &sliceValue
+					}
+				})
+			}
+		}
+	}
+	return nil
+}
+
+// Apply saves the flagSet for later usage then calls
+// the wrapped StringSliceFlag.Apply
+func (f *StringSliceFlag) Apply(set *flag.FlagSet) {
+	f.set = set
+	f.StringSliceFlag.Apply(set)
+}
+
+// IntSliceFlag is the flag type that wraps cli.IntSliceFlag to allow
+// for other values to be specified
+type IntSliceFlag struct {
+	cli.IntSliceFlag
+	set *flag.FlagSet
+}
+
+// NewIntSliceFlag creates a new IntSliceFlag
+func NewIntSliceFlag(flag cli.IntSliceFlag) *IntSliceFlag {
+	return &IntSliceFlag{IntSliceFlag: flag, set: nil}
+}
+
+// ApplyInputSourceValue applies a IntSlice value if required
+func (f *IntSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+	if f.set != nil {
+		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
+			value, err := isc.IntSlice(f.IntSliceFlag.Name)
+			if err != nil {
+				return err
+			}
+			if value != nil {
+				var sliceValue cli.IntSlice = value
+				eachName(f.Name, func(name string) {
+					underlyingFlag := f.set.Lookup(f.Name)
+					if underlyingFlag != nil {
+						underlyingFlag.Value = &sliceValue
+					}
+				})
+			}
+		}
+	}
+	return nil
+}
+
+// Apply saves the flagSet for later usage then calls
+// the wrapped IntSliceFlag.Apply
+func (f *IntSliceFlag) Apply(set *flag.FlagSet) {
+	f.set = set
+	f.IntSliceFlag.Apply(set)
+}
+
+// BoolFlag is the flag type that wraps cli.BoolFlag to allow
+// for other values to be specified
+type BoolFlag struct {
+	cli.BoolFlag
+	set *flag.FlagSet
+}
+
+// NewBoolFlag creates a new BoolFlag
+func NewBoolFlag(flag cli.BoolFlag) *BoolFlag {
+	return &BoolFlag{BoolFlag: flag, set: nil}
+}
+
+// ApplyInputSourceValue applies a Bool value to the flagSet if required
+func (f *BoolFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+	if f.set != nil {
+		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
+			value, err := isc.Bool(f.BoolFlag.Name)
+			if err != nil {
+				return err
+			}
+			if value {
+				eachName(f.Name, func(name string) {
+					f.set.Set(f.Name, strconv.FormatBool(value))
+				})
+			}
+		}
+	}
+	return nil
+}
+
+// Apply saves the flagSet for later usage then calls
+// the wrapped BoolFlag.Apply
+func (f *BoolFlag) Apply(set *flag.FlagSet) {
+	f.set = set
+	f.BoolFlag.Apply(set)
+}
+
+// BoolTFlag is the flag type that wraps cli.BoolTFlag to allow
+// for other values to be specified
+type BoolTFlag struct {
+	cli.BoolTFlag
+	set *flag.FlagSet
+}
+
+// NewBoolTFlag creates a new BoolTFlag
+func NewBoolTFlag(flag cli.BoolTFlag) *BoolTFlag {
+	return &BoolTFlag{BoolTFlag: flag, set: nil}
+}
+
+// ApplyInputSourceValue applies a BoolT value to the flagSet if required
+func (f *BoolTFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+	if f.set != nil {
+		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
+			value, err := isc.BoolT(f.BoolTFlag.Name)
+			if err != nil {
+				return err
+			}
+			if !value {
+				eachName(f.Name, func(name string) {
+					f.set.Set(f.Name, strconv.FormatBool(value))
+				})
+			}
+		}
+	}
+	return nil
+}
+
+// Apply saves the flagSet for later usage then calls
+// the wrapped BoolTFlag.Apply
+func (f *BoolTFlag) Apply(set *flag.FlagSet) {
+	f.set = set
+
+	f.BoolTFlag.Apply(set)
+}
+
+// StringFlag is the flag type that wraps cli.StringFlag to allow
+// for other values to be specified
+type StringFlag struct {
+	cli.StringFlag
+	set *flag.FlagSet
+}
+
+// NewStringFlag creates a new StringFlag
+func NewStringFlag(flag cli.StringFlag) *StringFlag {
+	return &StringFlag{StringFlag: flag, set: nil}
+}
+
+// ApplyInputSourceValue applies a String value to the flagSet if required
+func (f *StringFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+	if f.set != nil {
+		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVar)) {
+			value, err := isc.String(f.StringFlag.Name)
+			if err != nil {
+				return err
+			}
+			if value != "" {
+				eachName(f.Name, func(name string) {
+					f.set.Set(f.Name, value)
+				})
+			}
+		}
+	}
+	return nil
+}
+
+// Apply saves the flagSet for later usage then calls
+// the wrapped StringFlag.Apply
+func (f *StringFlag) Apply(set *flag.FlagSet) {
+	f.set = set
+
+	f.StringFlag.Apply(set)
+}
+
+// IntFlag is the flag type that wraps cli.IntFlag to allow
+// for other values to be specified
+type IntFlag struct {
+	cli.IntFlag
+	set *flag.FlagSet
+}
+
+// NewIntFlag creates a new IntFlag
+func NewIntFlag(flag cli.IntFlag) *IntFlag {
+	return &IntFlag{IntFlag: flag, set: nil}
+}
+
+// ApplyInputSourceValue applies a int value to the flagSet if required
+func (f *IntFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+	if f.set != nil {
+		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVar)) {
+			value, err := isc.Int(f.IntFlag.Name)
+			if err != nil {
+				return err
+			}
+			if value > 0 {
+				eachName(f.Name, func(name string) {
+					f.set.Set(f.Name, strconv.FormatInt(int64(value), 10))
+				})
+			}
+		}
+	}
+	return nil
+}
+
+// Apply saves the flagSet for later usage then calls
+// the wrapped IntFlag.Apply
+func (f *IntFlag) Apply(set *flag.FlagSet) {
+	f.set = set
+	f.IntFlag.Apply(set)
+}
+
+// DurationFlag is the flag type that wraps cli.DurationFlag to allow
+// for other values to be specified
+type DurationFlag struct {
+	cli.DurationFlag
+	set *flag.FlagSet
+}
+
+// NewDurationFlag creates a new DurationFlag
+func NewDurationFlag(flag cli.DurationFlag) *DurationFlag {
+	return &DurationFlag{DurationFlag: flag, set: nil}
+}
+
+// ApplyInputSourceValue applies a Duration value to the flagSet if required
+func (f *DurationFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+	if f.set != nil {
+		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVar)) {
+			value, err := isc.Duration(f.DurationFlag.Name)
+			if err != nil {
+				return err
+			}
+			if value > 0 {
+				eachName(f.Name, func(name string) {
+					f.set.Set(f.Name, value.String())
+				})
+			}
+		}
+	}
+	return nil
+}
+
+// Apply saves the flagSet for later usage then calls
+// the wrapped DurationFlag.Apply
+func (f *DurationFlag) Apply(set *flag.FlagSet) {
+	f.set = set
+
+	f.DurationFlag.Apply(set)
+}
+
+// Float64Flag is the flag type that wraps cli.Float64Flag to allow
+// for other values to be specified
+type Float64Flag struct {
+	cli.Float64Flag
+	set *flag.FlagSet
+}
+
+// NewFloat64Flag creates a new Float64Flag
+func NewFloat64Flag(flag cli.Float64Flag) *Float64Flag {
+	return &Float64Flag{Float64Flag: flag, set: nil}
+}
+
+// ApplyInputSourceValue applies a Float64 value to the flagSet if required
+func (f *Float64Flag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
+	if f.set != nil {
+		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVar)) {
+			value, err := isc.Float64(f.Float64Flag.Name)
+			if err != nil {
+				return err
+			}
+			if value > 0 {
+				floatStr := float64ToString(value)
+				eachName(f.Name, func(name string) {
+					f.set.Set(f.Name, floatStr)
+				})
+			}
+		}
+	}
+	return nil
+}
+
+// Apply saves the flagSet for later usage then calls
+// the wrapped Float64Flag.Apply
+func (f *Float64Flag) Apply(set *flag.FlagSet) {
+	f.set = set
+
+	f.Float64Flag.Apply(set)
+}
+
+func isEnvVarSet(envVars string) bool {
+	for _, envVar := range strings.Split(envVars, ",") {
+		envVar = strings.TrimSpace(envVar)
+		if envVal := os.Getenv(envVar); envVal != "" {
+			// TODO: Can't use this for bools as
+			// set means that it was true or false based on
+			// Bool flag type, should work for other types
+			if len(envVal) > 0 {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+func float64ToString(f float64) string {
+	return fmt.Sprintf("%v", f)
+}
+
+func eachName(longName string, fn func(string)) {
+	parts := strings.Split(longName, ",")
+	for _, name := range parts {
+		name = strings.Trim(name, " ")
+		fn(name)
+	}
+}

altsrc/flag_test.go

@@ -0,0 +1,336 @@
+package altsrc
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/codegangsta/cli"
+)
+
+type testApplyInputSource struct {
+	Flag               FlagInputSourceExtension
+	FlagName           string
+	FlagSetName        string
+	Expected           string
+	ContextValueString string
+	ContextValue       flag.Value
+	EnvVarValue        string
+	EnvVarName         string
+	MapValue           interface{}
+}
+
+func TestGenericApplyInputSourceValue(t *testing.T) {
+	v := &Parser{"abc", "def"}
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewGenericFlag(cli.GenericFlag{Name: "test", Value: &Parser{}}),
+		FlagName: "test",
+		MapValue: v,
+	})
+	expect(t, v, c.Generic("test"))
+}
+
+func TestGenericApplyInputSourceMethodContextSet(t *testing.T) {
+	p := &Parser{"abc", "def"}
+	c := runTest(t, testApplyInputSource{
+		Flag:               NewGenericFlag(cli.GenericFlag{Name: "test", Value: &Parser{}}),
+		FlagName:           "test",
+		MapValue:           &Parser{"efg", "hig"},
+		ContextValueString: p.String(),
+	})
+	expect(t, p, c.Generic("test"))
+}
+
+func TestGenericApplyInputSourceMethodEnvVarSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:        NewGenericFlag(cli.GenericFlag{Name: "test", Value: &Parser{}, EnvVar: "TEST"}),
+		FlagName:    "test",
+		MapValue:    &Parser{"efg", "hij"},
+		EnvVarName:  "TEST",
+		EnvVarValue: "abc,def",
+	})
+	expect(t, &Parser{"abc", "def"}, c.Generic("test"))
+}
+
+func TestStringSliceApplyInputSourceValue(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewStringSliceFlag(cli.StringSliceFlag{Name: "test"}),
+		FlagName: "test",
+		MapValue: []string{"hello", "world"},
+	})
+	expect(t, c.StringSlice("test"), []string{"hello", "world"})
+}
+
+func TestStringSliceApplyInputSourceMethodContextSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:               NewStringSliceFlag(cli.StringSliceFlag{Name: "test"}),
+		FlagName:           "test",
+		MapValue:           []string{"hello", "world"},
+		ContextValueString: "ohno",
+	})
+	expect(t, c.StringSlice("test"), []string{"ohno"})
+}
+
+func TestStringSliceApplyInputSourceMethodEnvVarSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:        NewStringSliceFlag(cli.StringSliceFlag{Name: "test", EnvVar: "TEST"}),
+		FlagName:    "test",
+		MapValue:    []string{"hello", "world"},
+		EnvVarName:  "TEST",
+		EnvVarValue: "oh,no",
+	})
+	expect(t, c.StringSlice("test"), []string{"oh", "no"})
+}
+
+func TestIntSliceApplyInputSourceValue(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewIntSliceFlag(cli.IntSliceFlag{Name: "test"}),
+		FlagName: "test",
+		MapValue: []int{1, 2},
+	})
+	expect(t, c.IntSlice("test"), []int{1, 2})
+}
+
+func TestIntSliceApplyInputSourceMethodContextSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:               NewIntSliceFlag(cli.IntSliceFlag{Name: "test"}),
+		FlagName:           "test",
+		MapValue:           []int{1, 2},
+		ContextValueString: "3",
+	})
+	expect(t, c.IntSlice("test"), []int{3})
+}
+
+func TestIntSliceApplyInputSourceMethodEnvVarSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:        NewIntSliceFlag(cli.IntSliceFlag{Name: "test", EnvVar: "TEST"}),
+		FlagName:    "test",
+		MapValue:    []int{1, 2},
+		EnvVarName:  "TEST",
+		EnvVarValue: "3,4",
+	})
+	expect(t, c.IntSlice("test"), []int{3, 4})
+}
+
+func TestBoolApplyInputSourceMethodSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewBoolFlag(cli.BoolFlag{Name: "test"}),
+		FlagName: "test",
+		MapValue: true,
+	})
+	expect(t, true, c.Bool("test"))
+}
+
+func TestBoolApplyInputSourceMethodContextSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:               NewBoolFlag(cli.BoolFlag{Name: "test"}),
+		FlagName:           "test",
+		MapValue:           false,
+		ContextValueString: "true",
+	})
+	expect(t, true, c.Bool("test"))
+}
+
+func TestBoolApplyInputSourceMethodEnvVarSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:        NewBoolFlag(cli.BoolFlag{Name: "test", EnvVar: "TEST"}),
+		FlagName:    "test",
+		MapValue:    false,
+		EnvVarName:  "TEST",
+		EnvVarValue: "true",
+	})
+	expect(t, true, c.Bool("test"))
+}
+
+func TestBoolTApplyInputSourceMethodSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewBoolTFlag(cli.BoolTFlag{Name: "test"}),
+		FlagName: "test",
+		MapValue: false,
+	})
+	expect(t, false, c.BoolT("test"))
+}
+
+func TestBoolTApplyInputSourceMethodContextSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:               NewBoolTFlag(cli.BoolTFlag{Name: "test"}),
+		FlagName:           "test",
+		MapValue:           true,
+		ContextValueString: "false",
+	})
+	expect(t, false, c.BoolT("test"))
+}
+
+func TestBoolTApplyInputSourceMethodEnvVarSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:        NewBoolTFlag(cli.BoolTFlag{Name: "test", EnvVar: "TEST"}),
+		FlagName:    "test",
+		MapValue:    true,
+		EnvVarName:  "TEST",
+		EnvVarValue: "false",
+	})
+	expect(t, false, c.BoolT("test"))
+}
+
+func TestStringApplyInputSourceMethodSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewStringFlag(cli.StringFlag{Name: "test"}),
+		FlagName: "test",
+		MapValue: "hello",
+	})
+	expect(t, "hello", c.String("test"))
+}
+
+func TestStringApplyInputSourceMethodContextSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:               NewStringFlag(cli.StringFlag{Name: "test"}),
+		FlagName:           "test",
+		MapValue:           "hello",
+		ContextValueString: "goodbye",
+	})
+	expect(t, "goodbye", c.String("test"))
+}
+
+func TestStringApplyInputSourceMethodEnvVarSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:        NewStringFlag(cli.StringFlag{Name: "test", EnvVar: "TEST"}),
+		FlagName:    "test",
+		MapValue:    "hello",
+		EnvVarName:  "TEST",
+		EnvVarValue: "goodbye",
+	})
+	expect(t, "goodbye", c.String("test"))
+}
+
+func TestIntApplyInputSourceMethodSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewIntFlag(cli.IntFlag{Name: "test"}),
+		FlagName: "test",
+		MapValue: 15,
+	})
+	expect(t, 15, c.Int("test"))
+}
+
+func TestIntApplyInputSourceMethodContextSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:               NewIntFlag(cli.IntFlag{Name: "test"}),
+		FlagName:           "test",
+		MapValue:           15,
+		ContextValueString: "7",
+	})
+	expect(t, 7, c.Int("test"))
+}
+
+func TestIntApplyInputSourceMethodEnvVarSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:        NewIntFlag(cli.IntFlag{Name: "test", EnvVar: "TEST"}),
+		FlagName:    "test",
+		MapValue:    15,
+		EnvVarName:  "TEST",
+		EnvVarValue: "12",
+	})
+	expect(t, 12, c.Int("test"))
+}
+
+func TestDurationApplyInputSourceMethodSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewDurationFlag(cli.DurationFlag{Name: "test"}),
+		FlagName: "test",
+		MapValue: time.Duration(30 * time.Second),
+	})
+	expect(t, time.Duration(30*time.Second), c.Duration("test"))
+}
+
+func TestDurationApplyInputSourceMethodContextSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:               NewDurationFlag(cli.DurationFlag{Name: "test"}),
+		FlagName:           "test",
+		MapValue:           time.Duration(30 * time.Second),
+		ContextValueString: time.Duration(15 * time.Second).String(),
+	})
+	expect(t, time.Duration(15*time.Second), c.Duration("test"))
+}
+
+func TestDurationApplyInputSourceMethodEnvVarSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:        NewDurationFlag(cli.DurationFlag{Name: "test", EnvVar: "TEST"}),
+		FlagName:    "test",
+		MapValue:    time.Duration(30 * time.Second),
+		EnvVarName:  "TEST",
+		EnvVarValue: time.Duration(15 * time.Second).String(),
+	})
+	expect(t, time.Duration(15*time.Second), c.Duration("test"))
+}
+
+func TestFloat64ApplyInputSourceMethodSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:     NewFloat64Flag(cli.Float64Flag{Name: "test"}),
+		FlagName: "test",
+		MapValue: 1.3,
+	})
+	expect(t, 1.3, c.Float64("test"))
+}
+
+func TestFloat64ApplyInputSourceMethodContextSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:               NewFloat64Flag(cli.Float64Flag{Name: "test"}),
+		FlagName:           "test",
+		MapValue:           1.3,
+		ContextValueString: fmt.Sprintf("%v", 1.4),
+	})
+	expect(t, 1.4, c.Float64("test"))
+}
+
+func TestFloat64ApplyInputSourceMethodEnvVarSet(t *testing.T) {
+	c := runTest(t, testApplyInputSource{
+		Flag:        NewFloat64Flag(cli.Float64Flag{Name: "test", EnvVar: "TEST"}),
+		FlagName:    "test",
+		MapValue:    1.3,
+		EnvVarName:  "TEST",
+		EnvVarValue: fmt.Sprintf("%v", 1.4),
+	})
+	expect(t, 1.4, c.Float64("test"))
+}
+
+func runTest(t *testing.T, test testApplyInputSource) *cli.Context {
+	inputSource := &MapInputSource{valueMap: map[string]interface{}{test.FlagName: test.MapValue}}
+	set := flag.NewFlagSet(test.FlagSetName, flag.ContinueOnError)
+	c := cli.NewContext(nil, set, nil)
+	if test.EnvVarName != "" && test.EnvVarValue != "" {
+		os.Setenv(test.EnvVarName, test.EnvVarValue)
+		defer os.Setenv(test.EnvVarName, "")
+	}
+
+	test.Flag.Apply(set)
+	if test.ContextValue != nil {
+		flag := set.Lookup(test.FlagName)
+		flag.Value = test.ContextValue
+	}
+	if test.ContextValueString != "" {
+		set.Set(test.FlagName, test.ContextValueString)
+	}
+	test.Flag.ApplyInputSourceValue(c, inputSource)
+
+	return c
+}
+
+type Parser [2]string
+
+func (p *Parser) Set(value string) error {
+	parts := strings.Split(value, ",")
+	if len(parts) != 2 {
+		return fmt.Errorf("invalid format")
+	}
+
+	(*p)[0] = parts[0]
+	(*p)[1] = parts[1]
+
+	return nil
+}
+
+func (p *Parser) String() string {
+	return fmt.Sprintf("%s,%s", p[0], p[1])
+}

altsrc/helpers_test.go

@@ -0,0 +1,18 @@
+package altsrc
+
+import (
+	"reflect"
+	"testing"
+)
+
+func expect(t *testing.T, a interface{}, b interface{}) {
+	if !reflect.DeepEqual(b, a) {
+		t.Errorf("Expected %#v (type %v) - Got %#v (type %v)", b, reflect.TypeOf(b), a, reflect.TypeOf(a))
+	}
+}
+
+func refute(t *testing.T, a interface{}, b interface{}) {
+	if a == b {
+		t.Errorf("Did not expect %v (type %v) - Got %v (type %v)", b, reflect.TypeOf(b), a, reflect.TypeOf(a))
+	}
+}

altsrc/input_source_context.go

@@ -0,0 +1,21 @@
+package altsrc
+
+import (
+	"time"
+
+	"github.com/codegangsta/cli"
+)
+
+// InputSourceContext is an interface used to allow
+// other input sources to be implemented as needed.
+type InputSourceContext interface {
+	Int(name string) (int, error)
+	Duration(name string) (time.Duration, error)
+	Float64(name string) (float64, error)
+	String(name string) (string, error)
+	StringSlice(name string) ([]string, error)
+	IntSlice(name string) ([]int, error)
+	Generic(name string) (cli.Generic, error)
+	Bool(name string) (bool, error)
+	BoolT(name string) (bool, error)
+}

altsrc/map_input_source.go

@@ -0,0 +1,152 @@
+package altsrc
+
+import (
+	"fmt"
+	"reflect"
+	"time"
+
+	"github.com/codegangsta/cli"
+)
+
+// MapInputSource implements InputSourceContext to return
+// data from the map that is loaded.
+type MapInputSource struct {
+	valueMap map[string]interface{}
+}
+
+// Int returns an int from the map if it exists otherwise returns 0
+func (fsm *MapInputSource) Int(name string) (int, error) {
+	otherGenericValue, exists := fsm.valueMap[name]
+	if exists {
+		otherValue, isType := otherGenericValue.(int)
+		if !isType {
+			return 0, incorrectTypeForFlagError(name, "int", otherGenericValue)
+		}
+
+		return otherValue, nil
+	}
+
+	return 0, nil
+}
+
+// Duration returns a duration from the map if it exists otherwise returns 0
+func (fsm *MapInputSource) Duration(name string) (time.Duration, error) {
+	otherGenericValue, exists := fsm.valueMap[name]
+	if exists {
+		otherValue, isType := otherGenericValue.(time.Duration)
+		if !isType {
+			return 0, incorrectTypeForFlagError(name, "duration", otherGenericValue)
+		}
+		return otherValue, nil
+	}
+
+	return 0, nil
+}
+
+// Float64 returns an float64 from the map if it exists otherwise returns 0
+func (fsm *MapInputSource) Float64(name string) (float64, error) {
+	otherGenericValue, exists := fsm.valueMap[name]
+	if exists {
+		otherValue, isType := otherGenericValue.(float64)
+		if !isType {
+			return 0, incorrectTypeForFlagError(name, "float64", otherGenericValue)
+		}
+		return otherValue, nil
+	}
+
+	return 0, nil
+}
+
+// String returns a string from the map if it exists otherwise returns an empty string
+func (fsm *MapInputSource) String(name string) (string, error) {
+	otherGenericValue, exists := fsm.valueMap[name]
+	if exists {
+		otherValue, isType := otherGenericValue.(string)
+		if !isType {
+			return "", incorrectTypeForFlagError(name, "string", otherGenericValue)
+		}
+		return otherValue, nil
+	}
+
+	return "", nil
+}
+
+// StringSlice returns an []string from the map if it exists otherwise returns nil
+func (fsm *MapInputSource) StringSlice(name string) ([]string, error) {
+	otherGenericValue, exists := fsm.valueMap[name]
+	if exists {
+		otherValue, isType := otherGenericValue.([]string)
+		if !isType {
+			return nil, incorrectTypeForFlagError(name, "[]string", otherGenericValue)
+		}
+		return otherValue, nil
+	}
+
+	return nil, nil
+}
+
+// IntSlice returns an []int from the map if it exists otherwise returns nil
+func (fsm *MapInputSource) IntSlice(name string) ([]int, error) {
+	otherGenericValue, exists := fsm.valueMap[name]
+	if exists {
+		otherValue, isType := otherGenericValue.([]int)
+		if !isType {
+			return nil, incorrectTypeForFlagError(name, "[]int", otherGenericValue)
+		}
+		return otherValue, nil
+	}
+
+	return nil, nil
+}
+
+// Generic returns an cli.Generic from the map if it exists otherwise returns nil
+func (fsm *MapInputSource) Generic(name string) (cli.Generic, error) {
+	otherGenericValue, exists := fsm.valueMap[name]
+	if exists {
+		otherValue, isType := otherGenericValue.(cli.Generic)
+		if !isType {
+			return nil, incorrectTypeForFlagError(name, "cli.Generic", otherGenericValue)
+		}
+		return otherValue, nil
+	}
+
+	return nil, nil
+}
+
+// Bool returns an bool from the map otherwise returns false
+func (fsm *MapInputSource) Bool(name string) (bool, error) {
+	otherGenericValue, exists := fsm.valueMap[name]
+	if exists {
+		otherValue, isType := otherGenericValue.(bool)
+		if !isType {
+			return false, incorrectTypeForFlagError(name, "bool", otherGenericValue)
+		}
+		return otherValue, nil
+	}
+
+	return false, nil
+}
+
+// BoolT returns an bool from the map otherwise returns true
+func (fsm *MapInputSource) BoolT(name string) (bool, error) {
+	otherGenericValue, exists := fsm.valueMap[name]
+	if exists {
+		otherValue, isType := otherGenericValue.(bool)
+		if !isType {
+			return true, incorrectTypeForFlagError(name, "bool", otherGenericValue)
+		}
+		return otherValue, nil
+	}
+
+	return true, nil
+}
+
+func incorrectTypeForFlagError(name, expectedTypeName string, value interface{}) error {
+	valueType := reflect.TypeOf(value)
+	valueTypeName := ""
+	if valueType != nil {
+		valueTypeName = valueType.Name()
+	}
+
+	return fmt.Errorf("Mismatched type for flag '%s'. Expected '%s' but actual is '%s'", name, expectedTypeName, valueTypeName)
+}

altsrc/yaml_command_test.go

@@ -0,0 +1,172 @@
+// Disabling building of yaml support in cases where golang is 1.0 or 1.1
+// as the encoding library is not implemented or supported.
+
+// +build !go1,!go1.1
+
+package altsrc
+
+import (
+	"flag"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/codegangsta/cli"
+)
+
+func TestCommandYamlFileTest(t *testing.T) {
+	app := cli.NewApp()
+	set := flag.NewFlagSet("test", 0)
+	ioutil.WriteFile("current.yaml", []byte("test: 15"), 0666)
+	defer os.Remove("current.yaml")
+	test := []string{"test-cmd", "--load", "current.yaml"}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) {
+			val := c.Int("test")
+			expect(t, val, 15)
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(cli.IntFlag{Name: "test"}),
+			cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandYamlFileTestGlobalEnvVarWins(t *testing.T) {
+	app := cli.NewApp()
+	set := flag.NewFlagSet("test", 0)
+	ioutil.WriteFile("current.yaml", []byte("test: 15"), 0666)
+	defer os.Remove("current.yaml")
+
+	os.Setenv("THE_TEST", "10")
+	defer os.Setenv("THE_TEST", "")
+	test := []string{"test-cmd", "--load", "current.yaml"}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) {
+			val := c.Int("test")
+			expect(t, val, 10)
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(cli.IntFlag{Name: "test", EnvVar: "THE_TEST"}),
+			cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
+
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandYamlFileTestSpecifiedFlagWins(t *testing.T) {
+	app := cli.NewApp()
+	set := flag.NewFlagSet("test", 0)
+	ioutil.WriteFile("current.yaml", []byte("test: 15"), 0666)
+	defer os.Remove("current.yaml")
+
+	test := []string{"test-cmd", "--load", "current.yaml", "--test", "7"}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) {
+			val := c.Int("test")
+			expect(t, val, 7)
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(cli.IntFlag{Name: "test"}),
+			cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
+
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandYamlFileTestDefaultValueFileWins(t *testing.T) {
+	app := cli.NewApp()
+	set := flag.NewFlagSet("test", 0)
+	ioutil.WriteFile("current.yaml", []byte("test: 15"), 0666)
+	defer os.Remove("current.yaml")
+
+	test := []string{"test-cmd", "--load", "current.yaml"}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) {
+			val := c.Int("test")
+			expect(t, val, 15)
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(cli.IntFlag{Name: "test", Value: 7}),
+			cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
+
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}
+
+func TestCommandYamlFileFlagHasDefaultGlobalEnvYamlSetGlobalEnvWins(t *testing.T) {
+	app := cli.NewApp()
+	set := flag.NewFlagSet("test", 0)
+	ioutil.WriteFile("current.yaml", []byte("test: 15"), 0666)
+	defer os.Remove("current.yaml")
+
+	os.Setenv("THE_TEST", "11")
+	defer os.Setenv("THE_TEST", "")
+
+	test := []string{"test-cmd", "--load", "current.yaml"}
+	set.Parse(test)
+
+	c := cli.NewContext(app, set, nil)
+
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) {
+			val := c.Int("test")
+			expect(t, val, 11)
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(cli.IntFlag{Name: "test", Value: 7, EnvVar: "THE_TEST"}),
+			cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
+	err := command.Run(c)
+
+	expect(t, err, nil)
+}

altsrc/yaml_file_loader.go

@@ -0,0 +1,84 @@
+// Disabling building of yaml support in cases where golang is 1.0 or 1.1
+// as the encoding library is not implemented or supported.
+
+// +build !go1,!go1.1
+
+package altsrc
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"os"
+
+	"github.com/codegangsta/cli"
+
+	"gopkg.in/yaml.v2"
+)
+
+type yamlSourceContext struct {
+	FilePath string
+}
+
+// NewYamlSourceFromFile creates a new Yaml InputSourceContext from a filepath.
+func NewYamlSourceFromFile(file string) (InputSourceContext, error) {
+	ymlLoader := &yamlSourceLoader{FilePath: file}
+	var results map[string]interface{}
+	err := readCommandYaml(ysl.FilePath, &results)
+	if err != nil {
+		return fmt.Errorf("Unable to load Yaml file '%s': inner error: \n'%v'", filePath, err.Error())
+	}
+
+	return &MapInputSource{valueMap: results}, nil
+}
+
+// NewYamlSourceFromFlagFunc creates a new Yaml InputSourceContext from a provided flag name and source context.
+func NewYamlSourceFromFlagFunc(flagFileName string) func(InputSourceContext, error) {
+	return func(context cli.Context) {
+		filePath := context.String(flagFileName)
+		return NewYamlSourceFromFile(filePath)
+	}
+}
+
+func readCommandYaml(filePath string, container interface{}) (err error) {
+	b, err := loadDataFrom(filePath)
+	if err != nil {
+		return err
+	}
+
+	err = yaml.Unmarshal(b, container)
+	if err != nil {
+		return err
+	}
+
+	err = nil
+	return
+}
+
+func loadDataFrom(filePath string) ([]byte, error) {
+	u, err := url.Parse(filePath)
+	if err != nil {
+		return nil, err
+	}
+
+	if u.Host != "" { // i have a host, now do i support the scheme?
+		switch u.Scheme {
+		case "http", "https":
+			res, err := http.Get(filePath)
+			if err != nil {
+				return nil, err
+			}
+			return ioutil.ReadAll(res.Body)
+		default:
+			return nil, fmt.Errorf("scheme of %s is unsupported", filePath)
+		}
+	} else if u.Path != "" { // i dont have a host, but I have a path. I am a local file.
+		if _, notFoundFileErr := os.Stat(filePath); notFoundFileErr != nil {
+			return nil, fmt.Errorf("Cannot read from file: '%s' because it does not exist.", filePath)
+		}
+		return ioutil.ReadFile(filePath)
+	} else {
+		return nil, fmt.Errorf("unable to determine how to load from path %s", filePath)
+	}
+}