Update to add build contraints to not compile in yaml support

in the case the golang version is less than golang 1.2

README.md

@@ -28,7 +28,7 @@ export PATH=$PATH:$GOPATH/bin
 
 ## Getting Started
 
-One of the philosophies behind `cli.go` is that an API should be playful and full of discovery. So a `cli.go` app can be as little as one line of code in `main()`. 
+One of the philosophies behind `cli.go` is that an API should be playful and full of discovery. So a `cli.go` app can be as little as one line of code in `main()`.
 
 ``` go
 package main
@@ -60,7 +60,7 @@ func main() {
   app.Action = func(c *cli.Context) {
     println("boom! I say!")
   }
-  
+
   app.Run(os.Args)
 }
 ```
@@ -238,6 +238,48 @@ app.Flags = []cli.Flag {
 }
 ```
 
+#### Values from alternate input sources (YAML and others)
+
+There is a separate package altsrc that adds support for getting flag values from other input sources like YAML.
+
+In order to get values for a flag from an alternate input source the following code would be added to wrap an existing cli.Flag like below:
+
+``` go
+  altsrc.NewIntFlag(cli.IntFlag{Name: "test"})
+```
+
+Initialization must also occur for these flags. Below is an example initializing getting data from a yaml file below.
+
+``` go
+  command.Before = altsrc.InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
+```
+
+The code above will use the "load" string as a flag name to get the file name of a yaml file from the cli.Context. 
+It will then use that file name to initialize the yaml input source for any flags that are defined on that command. 
+As a note the "load" flag used would also have to be defined on the command flags in order for this code snipped to work.
+
+Currently only YAML files are supported but developers can add support for other input sources by implementing the
+altsrc.InputSourceContext for their given sources.
+
+Here is a more complete sample of a command using YAML support:
+
+``` go
+	command := &cli.Command{
+		Name:        "test-cmd",
+		Aliases:     []string{"tc"},
+		Usage:       "this is for testing",
+		Description: "testing",
+		Action: func(c *cli.Context) {
+			// Action to run
+		},
+		Flags: []cli.Flag{
+			NewIntFlag(cli.IntFlag{Name: "test"}),
+			cli.StringFlag{Name: "load"}},
+	}
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
+	err := command.Run(c)
+```
+
 ### Subcommands
 
 Subcommands can be defined for a more git-like command line app.

altsrc/flag.go

@@ -1,4 +1,4 @@
-package inputfilesupport
+package altsrc
 
 import (
 	"flag"
@@ -14,7 +14,53 @@ import (
 // allows a value to be set on the existing parsed flags.
 type FlagInputSourceExtension interface {
 	cli.Flag
-	ApplyInputSourceValue(context *cli.Context, isc InputSourceContext)
+	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
@@ -30,10 +76,13 @@ func NewGenericFlag(flag cli.GenericFlag) *GenericFlag {
 }
 
 // ApplyInputSourceValue applies a generic value to the flagSet if required
-func (f *GenericFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) {
+func (f *GenericFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
 	if f.set != nil {
 		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
-			value := isc.Generic(f.GenericFlag.Name)
+			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())
@@ -41,6 +90,8 @@ func (f *GenericFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourc
 			}
 		}
 	}
+
+	return nil
 }
 
 // Apply saves the flagSet for later usage then calls
@@ -63,10 +114,13 @@ func NewStringSliceFlag(flag cli.StringSliceFlag) *StringSliceFlag {
 }
 
 // ApplyInputSourceValue applies a StringSlice value to the flagSet if required
-func (f *StringSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) {
+func (f *StringSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
 	if f.set != nil {
 		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
-			value := isc.StringSlice(f.StringSliceFlag.Name)
+			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) {
@@ -78,6 +132,7 @@ func (f *StringSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputS
 			}
 		}
 	}
+	return nil
 }
 
 // Apply saves the flagSet for later usage then calls
@@ -100,10 +155,13 @@ func NewIntSliceFlag(flag cli.IntSliceFlag) *IntSliceFlag {
 }
 
 // ApplyInputSourceValue applies a IntSlice value if required
-func (f *IntSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) {
+func (f *IntSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
 	if f.set != nil {
 		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
-			value := isc.IntSlice(f.IntSliceFlag.Name)
+			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) {
@@ -115,6 +173,7 @@ func (f *IntSliceFlag) ApplyInputSourceValue(context *cli.Context, isc InputSour
 			}
 		}
 	}
+	return nil
 }
 
 // Apply saves the flagSet for later usage then calls
@@ -137,10 +196,13 @@ func NewBoolFlag(flag cli.BoolFlag) *BoolFlag {
 }
 
 // ApplyInputSourceValue applies a Bool value to the flagSet if required
-func (f *BoolFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) {
+func (f *BoolFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
 	if f.set != nil {
 		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
-			value := isc.Bool(f.BoolFlag.Name)
+			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))
@@ -148,6 +210,7 @@ func (f *BoolFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceCo
 			}
 		}
 	}
+	return nil
 }
 
 // Apply saves the flagSet for later usage then calls
@@ -170,10 +233,13 @@ func NewBoolTFlag(flag cli.BoolTFlag) *BoolTFlag {
 }
 
 // ApplyInputSourceValue applies a BoolT value to the flagSet if required
-func (f *BoolTFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) {
+func (f *BoolTFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
 	if f.set != nil {
 		if !context.IsSet(f.Name) && !isEnvVarSet(f.EnvVar) {
-			value := isc.BoolT(f.BoolTFlag.Name)
+			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))
@@ -181,6 +247,7 @@ func (f *BoolTFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceC
 			}
 		}
 	}
+	return nil
 }
 
 // Apply saves the flagSet for later usage then calls
@@ -204,10 +271,13 @@ func NewStringFlag(flag cli.StringFlag) *StringFlag {
 }
 
 // ApplyInputSourceValue applies a String value to the flagSet if required
-func (f *StringFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) {
+func (f *StringFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
 	if f.set != nil {
 		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVar)) {
-			value := isc.String(f.StringFlag.Name)
+			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)
@@ -215,6 +285,7 @@ func (f *StringFlag) ApplyInputSourceValue(context *cli.Context, isc InputSource
 			}
 		}
 	}
+	return nil
 }
 
 // Apply saves the flagSet for later usage then calls
@@ -238,10 +309,13 @@ func NewIntFlag(flag cli.IntFlag) *IntFlag {
 }
 
 // ApplyInputSourceValue applies a int value to the flagSet if required
-func (f *IntFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) {
+func (f *IntFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
 	if f.set != nil {
 		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVar)) {
-			value := isc.Int(f.IntFlag.Name)
+			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))
@@ -249,6 +323,7 @@ func (f *IntFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceCon
 			}
 		}
 	}
+	return nil
 }
 
 // Apply saves the flagSet for later usage then calls
@@ -271,10 +346,13 @@ func NewDurationFlag(flag cli.DurationFlag) *DurationFlag {
 }
 
 // ApplyInputSourceValue applies a Duration value to the flagSet if required
-func (f *DurationFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) {
+func (f *DurationFlag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
 	if f.set != nil {
 		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVar)) {
-			value := isc.Duration(f.DurationFlag.Name)
+			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())
@@ -282,6 +360,7 @@ func (f *DurationFlag) ApplyInputSourceValue(context *cli.Context, isc InputSour
 			}
 		}
 	}
+	return nil
 }
 
 // Apply saves the flagSet for later usage then calls
@@ -305,10 +384,13 @@ func NewFloat64Flag(flag cli.Float64Flag) *Float64Flag {
 }
 
 // ApplyInputSourceValue applies a Float64 value to the flagSet if required
-func (f *Float64Flag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) {
+func (f *Float64Flag) ApplyInputSourceValue(context *cli.Context, isc InputSourceContext) error {
 	if f.set != nil {
 		if !(context.IsSet(f.Name) || isEnvVarSet(f.EnvVar)) {
-			value := isc.Float64(f.Float64Flag.Name)
+			value, err := isc.Float64(f.Float64Flag.Name)
+			if err != nil {
+				return err
+			}
 			if value > 0 {
 				floatStr := float64ToString(value)
 				eachName(f.Name, func(name string) {
@@ -317,6 +399,7 @@ func (f *Float64Flag) ApplyInputSourceValue(context *cli.Context, isc InputSourc
 			}
 		}
 	}
+	return nil
 }
 
 // Apply saves the flagSet for later usage then calls

altsrc/flag_test.go

@@ -1,4 +1,4 @@
-package inputfilesupport
+package altsrc
 
 import (
 	"flag"

altsrc/helpers_test.go

@@ -1,4 +1,4 @@
-package inputfilesupport
+package altsrc
 
 import (
 	"reflect"

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

@@ -1,4 +1,9 @@
-package inputfilesupport
+// 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"
@@ -32,7 +37,7 @@ func TestCommandYamlFileTest(t *testing.T) {
 			NewIntFlag(cli.IntFlag{Name: "test"}),
 			cli.StringFlag{Name: "load"}},
 	}
-	command.Before = InitializeYaml("load", command.Flags)
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
 	err := command.Run(c)
 
 	expect(t, err, nil)
@@ -64,7 +69,7 @@ func TestCommandYamlFileTestGlobalEnvVarWins(t *testing.T) {
 			NewIntFlag(cli.IntFlag{Name: "test", EnvVar: "THE_TEST"}),
 			cli.StringFlag{Name: "load"}},
 	}
-	command.Before = InitializeYaml("load", command.Flags)
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
 
 	err := command.Run(c)
 
@@ -95,7 +100,7 @@ func TestCommandYamlFileTestSpecifiedFlagWins(t *testing.T) {
 			NewIntFlag(cli.IntFlag{Name: "test"}),
 			cli.StringFlag{Name: "load"}},
 	}
-	command.Before = InitializeYaml("load", command.Flags)
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
 
 	err := command.Run(c)
 
@@ -126,7 +131,7 @@ func TestCommandYamlFileTestDefaultValueFileWins(t *testing.T) {
 			NewIntFlag(cli.IntFlag{Name: "test", Value: 7}),
 			cli.StringFlag{Name: "load"}},
 	}
-	command.Before = InitializeYaml("load", command.Flags)
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
 
 	err := command.Run(c)
 
@@ -160,7 +165,7 @@ func TestCommandYamlFileFlagHasDefaultGlobalEnvYamlSetGlobalEnvWins(t *testing.T
 			NewIntFlag(cli.IntFlag{Name: "test", Value: 7, EnvVar: "THE_TEST"}),
 			cli.StringFlag{Name: "load"}},
 	}
-	command.Before = InitializeYaml("load", command.Flags)
+	command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
 	err := command.Run(c)
 
 	expect(t, err, nil)

altsrc/yaml_file_loader.go

@@ -1,4 +1,9 @@
-package inputfilesupport
+// 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"
@@ -8,54 +13,34 @@ import (
 	"os"
 
 	"github.com/codegangsta/cli"
+
 	"gopkg.in/yaml.v2"
 )
 
-// LoadFlag is a default load flag used to get a inputFilePath for a yaml file
-var LoadFlag = cli.StringFlag{
-	Name:  "load",
-	Usage: "file path to a yaml file",
-}
-
-// InitializeYaml is used to initialize Before funcs for commands.
-func InitializeYaml(filePathFlagName string, flags []cli.Flag) func(context *cli.Context) error {
-	return func(context *cli.Context) error {
-		filePath := context.String(filePathFlagName)
-		ymlLoader := &YamlSourceLoader{FilePath: filePath}
-		yamlInputSource, err := ymlLoader.Load()
-		if err != nil {
-			return fmt.Errorf("Unable to load Yaml file '%s': inner error: \n'%v'", filePath, err.Error())
-		}
-
-		for _, f := range flags {
-			inputSourceExtendedFlag, isType := f.(FlagInputSourceExtension)
-			if isType {
-				inputSourceExtendedFlag.ApplyInputSourceValue(context, yamlInputSource)
-			}
-		}
-
-		return nil
-	}
-}
-
-// YamlSourceLoader can load yaml files and return a InputSourceContext
-// to be used for a parameter value
-type YamlSourceLoader struct {
+type yamlSourceContext struct {
 	FilePath string
 }
 
-// Load returns an input source if successful or an error if there is a failure
-// loading the yaml file
-func (ysl *YamlSourceLoader) Load() (InputSourceContext, error) {
+// 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 nil, err
+		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 {

inputfilesupport/input_source_context.go

@@ -1,21 +0,0 @@
-package inputfilesupport
-
-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
-	Duration(name string) time.Duration
-	Float64(name string) float64
-	String(name string) string
-	StringSlice(name string) []string
-	IntSlice(name string) []int
-	Generic(name string) cli.Generic
-	Bool(name string) bool
-	BoolT(name string) bool
-}

inputfilesupport/map_input_source.go

@@ -1,132 +0,0 @@
-package inputfilesupport
-
-import (
-	"time"
-
-	"github.com/codegangsta/cli"
-)
-
-// MapInputSource implements InputSourceContext to return
-// data from the map that is loaded.
-// TODO: Didn't implement a way to write out various errors
-// need to figure this part out.
-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 {
-	otherGenericValue, exists := fsm.valueMap[name]
-	if exists {
-		otherValue, isType := otherGenericValue.(int)
-		if isType {
-			return otherValue
-		}
-	}
-
-	return 0
-}
-
-// Duration returns a duration from the map if it exists otherwise returns 0
-func (fsm *MapInputSource) Duration(name string) time.Duration {
-	otherGenericValue, exists := fsm.valueMap[name]
-	if exists {
-		otherValue, isType := otherGenericValue.(time.Duration)
-		if isType {
-			return otherValue
-		}
-	}
-
-	return 0
-}
-
-// Float64 returns an float64 from the map if it exists otherwise returns 0
-func (fsm *MapInputSource) Float64(name string) float64 {
-	otherGenericValue, exists := fsm.valueMap[name]
-	if exists {
-		otherValue, isType := otherGenericValue.(float64)
-		if isType {
-			return otherValue
-		}
-	}
-
-	return 0
-}
-
-// String returns a string from the map if it exists otherwise returns an empty string
-func (fsm *MapInputSource) String(name string) string {
-	otherGenericValue, exists := fsm.valueMap[name]
-	if exists {
-		otherValue, isType := otherGenericValue.(string)
-		if isType {
-			return otherValue
-		}
-	}
-
-	return ""
-}
-
-// StringSlice returns an []string from the map if it exists otherwise returns nil
-func (fsm *MapInputSource) StringSlice(name string) []string {
-	otherGenericValue, exists := fsm.valueMap[name]
-	if exists {
-		otherValue, isType := otherGenericValue.([]string)
-		if isType {
-			return otherValue
-		}
-	}
-
-	return nil
-}
-
-// IntSlice returns an []int from the map if it exists otherwise returns nil
-func (fsm *MapInputSource) IntSlice(name string) []int {
-	otherGenericValue, exists := fsm.valueMap[name]
-	if exists {
-		otherValue, isType := otherGenericValue.([]int)
-		if isType {
-			return otherValue
-		}
-	}
-
-	return nil
-}
-
-// Generic returns an cli.Generic from the map if it exists otherwise returns nil
-func (fsm *MapInputSource) Generic(name string) cli.Generic {
-	otherGenericValue, exists := fsm.valueMap[name]
-	if exists {
-		otherValue, isType := otherGenericValue.(cli.Generic)
-		if isType {
-			return otherValue
-		}
-	}
-
-	return nil
-}
-
-// Bool returns an bool from the map otherwise returns false
-func (fsm *MapInputSource) Bool(name string) bool {
-	otherGenericValue, exists := fsm.valueMap[name]
-	if exists {
-		otherValue, isType := otherGenericValue.(bool)
-		if isType {
-			return otherValue
-		}
-	}
-
-	return false
-}
-
-// BoolT returns an bool from the map otherwise returns true
-func (fsm *MapInputSource) BoolT(name string) bool {
-	otherGenericValue, exists := fsm.valueMap[name]
-	if exists {
-		otherValue, isType := otherGenericValue.(bool)
-		if isType {
-			return otherValue
-		}
-	}
-
-	return true
-}