altsrc: allow nested defaults in yaml files

Previously, defaults specified as nested keys in a yaml file would not
be recognized, i.e. `top: \n  bottom: key` would not be accessible using
the name `top.bottom`, but `top.bottom: key` would. These changes
support using nested keys by traversing the configuration tree if the
key name uses '.' as a delimiter.

altsrc/map_input_source.go

@@ -3,6 +3,7 @@ package altsrc
 import (
 	"fmt"
 	"reflect"
+	"strings"
 	"time"
 
 	"github.com/codegangsta/cli"
@@ -11,7 +12,31 @@ import (
 // MapInputSource implements InputSourceContext to return
 // data from the map that is loaded.
 type MapInputSource struct {
-	valueMap map[string]interface{}
+	valueMap map[interface{}]interface{}
+}
+
+// nestedVal checks if the name has '.' delimiters.
+// If so, it tries to traverse the tree by the '.' delimited sections to find
+// a nested value for the key.
+func nestedVal(name string, tree map[interface{}]interface{}) (interface{}, bool) {
+	if sections := strings.Split(name, "."); len(sections) > 1 {
+		node := tree
+		for _, section := range sections[:len(sections)-1] {
+			if child, ok := node[section]; !ok {
+				return nil, false
+			} else {
+				if ctype, ok := child.(map[interface{}]interface{}); !ok {
+					return nil, false
+				} else {
+					node = ctype
+				}
+			}
+		}
+		if val, ok := node[sections[len(sections)-1]]; ok {
+			return val, true
+		}
+	}
+	return nil, false
 }
 
 // Int returns an int from the map if it exists otherwise returns 0
@@ -22,7 +47,14 @@ func (fsm *MapInputSource) Int(name string) (int, error) {
 		if !isType {
 			return 0, incorrectTypeForFlagError(name, "int", otherGenericValue)
 		}
-
+		return otherValue, nil
+	}
+	nestedGenericValue, exists := nestedVal(name, fsm.valueMap)
+	if exists {
+		otherValue, isType := nestedGenericValue.(int)
+		if !isType {
+			return 0, incorrectTypeForFlagError(name, "int", nestedGenericValue)
+		}
 		return otherValue, nil
 	}
 
@@ -39,6 +71,14 @@ func (fsm *MapInputSource) Duration(name string) (time.Duration, error) {
 		}
 		return otherValue, nil
 	}
+	nestedGenericValue, exists := nestedVal(name, fsm.valueMap)
+	if exists {
+		otherValue, isType := nestedGenericValue.(time.Duration)
+		if !isType {
+			return 0, incorrectTypeForFlagError(name, "duration", nestedGenericValue)
+		}
+		return otherValue, nil
+	}
 
 	return 0, nil
 }
@@ -53,6 +93,14 @@ func (fsm *MapInputSource) Float64(name string) (float64, error) {
 		}
 		return otherValue, nil
 	}
+	nestedGenericValue, exists := nestedVal(name, fsm.valueMap)
+	if exists {
+		otherValue, isType := nestedGenericValue.(float64)
+		if !isType {
+			return 0, incorrectTypeForFlagError(name, "float64", nestedGenericValue)
+		}
+		return otherValue, nil
+	}
 
 	return 0, nil
 }
@@ -67,6 +115,14 @@ func (fsm *MapInputSource) String(name string) (string, error) {
 		}
 		return otherValue, nil
 	}
+	nestedGenericValue, exists := nestedVal(name, fsm.valueMap)
+	if exists {
+		otherValue, isType := nestedGenericValue.(string)
+		if !isType {
+			return "", incorrectTypeForFlagError(name, "string", nestedGenericValue)
+		}
+		return otherValue, nil
+	}
 
 	return "", nil
 }
@@ -81,6 +137,14 @@ func (fsm *MapInputSource) StringSlice(name string) ([]string, error) {
 		}
 		return otherValue, nil
 	}
+	nestedGenericValue, exists := nestedVal(name, fsm.valueMap)
+	if exists {
+		otherValue, isType := nestedGenericValue.([]string)
+		if !isType {
+			return nil, incorrectTypeForFlagError(name, "[]string", nestedGenericValue)
+		}
+		return otherValue, nil
+	}
 
 	return nil, nil
 }
@@ -95,6 +159,14 @@ func (fsm *MapInputSource) IntSlice(name string) ([]int, error) {
 		}
 		return otherValue, nil
 	}
+	nestedGenericValue, exists := nestedVal(name, fsm.valueMap)
+	if exists {
+		otherValue, isType := nestedGenericValue.([]int)
+		if !isType {
+			return nil, incorrectTypeForFlagError(name, "[]int", nestedGenericValue)
+		}
+		return otherValue, nil
+	}
 
 	return nil, nil
 }
@@ -109,6 +181,14 @@ func (fsm *MapInputSource) Generic(name string) (cli.Generic, error) {
 		}
 		return otherValue, nil
 	}
+	nestedGenericValue, exists := nestedVal(name, fsm.valueMap)
+	if exists {
+		otherValue, isType := nestedGenericValue.(cli.Generic)
+		if !isType {
+			return nil, incorrectTypeForFlagError(name, "cli.Generic", nestedGenericValue)
+		}
+		return otherValue, nil
+	}
 
 	return nil, nil
 }
@@ -123,6 +203,14 @@ func (fsm *MapInputSource) Bool(name string) (bool, error) {
 		}
 		return otherValue, nil
 	}
+	nestedGenericValue, exists := nestedVal(name, fsm.valueMap)
+	if exists {
+		otherValue, isType := nestedGenericValue.(bool)
+		if !isType {
+			return false, incorrectTypeForFlagError(name, "bool", nestedGenericValue)
+		}
+		return otherValue, nil
+	}
 
 	return false, nil
 }
@@ -137,6 +225,14 @@ func (fsm *MapInputSource) BoolT(name string) (bool, error) {
 		}
 		return otherValue, nil
 	}
+	nestedGenericValue, exists := nestedVal(name, fsm.valueMap)
+	if exists {
+		otherValue, isType := nestedGenericValue.(bool)
+		if !isType {
+			return true, incorrectTypeForFlagError(name, "bool", nestedGenericValue)
+		}
+		return otherValue, nil
+	}
 
 	return true, nil
 }