Fix altsrc slice inputs so that they correctly parse

Was previously attempting to cast directly from []interface{} to
[]string or []int which Go doesn't support. Instead, we iterate over and
cast each value (error'ing if the value is not the correct format).

Fixes #580

altsrc/flag_test.go

@@ -59,7 +59,7 @@ func TestStringSliceApplyInputSourceValue(t *testing.T) {
 	c := runTest(t, testApplyInputSource{
 		Flag:     NewStringSliceFlag(cli.StringSliceFlag{Name: "test"}),
 		FlagName: "test",
-		MapValue: []string{"hello", "world"},
+		MapValue: []interface{}{"hello", "world"},
 	})
 	expect(t, c.StringSlice("test"), []string{"hello", "world"})
 }
@@ -68,7 +68,7 @@ func TestStringSliceApplyInputSourceMethodContextSet(t *testing.T) {
 	c := runTest(t, testApplyInputSource{
 		Flag:               NewStringSliceFlag(cli.StringSliceFlag{Name: "test"}),
 		FlagName:           "test",
-		MapValue:           []string{"hello", "world"},
+		MapValue:           []interface{}{"hello", "world"},
 		ContextValueString: "ohno",
 	})
 	expect(t, c.StringSlice("test"), []string{"ohno"})
@@ -78,7 +78,7 @@ func TestStringSliceApplyInputSourceMethodEnvVarSet(t *testing.T) {
 	c := runTest(t, testApplyInputSource{
 		Flag:        NewStringSliceFlag(cli.StringSliceFlag{Name: "test", EnvVar: "TEST"}),
 		FlagName:    "test",
-		MapValue:    []string{"hello", "world"},
+		MapValue:    []interface{}{"hello", "world"},
 		EnvVarName:  "TEST",
 		EnvVarValue: "oh,no",
 	})
@@ -89,7 +89,7 @@ func TestIntSliceApplyInputSourceValue(t *testing.T) {
 	c := runTest(t, testApplyInputSource{
 		Flag:     NewIntSliceFlag(cli.IntSliceFlag{Name: "test"}),
 		FlagName: "test",
-		MapValue: []int{1, 2},
+		MapValue: []interface{}{1, 2},
 	})
 	expect(t, c.IntSlice("test"), []int{1, 2})
 }
@@ -98,7 +98,7 @@ func TestIntSliceApplyInputSourceMethodContextSet(t *testing.T) {
 	c := runTest(t, testApplyInputSource{
 		Flag:               NewIntSliceFlag(cli.IntSliceFlag{Name: "test"}),
 		FlagName:           "test",
-		MapValue:           []int{1, 2},
+		MapValue:           []interface{}{1, 2},
 		ContextValueString: "3",
 	})
 	expect(t, c.IntSlice("test"), []int{3})
@@ -108,7 +108,7 @@ func TestIntSliceApplyInputSourceMethodEnvVarSet(t *testing.T) {
 	c := runTest(t, testApplyInputSource{
 		Flag:        NewIntSliceFlag(cli.IntSliceFlag{Name: "test", EnvVar: "TEST"}),
 		FlagName:    "test",
-		MapValue:    []int{1, 2},
+		MapValue:    []interface{}{1, 2},
 		EnvVarName:  "TEST",
 		EnvVarValue: "3,4",
 	})

altsrc/map_input_source.go

@@ -130,45 +130,59 @@ func (fsm *MapInputSource) String(name string) (string, error) {
 // 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 {
+	if !exists {
-		otherValue, isType := otherGenericValue.([]string)
+		otherGenericValue, exists = nestedVal(name, fsm.valueMap)
-		if !isType {
+		if !exists {
-			return nil, incorrectTypeForFlagError(name, "[]string", otherGenericValue)
+			return nil, nil
 		}
-		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
+	otherValue, isType := otherGenericValue.([]interface{})
+	if !isType {
+		return nil, incorrectTypeForFlagError(name, "[]interface{}", otherGenericValue)
+	}
+
+	var stringSlice = make([]string, 0, len(otherValue))
+	for i, v := range otherValue {
+		stringValue, isType := v.(string)
+
+		if !isType {
+			return nil, incorrectTypeForFlagError(fmt.Sprintf("%s[%d]", name, i), "string", v)
+		}
+
+		stringSlice = append(stringSlice, stringValue)
+	}
+
+	return stringSlice, 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 {
+	if !exists {
-		otherValue, isType := otherGenericValue.([]int)
+		otherGenericValue, exists = nestedVal(name, fsm.valueMap)
-		if !isType {
+		if !exists {
-			return nil, incorrectTypeForFlagError(name, "[]int", otherGenericValue)
+			return nil, nil
 		}
-		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
+	otherValue, isType := otherGenericValue.([]interface{})
+	if !isType {
+		return nil, incorrectTypeForFlagError(name, "[]interface{}", otherGenericValue)
+	}
+
+	var intSlice = make([]int, 0, len(otherValue))
+	for i, v := range otherValue {
+		intValue, isType := v.(int)
+
+		if !isType {
+			return nil, incorrectTypeForFlagError(fmt.Sprintf("%s[%d]", name, i), "int", v)
+		}
+
+		intSlice = append(intSlice, intValue)
+	}
+
+	return intSlice, nil
 }
 
 // Generic returns an cli.Generic from the map if it exists otherwise returns nil