From 717d682741fa3aeb6d3ce1a670e60b3908e71444 Mon Sep 17 00:00:00 2001
From: Gustavo Bazan <gssbzn@gmail.com>
Date: Fri, 10 Jan 2020 15:35:19 +0000
Subject: [PATCH] PR comments

---
 viper.go      | 14 ++++++-------
 viper_test.go | 54 +++++++++++++++++++++++++++++++++++++++++----------
 2 files changed, 51 insertions(+), 17 deletions(-)

diff --git a/viper.go b/viper.go
index 2c7f42f..e10f239 100644
--- a/viper.go
+++ b/viper.go
@@ -1420,14 +1420,14 @@ func (v *Viper) writeConfig(filename string, force bool) error {
 	jww.INFO.Println("Attempting to write configuration to file.")
 	var configType string
 
-	if v.configType != "" {
-		configType = v.configType
-	} else {
-		ext := filepath.Ext(filename)
-		if len(ext) <= 1 {
-			return fmt.Errorf("filename: %s requires valid extension", filename)
-		}
+	ext := filepath.Ext(filename)
+	if ext != "" {
 		configType = ext[1:]
+	} else {
+		configType = v.configType
+	}
+	if configType == "" {
+		return fmt.Errorf("config type could not be determined for %s", filename)
 	}
 
 	if !stringInSlice(configType, SupportedExts) {
diff --git a/viper_test.go b/viper_test.go
index 4d35923..6c9a84a 100644
--- a/viper_test.go
+++ b/viper_test.go
@@ -1311,79 +1311,113 @@ func TestWriteConfig(t *testing.T) {
 	fs := afero.NewMemMapFs()
 	testCases := map[string]struct {
 		configName      string
-		configType      string
+		inConfigType    string
+		outConfigType   string
 		fileName        string
 		input           []byte
 		expectedContent []byte
 	}{
 		"hcl with file extension": {
 			configName:      "c",
-			configType:      "hcl",
+			inConfigType:    "hcl",
+			outConfigType:   "hcl",
 			fileName:        "c.hcl",
 			input:           hclExample,
 			expectedContent: hclWriteExpected,
 		},
 		"hcl without file extension": {
 			configName:      "c",
-			configType:      "hcl",
+			inConfigType:    "hcl",
+			outConfigType:   "hcl",
 			fileName:        "c",
 			input:           hclExample,
 			expectedContent: hclWriteExpected,
 		},
+		"hcl with file extension and mismatch type": {
+			configName:      "c",
+			inConfigType:    "hcl",
+			outConfigType:   "json",
+			fileName:        "c.hcl",
+			input:           hclExample,
+			expectedContent: hclWriteExpected,
+		},
 		"json with file extension": {
 			configName:      "c",
-			configType:      "json",
+			inConfigType:    "json",
+			outConfigType:   "json",
 			fileName:        "c.json",
 			input:           jsonExample,
 			expectedContent: jsonWriteExpected,
 		},
 		"json without file extension": {
 			configName:      "c",
-			configType:      "json",
+			inConfigType:    "json",
+			outConfigType:   "json",
 			fileName:        "c",
 			input:           jsonExample,
 			expectedContent: jsonWriteExpected,
 		},
+		"json with file extension and mismatch type": {
+			configName:      "c",
+			inConfigType:    "json",
+			outConfigType:   "hcl",
+			fileName:        "c.json",
+			input:           jsonExample,
+			expectedContent: jsonWriteExpected,
+		},
 		"properties with file extension": {
 			configName:      "c",
-			configType:      "properties",
+			inConfigType:    "properties",
+			outConfigType:   "properties",
 			fileName:        "c.properties",
 			input:           propertiesExample,
 			expectedContent: propertiesWriteExpected,
 		},
 		"properties without file extension": {
 			configName:      "c",
-			configType:      "properties",
+			inConfigType:    "properties",
+			outConfigType:   "properties",
 			fileName:        "c",
 			input:           propertiesExample,
 			expectedContent: propertiesWriteExpected,
 		},
 		"yaml with file extension": {
 			configName:      "c",
-			configType:      "yaml",
+			inConfigType:    "yaml",
+			outConfigType:   "yaml",
 			fileName:        "c.yaml",
 			input:           yamlExample,
 			expectedContent: yamlWriteExpected,
 		},
 		"yaml without file extension": {
 			configName:      "c",
-			configType:      "yaml",
+			inConfigType:    "yaml",
+			outConfigType:   "yaml",
 			fileName:        "c",
 			input:           yamlExample,
 			expectedContent: yamlWriteExpected,
 		},
+		"yaml with file extension and mismatch type": {
+			configName:      "c",
+			inConfigType:    "yaml",
+			outConfigType:   "json",
+			fileName:        "c.yaml",
+			input:           yamlExample,
+			expectedContent: yamlWriteExpected,
+		},
 	}
 	for name, tc := range testCases {
 		t.Run(name, func(t *testing.T) {
 			v := New()
 			v.SetFs(fs)
 			v.SetConfigName(tc.fileName)
-			v.SetConfigType(tc.configType)
+			v.SetConfigType(tc.inConfigType)
 
 			err := v.ReadConfig(bytes.NewBuffer(tc.input))
 			if err != nil {
 				t.Fatal(err)
 			}
+			v.SetConfigType(tc.outConfigType)
 			if err := v.WriteConfigAs(tc.fileName); err != nil {
 				t.Fatal(err)
 			}