Detect input format based on file name extension (#1582)

* detect inputFormat from filename

* refactor and extract func InputFormatFromFilename

* detect inputFormat only when file is provided

* add test for automatic input format detection

cmd/constant.go

@@ -7,7 +7,8 @@ var unwrapScalar = false
 var writeInplace = false
 var outputToJSON = false
 var outputFormat = "yaml"
-var inputFormat = "yaml"
+var inputFormatDefault = "yaml"
+var inputFormat = ""
 
 var exitStatus = false
 var forceColor = false

cmd/evaluate_all_command.go

@@ -75,7 +75,12 @@ func evaluateAll(cmd *cobra.Command, args []string) (cmdError error) {
 		return err
 	}
 
-	decoder, err := configureDecoder(true)
+	inputFilename := ""
+	if len(args) > 0 {
+		inputFilename = args[0]
+	}
+
+	decoder, err := configureDecoder(true, inputFilename)
 	if err != nil {
 		return err
 	}

cmd/evalute_sequence_command.go

@@ -100,7 +100,12 @@ func evaluateSequence(cmd *cobra.Command, args []string) (cmdError error) {
 
 	printer := yqlib.NewPrinter(encoder, printerWriter)
 
-	decoder, err := configureDecoder(false)
+	inputFilename := ""
+	if len(args) > 0 {
+		inputFilename = args[0]
+	}
+
+	decoder, err := configureDecoder(false, inputFilename)
 	if err != nil {
 		return err
 	}

cmd/root.go

@@ -85,7 +85,7 @@ yq -P sample.json
 	}
 
 	rootCmd.PersistentFlags().StringVarP(&outputFormat, "output-format", "o", "yaml", "[yaml|y|json|j|props|p|xml|x] output format type.")
-	rootCmd.PersistentFlags().StringVarP(&inputFormat, "input-format", "p", "yaml", "[yaml|y|props|p|xml|x] parse format for input. Note that json is a subset of yaml.")
+	rootCmd.PersistentFlags().StringVarP(&inputFormat, "input-format", "p", "", "[yaml|y|props|p|xml|x] parse format for input. Note that json is a subset of yaml.")
 
 	rootCmd.PersistentFlags().StringVar(&yqlib.ConfiguredXMLPreferences.AttributePrefix, "xml-attribute-prefix", yqlib.ConfiguredXMLPreferences.AttributePrefix, "prefix for xml attributes")
 	rootCmd.PersistentFlags().StringVar(&yqlib.ConfiguredXMLPreferences.ContentName, "xml-content-name", yqlib.ConfiguredXMLPreferences.ContentName, "name for xml content (if no attribute name is present).")

cmd/utils.go

@@ -56,7 +56,12 @@ func initCommand(cmd *cobra.Command, args []string) (string, []string, error) {
 	return expression, args, nil
 }
 
-func configureDecoder(evaluateTogether bool) (yqlib.Decoder, error) {
+func configureDecoder(evaluateTogether bool, inputFilename string) (yqlib.Decoder, error) {
+	if inputFormat == "" {
+		inputFormat = yqlib.InputFormatFromFilename(inputFilename, inputFormatDefault)
+	} else {
+		yqlib.GetLogger().Debugf("user specified inputFormat '%s'", inputFormat)
+	}
 	yqlibInputFormat, err := yqlib.InputFormatFromString(inputFormat)
 	if err != nil {
 		return nil, err