Add `--nul-output|-0` flag to separate element with NUL character (#1550)

This is to ensure solid parsing of complex data (with any binary
content except NUL chars) by separating the `yq` root collection
member's output with NUL char. As a safe-guard, an error will be cast
if trying to use NUL character with content that contains itself NUL
characters inside.

cmd/constant.go

@@ -18,6 +18,7 @@ var colorsEnabled = false
 var indent = 2
 var noDocSeparators = false
 var nullInput = false
+var nulSepOutput = false
 var verbose = false
 var version = false
 var prettyPrint = false

cmd/evaluate_all_command.go

@@ -90,6 +90,9 @@ func evaluateAll(cmd *cobra.Command, args []string) (cmdError error) {
 	}
 
 	printer := yqlib.NewPrinter(encoder, printerWriter)
+	if nulSepOutput {
+		printer.SetNulSepOutput(true)
+	}
 
 	if frontMatter != "" {
 		frontMatterHandler := yqlib.NewFrontMatterHandler(args[0])

cmd/evalute_sequence_command.go

@@ -99,6 +99,9 @@ func evaluateSequence(cmd *cobra.Command, args []string) (cmdError error) {
 	}
 
 	printer := yqlib.NewPrinter(encoder, printerWriter)
+	if nulSepOutput {
+		printer.SetNulSepOutput(true)
+	}
 
 	decoder, err := configureDecoder(false)
 	if err != nil {

cmd/root.go

@@ -86,6 +86,7 @@ yq -P sample.json
 	rootCmd.PersistentFlags().BoolVarP(&writeInplace, "inplace", "i", false, "update the file inplace of first file given.")
 	rootCmd.PersistentFlags().VarP(unwrapScalarFlag, "unwrapScalar", "r", "unwrap scalar, print the value with no quotes, colors or comments. Defaults to true for yaml")
 	rootCmd.PersistentFlags().Lookup("unwrapScalar").NoOptDefVal = "true"
+	rootCmd.PersistentFlags().BoolVarP(&nulSepOutput, "nul-output", "0", false, "Use NUL char to separate values. If unwrap scalar is also set, fail if unwrapped scalar contains NUL char.")
 
 	rootCmd.PersistentFlags().BoolVarP(&prettyPrint, "prettyPrint", "P", false, "pretty print, shorthand for '... style = \"\"'")
 	rootCmd.PersistentFlags().BoolVarP(&exitStatus, "exit-status", "e", false, "set exit status if there are no matches or null or false is returned")