Automatically add "-" when piping and its missing

cmd/utils.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/mikefarah/yq/v4/pkg/yqlib"
 	"github.com/spf13/cobra"
+	"gopkg.in/op/go-logging.v1"
 )
 
 func initCommand(cmd *cobra.Command, args []string) (firstFileIndex int, err error) {
@@ -98,6 +99,33 @@ func configureEncoder(format yqlib.PrinterOutputFormat) yqlib.Encoder {
 // without this - yq detects there is stdin (thanks githubactions),
 // then tries to parse the filename as an expression
 func maybeFile(str string) bool {
+	yqlib.GetLogger().Debugf("checking '%v' is a file", str)
 	stat, err := os.Stat(str) // #nosec
-	return err == nil && !stat.IsDir()
+	result := err == nil && !stat.IsDir()
+	if yqlib.GetLogger().IsEnabledFor(logging.DEBUG) {
+		if err != nil {
+			yqlib.GetLogger().Debugf("error: %v", err)
+		} else {
+			yqlib.GetLogger().Debugf("error: %v, dir: %v", err, stat.IsDir())
+		}
+		yqlib.GetLogger().Debugf("result: %v", result)
+	}
+	return result
+}
+
+func processArgs(pipingStdin bool, args []string) []string {
+	if !pipingStdin {
+		return args
+	}
+
+	for _, arg := range args {
+		if arg == "-" {
+			return args
+		}
+	}
+	yqlib.GetLogger().Debugf("missing '-', adding it to the end")
+
+	// we're piping from stdin, but there's no '-' arg
+	// lets add one to the end
+	return append(args, "-")
 }