From 699fce9da43f674afeebd5ea162a17fecd60ba4d Mon Sep 17 00:00:00 2001
From: Mike Farah <mikefarah@gmail.com>
Date: Mon, 3 Feb 2020 10:13:48 +1100
Subject: [PATCH] Added default value flag - for printing out a value when
 reading and there are no matches

---
 cmd/commands_test.go | 14 ++++++++++++++
 cmd/constant.go      |  1 +
 cmd/read.go          |  1 +
 cmd/utils.go         |  3 +++
 4 files changed, 19 insertions(+)

diff --git a/cmd/commands_test.go b/cmd/commands_test.go
index 7be6ebf4..f74d677e 100644
--- a/cmd/commands_test.go
+++ b/cmd/commands_test.go
@@ -356,6 +356,20 @@ func TestReadEmptyContentCmd(t *testing.T) {
 	test.AssertResult(t, expectedOutput, result.Output)
 }
 
+func TestReadEmptyContentWithDefaultValueCmd(t *testing.T) {
+	content := ``
+	filename := test.WriteTempYamlFile(content)
+	defer test.RemoveTempYamlFile(filename)
+
+	cmd := getRootCommand()
+	result := test.RunCmd(cmd, fmt.Sprintf("read --defaultValue things %s", filename))
+	if result.Error != nil {
+		t.Error(result.Error)
+	}
+	expectedOutput := `things`
+	test.AssertResult(t, expectedOutput, result.Output)
+}
+
 func TestReadPrettyPrintCmd(t *testing.T) {
 	cmd := getRootCommand()
 	result := test.RunCmd(cmd, "read -P ../examples/sample.json")
diff --git a/cmd/constant.go b/cmd/constant.go
index 476987d7..49043371 100644
--- a/cmd/constant.go
+++ b/cmd/constant.go
@@ -11,6 +11,7 @@ var writeInplace = false
 var writeScript = ""
 var outputToJSON = false
 var prettyPrint = false
+var defaultValue = ""
 var overwriteFlag = false
 var autoCreateFlag = true
 var allowEmptyFlag = false
diff --git a/cmd/read.go b/cmd/read.go
index 4c22937e..f8a392e6 100644
--- a/cmd/read.go
+++ b/cmd/read.go
@@ -26,6 +26,7 @@ yq r -- things.yaml '--key-starting-with-dashes.blah'
 	cmdRead.PersistentFlags().StringVarP(&docIndex, "doc", "d", "0", "process document index number (0 based, * for all documents)")
 	cmdRead.PersistentFlags().StringVarP(&printMode, "printMode", "p", "v", "print mode (v (values, default), p (paths), pv (path and value pairs)")
 	cmdRead.PersistentFlags().BoolVarP(&prettyPrint, "prettyPrint", "P", false, "pretty print (does not have an affect with json output)")
+	cmdRead.PersistentFlags().StringVarP(&defaultValue, "defaultValue", "D", "", "default value printed when there are no results")
 	return cmdRead
 }
 
diff --git a/cmd/utils.go b/cmd/utils.go
index aa6de02f..878f0dee 100644
--- a/cmd/utils.go
+++ b/cmd/utils.go
@@ -104,6 +104,9 @@ func updateStyleOfNode(node *yaml.Node, style yaml.Style) {
 func printResults(matchingNodes []*yqlib.NodeContext, cmd *cobra.Command) error {
 	if len(matchingNodes) == 0 {
 		log.Debug("no matching results, nothing to print")
+		if defaultValue != "" {
+			cmd.Print(defaultValue)
+		}
 		return nil
 	}