From 3e83ff7ac866d0bf63c7cd9fa2cddf22dbdddf97 Mon Sep 17 00:00:00 2001
From: Ryan SIU <ryan.siu@cloverhealth.com>
Date: Fri, 10 Jan 2020 16:34:31 +0800
Subject: [PATCH] #20 Read the top level keys only

---
 test/fixture/keyonly.yaml |  6 ++++++
 yq.go                     |  9 +++++++++
 yq_test.go                | 26 ++++++++++++++++++++++++++
 3 files changed, 41 insertions(+)
 create mode 100644 test/fixture/keyonly.yaml

diff --git a/test/fixture/keyonly.yaml b/test/fixture/keyonly.yaml
new file mode 100644
index 00000000..f2dd3309
--- /dev/null
+++ b/test/fixture/keyonly.yaml
@@ -0,0 +1,6 @@
+a:
+  b:
+    c: 1
+  d:
+    e: 2
+  f:
diff --git a/yq.go b/yq.go
index d24d44c0..31154110 100644
--- a/yq.go
+++ b/yq.go
@@ -25,6 +25,7 @@ var writeInplace = false
 var writeScript = ""
 var outputToJSON = false
 var overwriteFlag = false
+var keyOnlyFlag = false
 var allowEmptyFlag = false
 var appendFlag = false
 var verbose = false
@@ -111,6 +112,7 @@ yq r -- things.yaml --key-starting-with-dashes
 	}
 	cmdRead.PersistentFlags().StringVarP(&docIndex, "doc", "d", "0", "process document index number (0 based, * for all documents)")
 	cmdRead.PersistentFlags().BoolVarP(&outputToJSON, "tojson", "j", false, "output as json")
+	cmdRead.PersistentFlags().BoolVarP(&keyOnlyFlag, "keyonly", "k", false, "output with top level keys only")
 	return cmdRead
 }
 
@@ -304,6 +306,13 @@ func readProperty(cmd *cobra.Command, args []string) error {
 		dataBucket = mappedDocs
 	}
 
+	if keyOnlyFlag {
+		for _, value := range dataBucket.(yaml.MapSlice) {
+			cmd.Println(value.Key)
+		}
+		return nil
+	}
+
 	dataStr, err := toString(dataBucket)
 	if err != nil {
 		return err
diff --git a/yq_test.go b/yq_test.go
index 677f7bd0..05c78a94 100644
--- a/yq_test.go
+++ b/yq_test.go
@@ -1,12 +1,14 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"runtime"
 	"testing"
 
 	"github.com/mikefarah/yq/v2/pkg/marshal"
 	"github.com/mikefarah/yq/v2/test"
+	"github.com/spf13/cobra"
 )
 
 func TestMultilineString(t *testing.T) {
@@ -58,3 +60,27 @@ func TestNewYaml_WithUnknownScript(t *testing.T) {
 	}
 	test.AssertResult(t, expectedOutput, err.Error())
 }
+
+func TestReadWithKeyOnly(t *testing.T) {
+	readCmd := createReadCmd()
+	expectedResult := `b
+d
+f
+`
+	actualResult, err := executeTestCommand(readCmd, "test/fixture/keyonly.yaml", "a", "-k")
+	if err != nil {
+		t.Error(err.Error())
+	}
+	test.AssertResult(t, expectedResult, actualResult)
+}
+
+func executeTestCommand(command *cobra.Command, args ...string) (output string, err error) {
+	buf := new(bytes.Buffer)
+
+	command.SetOutput(buf)
+	command.SetArgs(args)
+
+	_, err = command.ExecuteC()
+
+	return buf.String(), err
+}