From c7ae247183cb70a9401b21f8a0804634c3f15cb6 Mon Sep 17 00:00:00 2001
From: "Deomid \"rojer\" Ryabkov" <rojer9@fb.com>
Date: Wed, 10 Mar 2021 17:56:13 +0000
Subject: [PATCH] Omit unset fields of Target when serializing JSON

---
 pkg/target/target.go      | 15 ++++++++-------
 pkg/target/target_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/pkg/target/target.go b/pkg/target/target.go
index eea38a26..b84a725b 100644
--- a/pkg/target/target.go
+++ b/pkg/target/target.go
@@ -40,9 +40,10 @@ type ErrPayload struct {
 // FQDN, PrimaryIPv4, and PrimaryIPv6 are used by plugins to contact the target, set as many as possible for maximum plugin compatibility.
 // Plugins are generally expected to attempt contacting devices via FQDN, IPv4, and IPv6. Note there is no way to enforce this and more specialized plugins might only support a subset.
 type Target struct {
-	ID                       string
-	FQDN                     string
-	PrimaryIPv4, PrimaryIPv6 net.IP
+	ID          string `json:"ID"`
+	FQDN        string `json:"FQDN,omitempty"`
+	PrimaryIPv4 net.IP `json:"PrimaryIPv4,omitempty"`
+	PrimaryIPv6 net.IP `json:"PrimaryIPv6,omitempty"`
 }
 
 func (t *Target) String() string {
@@ -50,16 +51,16 @@ func (t *Target) String() string {
 		return "(*Target)(nil)"
 	}
 	var res strings.Builder
-	res.WriteString(fmt.Sprintf("Target{ID: \"%s\"", t.ID))
+	res.WriteString(fmt.Sprintf(`Target{ID: "%s"`, t.ID))
 	// deref params if they are set, to be more useful than %v
 	if t.FQDN != "" {
-		res.WriteString(fmt.Sprintf(", FQDN: \"%s\"", t.FQDN))
+		res.WriteString(fmt.Sprintf(`, FQDN: "%s"`, t.FQDN))
 	}
 	if t.PrimaryIPv4 != nil {
-		res.WriteString(fmt.Sprintf(", PrimaryIPv4: \"%v\"", t.PrimaryIPv4))
+		res.WriteString(fmt.Sprintf(`, PrimaryIPv4: "%v"`, t.PrimaryIPv4))
 	}
 	if t.PrimaryIPv6 != nil {
-		res.WriteString(fmt.Sprintf(", PrimaryIPv6: \"%v\"", t.PrimaryIPv6))
+		res.WriteString(fmt.Sprintf(`, PrimaryIPv6: "%v"`, t.PrimaryIPv6))
 	}
 	res.WriteString("}")
 	return res.String()
diff --git a/pkg/target/target_test.go b/pkg/target/target_test.go
index 7ee2b87c..0c1bb7a2 100644
--- a/pkg/target/target_test.go
+++ b/pkg/target/target_test.go
@@ -6,6 +6,8 @@
 package target
 
 import (
+	"encoding/json"
+	"net"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -21,3 +23,28 @@ func TestNilTarget(t *testing.T) {
 	}()
 	require.Nil(t, recoverResult)
 }
+
+func TestTargetStringification(t *testing.T) {
+	var t0 *Target
+	require.Equal(t, `(*Target)(nil)`, t0.String())
+
+	t1 := &Target{ID: "123"}
+	require.Equal(t, `Target{ID: "123"}`, t1.String())
+	tj1, _ := json.Marshal(t1)
+	require.Equal(t, `{"ID":"123"}`, string(tj1))
+
+	t2 := &Target{FQDN: "example.com"}
+	require.Equal(t, `Target{ID: "", FQDN: "example.com"}`, t2.String())
+	tj2, _ := json.Marshal(t2)
+	require.Equal(t, `{"ID":"","FQDN":"example.com"}`, string(tj2))
+
+	t3 := &Target{ID: "123", FQDN: "example.com", PrimaryIPv4: net.IPv4(1, 2, 3, 4)}
+	require.Equal(t, `Target{ID: "123", FQDN: "example.com", PrimaryIPv4: "1.2.3.4"}`, t3.String())
+	tj3, _ := json.Marshal(t3)
+	require.Equal(t, `{"ID":"123","FQDN":"example.com","PrimaryIPv4":"1.2.3.4"}`, string(tj3))
+
+	t4 := &Target{ID: "123", FQDN: "example.com", PrimaryIPv6: net.IPv6loopback}
+	require.Equal(t, `Target{ID: "123", FQDN: "example.com", PrimaryIPv6: "::1"}`, t4.String())
+	tj4, _ := json.Marshal(t4)
+	require.Equal(t, `{"ID":"123","FQDN":"example.com","PrimaryIPv6":"::1"}`, string(tj4))
+}