From fa48576ef06dab552af6a8c62feb5dcb37f75cfb Mon Sep 17 00:00:00 2001
From: Milos Pejanovic <pejan123@gmail.com>
Date: Mon, 20 Sep 2021 16:52:08 +0200
Subject: [PATCH] implement use case when null is set

---
 conflate_test.go              | 19 ++++++++++++++++++-
 go.sum                        |  1 -
 merge.go                      |  5 +++++
 testdata/test_not_nulled.yaml |  2 ++
 testdata/test_nulled.yaml     |  2 ++
 5 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 testdata/test_not_nulled.yaml
 create mode 100644 testdata/test_nulled.yaml

diff --git a/conflate_test.go b/conflate_test.go
index cf9c475..2c94b89 100644
--- a/conflate_test.go
+++ b/conflate_test.go
@@ -2,11 +2,12 @@ package conflate
 
 import (
 	gocontext "context"
-	"github.com/stretchr/testify/assert"
 	"net/http"
 	"os"
 	"sync"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 type TestData struct {
@@ -20,6 +21,11 @@ type TestData struct {
 	All           string `json:"all"`
 }
 
+type TestNulledData struct {
+	Foo string `yaml:"foo"`
+	Bar string `yaml:"bar"`
+}
+
 func TestFromFiles(t *testing.T) {
 	c, err := FromFiles("testdata/valid_parent.json")
 	assert.Nil(t, err)
@@ -318,3 +324,14 @@ func TestConflate_mergeDataError(t *testing.T) {
 	assert.NotNil(t, err)
 	assert.Contains(t, err.Error(), "Failed to merge")
 }
+
+func TestFromFilesNulled(t *testing.T) {
+	c, err := FromFiles("testdata/test_not_nulled.yaml", "testdata/test_nulled.yaml")
+	assert.Nil(t, err)
+	assert.NotNil(t, c)
+	var testData TestNulledData
+	err = c.Unmarshal(&testData)
+	assert.Nil(t, err)
+	assert.Equal(t, "foo", testData.Foo)
+	assert.Equal(t, "", testData.Bar)
+}
diff --git a/go.sum b/go.sum
index adefc0f..9596753 100644
--- a/go.sum
+++ b/go.sum
@@ -9,7 +9,6 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
-github.com/xeipuuv/gojsonpointer v0.0.0-20180127040702-4e3ac2762d5f h1:J9EGpcZtP0E/raorCMxlFGSTBrsSlaDGf3jU/qvAE2c=
 github.com/xeipuuv/gojsonpointer v0.0.0-20180127040702-4e3ac2762d5f/go.mod h1:N2zxlSyiKSe5eX1tZViRH5QA0qijqEDrYZiPEAiq3wU=
 github.com/xeipuuv/gojsonpointer v0.0.0-20190905194746-02993c407bfb h1:zGWFAtiMcyryUHoUjUJX0/lt1H2+i2Ka2n+D3DImSNo=
 github.com/xeipuuv/gojsonpointer v0.0.0-20190905194746-02993c407bfb/go.mod h1:N2zxlSyiKSe5eX1tZViRH5QA0qijqEDrYZiPEAiq3wU=
diff --git a/merge.go b/merge.go
index 0f39423..25d9077 100644
--- a/merge.go
+++ b/merge.go
@@ -64,6 +64,11 @@ func mergeMapRecursive(ctx context, toVal reflect.Value, fromVal reflect.Value,
 		return makeContextError(ctx, "The destination value must be a map[string]interface{}")
 	}
 	for name, fromProp := range fromProps {
+		// merge in explicit nil values
+		if fromProp == nil {
+			toProps[name] = nil
+			continue
+		}
 		if val := toProps[name]; val == nil {
 			toProps[name] = fromProp
 		} else {
diff --git a/testdata/test_not_nulled.yaml b/testdata/test_not_nulled.yaml
new file mode 100644
index 0000000..e7b26c8
--- /dev/null
+++ b/testdata/test_not_nulled.yaml
@@ -0,0 +1,2 @@
+foo: foo
+bar: bar
\ No newline at end of file
diff --git a/testdata/test_nulled.yaml b/testdata/test_nulled.yaml
new file mode 100644
index 0000000..596e0e3
--- /dev/null
+++ b/testdata/test_nulled.yaml
@@ -0,0 +1,2 @@
+foo: foo
+bar: null
\ No newline at end of file