Resolve PR comments

pkg/jsonmerge/array_test.go

@@ -69,3 +69,18 @@ func TestArrayMerger_multiplePages(t *testing.T) {
 
 	require.NoError(t, merger.Close())
 }
+
+func TestArrayMerger_emptyObject(t *testing.T) {
+	merger := NewArrayMerger()
+	w := &bytes.Buffer{}
+
+	r1 := bytes.NewBufferString(`{}`)
+	p1 := merger.NewPage(r1, true)
+	n, err := io.Copy(w, p1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(2), n)
+	assert.NoError(t, p1.Close())
+	assert.Equal(t, `{}`, w.String())
+
+	require.NoError(t, merger.Close())
+}

pkg/jsonmerge/object.go

@@ -46,21 +46,14 @@ type objectMergerPage struct {
 	buffer bytes.Buffer
 }
 
+// Read caches the data in an internal buffer to be merged in Close.
+// No data is copied into p so it's not written to stdout.
 func (page *objectMergerPage) Read(p []byte) (int, error) {
-	// Read into a temporary buffer to be merged and written later.
-	p = make([]byte, len(p))
-	n, err := page.Reader.Read(p)
-	if err != nil {
-		return 0, err
-	}
-	if n == 0 {
-		return 0, io.EOF
-	}
-
-	_, err = page.buffer.Write(p[:n])
+	_, err := io.CopyN(&page.buffer, page.Reader, int64(len(p)))
 	return 0, err
 }
 
+// Close converts the internal buffer to a JSON object and merges it with the final JSON object.
 func (page *objectMergerPage) Close() error {
 	var src map[string]interface{}
 

pkg/jsonmerge/object_test.go

@@ -72,3 +72,27 @@ func TestObjectMerger_multiplePages(t *testing.T) {
 	require.NoError(t, merger.Close())
 	assert.JSONEq(t, `{"a":1,"b":3,"c":{"d":4},"arr":["a","b","c","d"]}`, w.String())
 }
+
+func TestObjectMerger_invalidJSON(t *testing.T) {
+	w := &bytes.Buffer{}
+	merger := NewObjectMerger(w)
+
+	r1 := bytes.NewBufferString(`invalid`)
+	p1 := merger.NewPage(r1, true)
+	n, err := io.Copy(w, p1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(0), n)
+	assert.Error(t, p1.Close())
+}
+
+func TestObjectMerger_array(t *testing.T) {
+	w := &bytes.Buffer{}
+	merger := NewObjectMerger(w)
+
+	r1 := bytes.NewBufferString(`[]`)
+	p1 := merger.NewPage(r1, true)
+	n, err := io.Copy(w, p1)
+	require.NoError(t, err)
+	assert.Equal(t, int64(0), n)
+	assert.Error(t, p1.Close())
+}