From 7a3e774a5210e09e9c9471252e5e7f276e3d455c Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Tue, 14 Jul 2020 11:58:03 -0500
Subject: [PATCH] Fix ArrayType DecodeBinary empty array breaks future reads

---
 array_type.go      |  8 ++++++--
 array_type_test.go | 22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/array_type.go b/array_type.go
index 32ce7ac4..04b8710c 100644
--- a/array_type.go
+++ b/array_type.go
@@ -185,8 +185,12 @@ func (dst *ArrayType) DecodeBinary(ci *ConnInfo, src []byte) error {
 		return err
 	}
 
+	var elements []ValueTranscoder
+
 	if len(arrayHeader.Dimensions) == 0 {
-		*dst = ArrayType{dimensions: arrayHeader.Dimensions, status: Present}
+		dst.elements = elements
+		dst.dimensions = arrayHeader.Dimensions
+		dst.status = Present
 		return nil
 	}
 
@@ -195,7 +199,7 @@ func (dst *ArrayType) DecodeBinary(ci *ConnInfo, src []byte) error {
 		elementCount *= d.Length
 	}
 
-	elements := make([]ValueTranscoder, elementCount)
+	elements = make([]ValueTranscoder, elementCount)
 
 	for i := range elements {
 		elem := dst.newElement()
diff --git a/array_type_test.go b/array_type_test.go
index 0f296bb5..626df4dc 100644
--- a/array_type_test.go
+++ b/array_type_test.go
@@ -60,3 +60,25 @@ func TestArrayTypeTranscode(t *testing.T) {
 
 	require.EqualValues(t, []string{"red", "green", "blue"}, dstStrings)
 }
+
+func TestArrayTypeEmptyArrayDoesNotBreakArrayType(t *testing.T) {
+	conn := testutil.MustConnectPgx(t)
+	defer testutil.MustCloseContext(t, conn)
+
+	conn.ConnInfo().RegisterDataType(pgtype.DataType{
+		Value: pgtype.NewArrayType("_text", pgtype.TextOID, func() pgtype.ValueTranscoder { return &pgtype.Text{} }),
+		Name:  "_text",
+		OID:   pgtype.TextArrayOID,
+	})
+
+	var dstStrings []string
+	err := conn.QueryRow(context.Background(), "select '{}'::text[]").Scan(&dstStrings)
+	require.NoError(t, err)
+
+	require.EqualValues(t, []string{}, dstStrings)
+
+	err = conn.QueryRow(context.Background(), "select $1::text[]", []string{"red", "green", "blue"}).Scan(&dstStrings)
+	require.NoError(t, err)
+
+	require.EqualValues(t, []string{"red", "green", "blue"}, dstStrings)
+}