From 329cb45913691e9e0369a94fa2cf059c237307a7 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Sat, 11 Jan 2025 10:47:57 -0600
Subject: [PATCH 1/2] XMLCodec: fix DecodeValue to return a []byte

Previously, DecodeValue would always return nil with the default
Unmarshal function.

fixes https://github.com/jackc/pgx/issues/2227
---
 pgtype/xml.go      |  6 +++---
 pgtype/xml_test.go | 29 +++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/pgtype/xml.go b/pgtype/xml.go
index 79e3698a4..1d159cf1b 100644
--- a/pgtype/xml.go
+++ b/pgtype/xml.go
@@ -192,7 +192,7 @@ func (c *XMLCodec) DecodeValue(m *Map, oid uint32, format int16, src []byte) (an
 		return nil, nil
 	}
 
-	var dst any
-	err := c.Unmarshal(src, &dst)
-	return dst, err
+	dstBuf := make([]byte, len(src))
+	copy(dstBuf, src)
+	return dstBuf, nil
 }
diff --git a/pgtype/xml_test.go b/pgtype/xml_test.go
index 0f755e96f..211859147 100644
--- a/pgtype/xml_test.go
+++ b/pgtype/xml_test.go
@@ -97,3 +97,32 @@ func TestXMLCodecPointerToPointerToString(t *testing.T) {
 		require.Nil(t, s)
 	})
 }
+
+func TestXMLCodecDecodeValue(t *testing.T) {
+	skipCockroachDB(t, "CockroachDB does not support XML.")
+	defaultConnTestRunner.RunTest(context.Background(), t, func(ctx context.Context, _ testing.TB, conn *pgx.Conn) {
+		for _, tt := range []struct {
+			sql      string
+			expected any
+		}{
+			{
+				sql:      `select '<foo>bar</foo>'::xml`,
+				expected: []byte("<foo>bar</foo>"),
+			},
+		} {
+			t.Run(tt.sql, func(t *testing.T) {
+				rows, err := conn.Query(ctx, tt.sql)
+				require.NoError(t, err)
+
+				for rows.Next() {
+					values, err := rows.Values()
+					require.NoError(t, err)
+					require.Len(t, values, 1)
+					require.Equal(t, tt.expected, values[0])
+				}
+
+				require.NoError(t, rows.Err())
+			})
+		}
+	})
+}

From 03f08abda3e096464b7ae894e8c12c322e3f73a3 Mon Sep 17 00:00:00 2001
From: Jack Christensen <jack@jackchristensen.com>
Date: Sat, 11 Jan 2025 11:26:46 -0600
Subject: [PATCH 2/2] Fix in Unmarshal function rather than DecodeValue

This preserves backwards compatibility in the unlikely event someone is
using an alternative XML unmarshaler that does support unmarshalling
into *any.
---
 pgtype/pgtype_default.go | 20 +++++++++++++++++++-
 pgtype/xml.go            |  6 +++---
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/pgtype/pgtype_default.go b/pgtype/pgtype_default.go
index 9496cb974..8cb512fa5 100644
--- a/pgtype/pgtype_default.go
+++ b/pgtype/pgtype_default.go
@@ -91,7 +91,25 @@ func initDefaultMap() {
 	defaultMap.RegisterType(&Type{Name: "varchar", OID: VarcharOID, Codec: TextCodec{}})
 	defaultMap.RegisterType(&Type{Name: "xid", OID: XIDOID, Codec: Uint32Codec{}})
 	defaultMap.RegisterType(&Type{Name: "xid8", OID: XID8OID, Codec: Uint64Codec{}})
-	defaultMap.RegisterType(&Type{Name: "xml", OID: XMLOID, Codec: &XMLCodec{Marshal: xml.Marshal, Unmarshal: xml.Unmarshal}})
+	defaultMap.RegisterType(&Type{Name: "xml", OID: XMLOID, Codec: &XMLCodec{
+		Marshal: xml.Marshal,
+		// xml.Unmarshal does not support unmarshalling into *any. However, XMLCodec.DecodeValue calls Unmarshal with a
+		// *any. Wrap xml.Marshal with a function that copies the data into a new byte slice in this case. Not implementing
+		// directly in XMLCodec.DecodeValue to allow for the unlikely possibility that someone uses an alternative XML
+		// unmarshaler that does support unmarshalling into *any.
+		//
+		// https://github.com/jackc/pgx/issues/2227
+		// https://github.com/jackc/pgx/pull/2228
+		Unmarshal: func(data []byte, v any) error {
+			if v, ok := v.(*any); ok {
+				dstBuf := make([]byte, len(data))
+				copy(dstBuf, data)
+				*v = dstBuf
+				return nil
+			}
+			return xml.Unmarshal(data, v)
+		},
+	}})
 
 	// Range types
 	defaultMap.RegisterType(&Type{Name: "daterange", OID: DaterangeOID, Codec: &RangeCodec{ElementType: defaultMap.oidToType[DateOID]}})
diff --git a/pgtype/xml.go b/pgtype/xml.go
index 1d159cf1b..79e3698a4 100644
--- a/pgtype/xml.go
+++ b/pgtype/xml.go
@@ -192,7 +192,7 @@ func (c *XMLCodec) DecodeValue(m *Map, oid uint32, format int16, src []byte) (an
 		return nil, nil
 	}
 
-	dstBuf := make([]byte, len(src))
-	copy(dstBuf, src)
-	return dstBuf, nil
+	var dst any
+	err := c.Unmarshal(src, &dst)
+	return dst, err
 }