Support nil pointers to value implementing driver.Valuer

fixes #339

README.md

@@ -79,6 +79,7 @@ skip tests for connection types that are not configured.
 
 To setup the normal test environment, first install these dependencies:
 
+    go get github.com/cockroachdb/apd
     go get github.com/hashicorp/go-version
     go get github.com/jackc/fake
     go get github.com/lib/pq

go_stdlib.go

@@ -0,0 +1,61 @@
+package pgx
+
+import (
+	"database/sql/driver"
+	"reflect"
+)
+
+// This file contains code copied from the Go standard library due to the
+// required function not being public.
+
+// Copyright (c) 2009 The Go Authors. All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// From database/sql/convert.go
+
+var valuerReflectType = reflect.TypeOf((*driver.Valuer)(nil)).Elem()
+
+// callValuerValue returns vr.Value(), with one exception:
+// If vr.Value is an auto-generated method on a pointer type and the
+// pointer is nil, it would panic at runtime in the panicwrap
+// method. Treat it like nil instead.
+// Issue 8415.
+//
+// This is so people can implement driver.Value on value types and
+// still use nil pointers to those types to mean nil/NULL, just like
+// string/*string.
+//
+// This function is mirrored in the database/sql/driver package.
+func callValuerValue(vr driver.Valuer) (v driver.Value, err error) {
+	if rv := reflect.ValueOf(vr); rv.Kind() == reflect.Ptr &&
+		rv.IsNil() &&
+		rv.Type().Elem().Implements(valuerReflectType) {
+		return nil, nil
+	}
+	return vr.Value()
+}

query_test.go

@@ -9,6 +9,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/cockroachdb/apd"
 	"github.com/jackc/pgx"
 	"github.com/jackc/pgx/pgtype"
 	satori "github.com/jackc/pgx/pgtype/ext/satori-uuid"
@@ -1001,6 +1002,27 @@ func TestConnQueryDatabaseSQLDriverValuer(t *testing.T) {
 	ensureConnValid(t, conn)
 }
 
+// https://github.com/jackc/pgx/issues/339
+func TestConnQueryDatabaseSQLDriverValuerWithAutoGeneratedPointerReceiver(t *testing.T) {
+	t.Parallel()
+
+	conn := mustConnect(t, *defaultConnConfig)
+	defer closeConn(t, conn)
+
+	mustExec(t, conn, "create temporary table t(n numeric)")
+
+	var d *apd.Decimal
+	commandTag, err := conn.Exec(`insert into t(n) values($1)`, d)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if commandTag != "INSERT 0 1" {
+		t.Fatalf("want %s, got %s", "INSERT 0 1", commandTag)
+	}
+
+	ensureConnValid(t, conn)
+}
+
 func TestConnQueryDatabaseSQLDriverValuerWithBinaryPgTypeThatAcceptsSameType(t *testing.T) {
 	t.Parallel()
 

values.go

@@ -32,7 +32,7 @@ func convertSimpleArgument(ci *pgtype.ConnInfo, arg interface{}) (interface{}, e
 
 	switch arg := arg.(type) {
 	case driver.Valuer:
-		return arg.Value()
+		return callValuerValue(arg)
 	case pgtype.TextEncoder:
 		buf, err := arg.EncodeText(ci, nil)
 		if err != nil {
@@ -150,7 +150,7 @@ func encodePreparedStatementArgument(ci *pgtype.ConnInfo, buf []byte, oid pgtype
 		if err != nil {
 			{
 				if arg, ok := arg.(driver.Valuer); ok {
-					v, err := arg.Value()
+					v, err := callValuerValue(arg)
 					if err != nil {
 						return nil, err
 					}
@@ -175,7 +175,7 @@ func encodePreparedStatementArgument(ci *pgtype.ConnInfo, buf []byte, oid pgtype
 	}
 
 	if arg, ok := arg.(driver.Valuer); ok {
-		v, err := arg.Value()
+		v, err := callValuerValue(arg)
 		if err != nil {
 			return nil, err
 		}
@@ -203,7 +203,7 @@ func chooseParameterFormatCode(ci *pgtype.ConnInfo, oid pgtype.OID, arg interfac
 		if _, ok := dt.Value.(pgtype.BinaryEncoder); ok {
 			if arg, ok := arg.(driver.Valuer); ok {
 				if err := dt.Value.Set(arg); err != nil {
-					if value, err := arg.Value(); err == nil {
+					if value, err := callValuerValue(arg); err == nil {
 						if _, ok := value.(string); ok {
 							return TextFormatCode
 						}