gistfile1.diff

diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go
index 1ce679d..f831e58 100644
--- a/src/database/sql/sql.go
+++ b/src/database/sql/sql.go
@@ -14,6 +14,7 @@ package sql
 
 import (
 	"database/sql/driver"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -24,6 +25,7 @@ import (
 )
 
 var drivers = make(map[string]driver.Driver)
+var jsonNull = []byte("null")
 
 // Register makes a database driver available by the provided name.
 // If Register is called twice with the same name or if driver is nil,
@@ -94,6 +96,14 @@ func (ns NullString) Value() (driver.Value, error) {
 	return ns.String, nil
 }
 
+// MarshalJSON implements the json.Marshaler interface.
+func (ns NullString) MarshalJSON() ([]byte, error) {
+	if ns.Valid {
+		return json.Marshal(ns.String)
+	}
+	return jsonNull, nil
+}
+
 // NullInt64 represents an int64 that may be null.
 // NullInt64 implements the Scanner interface so
 // it can be used as a scan destination, similar to NullString.
@@ -120,6 +130,14 @@ func (n NullInt64) Value() (driver.Value, error) {
 	return n.Int64, nil
 }
 
+// MarshalJSON implements the json.Marshaler interface.
+func (n NullInt64) MarshalJSON() ([]byte, error) {
+	if n.Valid {
+		return json.Marshal(n.Int64)
+	}
+	return jsonNull, nil
+}
+
 // NullFloat64 represents a float64 that may be null.
 // NullFloat64 implements the Scanner interface so
 // it can be used as a scan destination, similar to NullString.
@@ -146,6 +164,14 @@ func (n NullFloat64) Value() (driver.Value, error) {
 	return n.Float64, nil
 }
 
+// MarshalJSON implements the json.Marshaler interface.
+func (n NullFloat64) MarshalJSON() ([]byte, error) {
+	if n.Valid {
+		return json.Marshal(n.Float64)
+	}
+	return jsonNull, nil
+}
+
 // NullBool represents a bool that may be null.
 // NullBool implements the Scanner interface so
 // it can be used as a scan destination, similar to NullString.
@@ -172,6 +198,14 @@ func (n NullBool) Value() (driver.Value, error) {
 	return n.Bool, nil
 }
 
+// MarshalJSON implements the json.Marshaler interface.
+func (n NullBool) MarshalJSON() ([]byte, error) {
+	if n.Valid {
+		return json.Marshal(n.Bool)
+	}
+	return jsonNull, nil
+}
+
 // Scanner is an interface used by Scan.
 type Scanner interface {
 	// Scan assigns a value from a database driver.
diff --git a/src/database/sql/sql_test.go b/src/database/sql/sql_test.go
index 60bdefa..61bf455 100644
--- a/src/database/sql/sql_test.go
+++ b/src/database/sql/sql_test.go
@@ -6,6 +6,7 @@ package sql
 
 import (
 	"database/sql/driver"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"math/rand"
@@ -840,6 +841,37 @@ func nullTestRun(t *testing.T, spec nullTestSpec) {
 	}
 }
 
+var nullJsonTests = []struct {
+	value interface{}
+	json  string
+}{
+	{NullString{"not null", true}, `"not null"`},
+	{NullString{"not null", false}, `null`},
+	{NullString{"", true}, `""`},
+	{NullString{"", false}, `null`},
+	{NullInt64{123, true}, `123`},
+	{NullInt64{123, false}, `null`},
+	{NullFloat64{123.4, true}, `123.4`},
+	{NullFloat64{123.4, false}, `null`},
+	{NullBool{true, true}, `true`},
+	{NullBool{false, true}, `false`},
+	{NullBool{true, false}, `null`},
+	{NullBool{false, false}, `null`},
+}
+
+func TestNullJson(t *testing.T) {
+	for _, jt := range nullJsonTests {
+		b, err := json.Marshal(jt.value)
+		if err != nil {
+			t.Fatal(err)
+		}
+		s := string(b)
+		if s != jt.json {
+			t.Fatalf("expected %v; got %v: err", jt.json, s)
+		}
+	}
+}
+
 // golang.org/issue/4859
 func TestQueryRowNilScanDest(t *testing.T) {
 	db := newTestDB(t, "people")