Add MarshalJSON to a few types

pgtype/int2.go

@@ -195,3 +195,16 @@ func (src Int2) Value() (driver.Value, error) {
 		return nil, errUndefined
 	}
 }
+
+func (src Int2) MarshalJSON() ([]byte, error) {
+	switch src.Status {
+	case Present:
+		return []byte(strconv.FormatInt(int64(src.Int), 10)), nil
+	case Null:
+		return []byte("null"), nil
+	case Undefined:
+		return []byte("undefined"), nil
+	}
+
+	return nil, errBadStatus
+}

pgtype/int4.go

@@ -186,3 +186,16 @@ func (src Int4) Value() (driver.Value, error) {
 		return nil, errUndefined
 	}
 }
+
+func (src Int4) MarshalJSON() ([]byte, error) {
+	switch src.Status {
+	case Present:
+		return []byte(strconv.FormatInt(int64(src.Int), 10)), nil
+	case Null:
+		return []byte("null"), nil
+	case Undefined:
+		return []byte("undefined"), nil
+	}
+
+	return nil, errBadStatus
+}

pgtype/int8.go

@@ -172,3 +172,16 @@ func (src Int8) Value() (driver.Value, error) {
 		return nil, errUndefined
 	}
 }
+
+func (src Int8) MarshalJSON() ([]byte, error) {
+	switch src.Status {
+	case Present:
+		return []byte(strconv.FormatInt(src.Int, 10)), nil
+	case Null:
+		return []byte("null"), nil
+	case Undefined:
+		return []byte("undefined"), nil
+	}
+
+	return nil, errBadStatus
+}

pgtype/pgtype.go

@@ -129,6 +129,7 @@ type TextEncoder interface {
 }
 
 var errUndefined = errors.New("cannot encode status undefined")
+var errBadStatus = errors.New("invalid status")
 
 type DataType struct {
 	Value Value

pgtype/text.go

@@ -2,6 +2,7 @@ package pgtype
 
 import (
 	"database/sql/driver"
+	"encoding/json"
 	"fmt"
 	"io"
 )
@@ -134,3 +135,16 @@ func (src Text) Value() (driver.Value, error) {
 		return nil, errUndefined
 	}
 }
+
+func (src Text) MarshalJSON() ([]byte, error) {
+	switch src.Status {
+	case Present:
+		return json.Marshal(src.String)
+	case Null:
+		return []byte("null"), nil
+	case Undefined:
+		return []byte("undefined"), nil
+	}
+
+	return nil, errBadStatus
+}

pgtype/varchar.go

@@ -49,3 +49,7 @@ func (dst *Varchar) Scan(src interface{}) error {
 func (src Varchar) Value() (driver.Value, error) {
 	return (Text)(src).Value()
 }
+
+func (src Varchar) MarshalJSON() ([]byte, error) {
+	return (Text)(src).MarshalJSON()
+}