GODRIVER-2119 implement methods required to use as a map key

Author: Luberry

bson/primitive/objectid.go

@@ -99,6 +99,20 @@ func (id ObjectID) MarshalJSON() ([]byte, error) {
 	return json.Marshal(id.Hex())
 }
 
+// MarshalText returns the ObjectID as text
+// Implementing this allows us to use the ObjectID as a map key
+// when marshalling json.
+func (id ObjectID) MarshalText() ([]byte, error) {
+	return []byte(id.Hex()), nil
+}
+
+// UnmarshalText converts a text ObjectID into a byte string
+// Implementing this allows us to use the ObjectID as a map key
+// when marshalling json.
+func (id ObjectID) UnmarshalText(b []byte) error {
+	return id.UnmarshalJSON(b)
+}
+
 // UnmarshalJSON populates the byte slice with the ObjectID. If the byte slice is 24 bytes long, it
 // will be populated with the hex representation of the ObjectID. If the byte slice is twelve bytes
 // long, it will be populated with the BSON representation of the ObjectID. This method also accepts empty strings and

bson/primitive/objectid_test.go

@@ -172,6 +172,37 @@ func TestCounterOverflow(t *testing.T) {
 	require.Equal(t, uint32(0), objectIDCounter)
 }
 
+func TestObjectID_MarshalJSONMap(t *testing.T) {
+	type mapOID struct {
+		Map map[ObjectID]string
+	}
+
+	oid := NewObjectID()
+	expectedJson := []byte(fmt.Sprintf(`{"Map":{%q:"foo"}}`, oid.Hex()))
+	data := mapOID{
+		Map: map[ObjectID]string{oid: "foo"},
+	}
+
+	out, err := json.Marshal(&data)
+	require.NoError(t, err)
+	require.Equal(t, expectedJson, out)
+}
+
+func TestObjectID_UnmarshalJSONMap(t *testing.T) {
+	type mapOID struct {
+		Map map[ObjectID]string
+	}
+	oid := NewObjectID()
+	mapOIDJson := []byte(fmt.Sprintf(`{"Map":{%q:"foo"}}`, oid.Hex()))
+	expectedData := mapOID{
+		Map: map[ObjectID]string{oid: "foo"},
+	}
+
+	data := mapOID{}
+	err := json.Unmarshal(mapOIDJson, &data)
+	require.NoError(t, err)
+	require.Equal(t, expectedData, data)
+}
 func TestObjectID_UnmarshalJSON(t *testing.T) {
 	oid := NewObjectID()