Enable empty DatabaseQueryFilter (#15)

* Add test for "DatabaseQuery"

* Fix DatabaseQuery Filter field type

* Assert database query JSON omit logic in `Client` tests

Co-authored-by: Alexandre Falardeau <asfal@AsFal-Laptop.local>
Co-authored-by: David Stotijn <dstotijn@gmail.com>

client_test.go

@@ -406,7 +406,7 @@ func TestQueryDatabase(t *testing.T) {
 		{
 			name: "with query, successful response",
 			query: &notion.DatabaseQuery{
-				Filter: notion.DatabaseQueryFilter{
+				Filter: &notion.DatabaseQueryFilter{
 					Property: "Name",
 					Text: &notion.TextDatabaseQueryFilter{
 						Contains: "foobar",
@@ -775,7 +775,7 @@ func TestQueryDatabase(t *testing.T) {
 			expError: nil,
 		},
 		{
-			name:  "without query, successful response",
+			name:  "without query, doesn't send POST body",
 			query: nil,
 			respBody: func(_ *http.Request) io.Reader {
 				return strings.NewReader(
@@ -796,6 +796,28 @@ func TestQueryDatabase(t *testing.T) {
 			},
 			expError: nil,
 		},
+		{
+			name:  "with non nil query, but without fields, omits all fields from POST body",
+			query: &notion.DatabaseQuery{},
+			respBody: func(_ *http.Request) io.Reader {
+				return strings.NewReader(
+					`{
+						"object": "list",
+						"results": [],
+						"next_cursor": null,
+						"has_more": false
+					}`,
+				)
+			},
+			respStatusCode: http.StatusOK,
+			expPostBody:    map[string]interface{}{},
+			expResponse: notion.DatabaseQueryResponse{
+				Results:    []notion.Page{},
+				HasMore:    false,
+				NextCursor: nil,
+			},
+			expError: nil,
+		},
 		{
 			name: "error response",
 			respBody: func(_ *http.Request) io.Reader {

database.go

@@ -91,10 +91,10 @@ type DatabaseProperty struct {
 
 // DatabaseQuery is used for quering a database.
 type DatabaseQuery struct {
-	Filter      DatabaseQueryFilter `json:"filter,omitempty"`
-	Sorts       []DatabaseQuerySort `json:"sorts,omitempty"`
-	StartCursor string              `json:"start_cursor,omitempty"`
-	PageSize    int                 `json:"page_size,omitempty"`
+	Filter      *DatabaseQueryFilter `json:"filter,omitempty"`
+	Sorts       []DatabaseQuerySort  `json:"sorts,omitempty"`
+	StartCursor string               `json:"start_cursor,omitempty"`
+	PageSize    int                  `json:"page_size,omitempty"`
 }
 
 // DatabaseQueryResponse contains the results and pagination data from a query request.