client: allow nil body in DoJSON

client.go

@@ -61,6 +61,10 @@ func (c *Client) Do(req *http.Request) (*http.Response, error) {
 
 // JSON
 //
+// DoJSON, GetJSON, PostJSON, PutJSON, and DeleteJSON all set the appropriate
+// JSON headers and decode the response body into the target. Pass nil as
+// target to skip decoding — useful for endpoints that return no body (e.g.
+// 204 No Content).
 
 func (c *Client) DoJSON(req *http.Request, target any) error {
 	req.Header.Set("Content-Type", "application/json")
@@ -84,7 +88,12 @@ func (c *Client) DoJSON(req *http.Request, target any) error {
 		return fmt.Errorf("got %d code and response: %s", resp.StatusCode, string(body))
 	}
 
-	if err := json.NewDecoder(resp.Body).Decode(&target); err != nil {
+	if target == nil {
+		_, _ = io.Copy(io.Discard, resp.Body)
+		return nil
+	}
+
+	if err := json.NewDecoder(resp.Body).Decode(target); err != nil {
 		return fmt.Errorf("got %d code and failed to decode response body: %w", resp.StatusCode, err)
 	}
 	return nil

client_test.go

@@ -71,6 +71,19 @@ func TestClientDoJSON(t *testing.T) {
 	assert.Equal(t, "joebob", user.Name)
 }
 
+func TestClientDoJSONNilTarget204(t *testing.T) {
+	handler, client, cleanup := setup(t)
+	defer cleanup()
+
+	handler.On("HandleWithHeaders", "DELETE", "/users/1", jsonHeaderMatcher, mock.Anything).Return(httpmock.Response{
+		Status: http.StatusNoContent,
+	})
+
+	req, err := http.NewRequest("DELETE", "/users/1", nil)
+	require.NoError(t, err)
+	require.NoError(t, client.DoJSON(req, nil))
+}
+
 type TestUser struct {
 	ID   int    `json:"id,omitempty"`
 	Name string `json:"name"`