fix: set maxFiles to Infinity when setting a MultiFileReceiver (#6253)

vaadin-upload-flow-parent/vaadin-upload-flow-integration-tests/src/main/java/com/vaadin/flow/component/upload/tests/SwitchReceiversPage.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2000-2024 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ *
+ */
+package com.vaadin.flow.component.upload.tests;
+
+import com.vaadin.flow.component.html.NativeButton;
+
+import com.vaadin.flow.component.html.Div;
+import com.vaadin.flow.component.upload.Upload;
+import com.vaadin.flow.component.upload.receivers.MemoryBuffer;
+import com.vaadin.flow.component.upload.receivers.MultiFileMemoryBuffer;
+import com.vaadin.flow.router.Route;
+
+@Route("vaadin-upload/switch-receivers")
+public class SwitchReceiversPage extends Div {
+
+    public SwitchReceiversPage() {
+        Upload upload = new Upload();
+
+        NativeButton setSingleFileReceiver = new NativeButton(
+                "Set single file receiver", event -> {
+                    MemoryBuffer buffer = new MemoryBuffer();
+                    upload.setReceiver(buffer);
+                });
+        setSingleFileReceiver.setId("set-single-file-receiver");
+
+        NativeButton setMultiFileReceiver = new NativeButton(
+                "Set multi file receiver", event -> {
+                    MultiFileMemoryBuffer buffer = new MultiFileMemoryBuffer();
+                    upload.setReceiver(buffer);
+                });
+        setMultiFileReceiver.setId("set-multi-file-receiver");
+
+        add(upload, setSingleFileReceiver, setMultiFileReceiver);
+    }
+
+}

vaadin-upload-flow-parent/vaadin-upload-flow-integration-tests/src/test/java/com/vaadin/flow/component/upload/tests/SwitchReceiversIT.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2000-2024 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.component.upload.tests;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.vaadin.flow.component.upload.testbench.UploadElement;
+import com.vaadin.flow.testutil.TestPath;
+
+@TestPath("vaadin-upload/switch-receivers")
+public class SwitchReceiversIT extends AbstractUploadIT {
+
+    private UploadElement upload;
+
+    @Before
+    public void init() {
+        open();
+        upload = $(UploadElement.class).first();
+    }
+
+    @Test
+    public void switchBetweenSingleAndMultiFileReceiver_assertMaxFilesProperty() {
+        $("button").id("set-single-file-receiver").click();
+        Assert.assertEquals(
+                "The maxFiles property should equal 1 when single file receiver is set",
+                1, (int) upload.getPropertyInteger("maxFiles"));
+
+        $("button").id("set-multi-file-receiver").click();
+        Assert.assertTrue(
+                "The maxFiles property should equal Infinity when multi file receiver is set",
+                (boolean) executeScript(
+                        "return arguments[0].maxFiles === Infinity", upload));
+
+        $("button").id("set-single-file-receiver").click();
+        Assert.assertEquals(
+                "The maxFiles property should equal 1 when single file receiver is set",
+                1, (int) upload.getPropertyInteger("maxFiles"));
+    }
+}

vaadin-upload-flow-parent/vaadin-upload-flow/src/main/java/com/vaadin/flow/component/upload/Upload.java

@@ -633,10 +633,11 @@ public Receiver getReceiver() {
      */
     public void setReceiver(Receiver receiver) {
         this.receiver = receiver;
-        if (!(receiver instanceof MultiFileReceiver)) {
-            setMaxFiles(1);
+        if (receiver instanceof MultiFileReceiver) {
+            getElement().removeProperty("maxFiles");
+            getElement().executeJs("this.maxFiles = Infinity");
         } else {
-            getElement().removeAttribute("maxFiles");
+            setMaxFiles(1);
         }
     }
 

vaadin-upload-flow-parent/vaadin-upload-flow/src/test/java/com/vaadin/flow/component/upload/tests/UploadTest.java

@@ -3,6 +3,10 @@
 import com.vaadin.flow.component.upload.Upload;
 
 import org.junit.Test;
+import org.junit.Assert;
+
+import com.vaadin.flow.component.upload.receivers.MemoryBuffer;
+import com.vaadin.flow.component.upload.receivers.MultiFileMemoryBuffer;
 
 public class UploadTest {
 
@@ -11,4 +15,18 @@ public void uploadNewUpload() {
         // Test no NPE due missing UI when setAttribute is called.
         Upload upload = new Upload();
     }
+
+    @Test
+    public void switchBetweenSingleAndMultiFileReceiver_assertMaxFilesProperty() {
+        Upload upload = new Upload();
+
+        upload.setReceiver(new MemoryBuffer());
+        Assert.assertEquals(1, upload.getElement().getProperty("maxFiles", 0));
+
+        upload.setReceiver(new MultiFileMemoryBuffer());
+        Assert.assertNull(upload.getElement().getProperty("maxFiles"));
+
+        upload.setReceiver(new MemoryBuffer());
+        Assert.assertEquals(1, upload.getElement().getProperty("maxFiles", 0));
+    }
 }