Merge pull request #3251 from AnnMarieW/fix-upload-style

fix upload style

Author: T4rk1n

CHANGELOG.md

@@ -7,6 +7,9 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ## Changed
 - [#3113](https://github.com/plotly/dash/pull/3113) Adjusted background polling requests to strip the data from the request, this allows for context to flow as normal. This addresses issue [#3111](https://github.com/plotly/dash/pull/3111)
 
+## Fixed
+- [#3251](https://github.com/plotly/dash/pull/3251). Prevented default styles from overriding `className_*` props in `dcc.Upload` component.
+
 
 ## [3.0.1] - 2025-03-24
 

components/dash-core-components/src/fragments/Upload.react.js

@@ -64,6 +64,11 @@ export default class Upload extends Component {
             style_reject,
             style_disabled,
         } = this.props;
+
+        const activeStyle = className_active ? undefined : style_active;
+        const disabledStyle = className_disabled ? undefined : style_disabled;
+        const rejectStyle = className_reject ? undefined : style_reject;
+
         return (
             <LoadingElement id={id}>
                 <Dropzone
@@ -79,9 +84,9 @@ export default class Upload extends Component {
                     rejectClassName={className_reject}
                     disabledClassName={className_disabled}
                     style={style}
-                    activeStyle={style_active}
-                    rejectStyle={style_reject}
-                    disabledStyle={style_disabled}
+                    activeStyle={activeStyle}
+                    rejectStyle={rejectStyle}
+                    disabledStyle={disabledStyle}
                 >
                     {children}
                 </Dropzone>

components/dash-core-components/tests/integration/upload/test_children_accept_any_component.py

@@ -28,10 +28,32 @@ def test_upca001_upload_children_gallery(dash_dcc):
                     "textAlign": "center",
                 },
             ),
+            dcc.Upload(
+                "upload",
+                disabled=True,
+                className_disabled="upload-disabled",
+                id="upload",
+            ),
+            dcc.Upload("upload", disabled=True, id="upload-no-className"),
         ]
     )
     dash_dcc.start_server(app)
     time.sleep(0.5)
     dash_dcc.percy_snapshot("upca001 children gallery")
 
+    first_child = dash_dcc.find_element("#upload").find_element_by_css_selector(
+        ":first-child"
+    )
+    # Check that there is no default style since className is specified
+    style = first_child.get_attribute("style")
+    assert "opacity: 0.5" not in style
+
+    first_child = dash_dcc.find_element(
+        "#upload-no-className"
+    ).find_element_by_css_selector(":first-child")
+
+    # Check that there is default style since no className is specified
+    style = first_child.get_attribute("style")
+    assert "opacity: 0.5" in style
+
     assert dash_dcc.get_logs() == []