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Merge pull request #3481 from lfelipediniz/feat/add-folder-upload-support
feat: Add folder upload support to dcc.Upload component
2 parents 670cd51 + ca5515e commit 9e5d7c5

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‎CHANGELOG.md‎

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@@ -47,6 +47,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
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## [3.3.0] - 2025-11-12
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## Added
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- [#3464](https://github.com/plotly/dash/issues/3464) Add folder upload functionality to `dcc.Upload` component. When `multiple=True`, users can now select and upload entire folders in addition to individual files. The folder hierarchy is preserved in filenames (e.g., `folder/subfolder/file.txt`). Files within folders are filtered according to the `accept` prop. Folder support is available in Chrome, Edge, and Opera; other browsers gracefully fall back to file-only mode. The uploaded files use the same output API as multiple file uploads.
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- [#3395](https://github.com/plotly/dash/pull/3396) Add position argument to hooks.devtool
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- [#3403](https://github.com/plotly/dash/pull/3403) Add app_context to get_app, allowing to get the current app in routes.
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- [#3407](https://github.com/plotly/dash/pull/3407) Add `hidden` to callback arguments, hiding the callback from appearing in the devtool callback graph.

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

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@@ -110,10 +110,22 @@ Upload.propTypes = {
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min_size: PropTypes.number,
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/**
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* Allow dropping multiple files
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* Allow dropping multiple files.
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* When true, enables folder drag-and-drop support.
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* The folder hierarchy is preserved in filenames (e.g., 'folder/subfolder/file.txt').
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* Note: Folder drag-and-drop is supported in Chrome, Edge, and Opera.
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*/
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multiple: PropTypes.bool,
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/**
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* Enable folder selection in the file picker dialog.
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* When true with multiple=True, the file picker allows selecting folders instead of files.
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* Note: When folder selection is enabled, individual files cannot be selected via the button.
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* Use separate Upload components if you need both file and folder selection options.
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* Folder selection is supported in Chrome, Edge, and Opera.
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*/
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enable_folder_selection: PropTypes.bool,
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/**
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* HTML class name of the component
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*/
@@ -166,6 +178,7 @@ Upload.defaultProps = {
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max_size: -1,
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min_size: 0,
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multiple: false,
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enable_folder_selection: false,
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style: {},
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style_active: {
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borderStyle: 'solid',

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

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@@ -8,6 +8,142 @@ export default class Upload extends Component {
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constructor() {
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super();
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this.onDrop = this.onDrop.bind(this);
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this.getDataTransferItems = this.getDataTransferItems.bind(this);
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}
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// Check if file matches the accept criteria
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fileMatchesAccept(file, accept) {
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if (!accept) {
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return true;
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}
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const acceptList = Array.isArray(accept) ? accept : accept.split(',');
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const fileName = file.name.toLowerCase();
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const fileType = file.type.toLowerCase();
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return acceptList.some(acceptItem => {
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const item = acceptItem.trim().toLowerCase();
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// Exact MIME type match
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if (item === fileType) {
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return true;
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}
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// Wildcard MIME type (e.g., image/*)
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if (item.endsWith('/*')) {
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const wildcardSuffixLength = 2;
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const baseType = item.slice(0, -wildcardSuffixLength);
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return fileType.startsWith(baseType + '/');
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}
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// File extension match (e.g., .jpg)
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if (item.startsWith('.')) {
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return fileName.endsWith(item);
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}
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return false;
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});
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}
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// Recursively traverse folder structure and extract all files
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async traverseFileTree(item, path = '') {
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const {accept} = this.props;
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const files = [];
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if (item.isFile) {
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return new Promise(resolve => {
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item.file(file => {
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// Check if file matches accept criteria
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if (!this.fileMatchesAccept(file, accept)) {
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resolve([]);
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return;
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}
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// Preserve folder structure in file name
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const relativePath = path + file.name;
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Object.defineProperty(file, 'name', {
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writable: true,
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value: relativePath,
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});
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resolve([file]);
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});
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});
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} else if (item.isDirectory) {
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const dirReader = item.createReader();
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return new Promise(resolve => {
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const readEntries = () => {
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dirReader.readEntries(async entries => {
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if (entries.length === 0) {
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resolve(files);
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} else {
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for (const entry of entries) {
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const entryFiles = await this.traverseFileTree(
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entry,
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path + item.name + '/'
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);
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files.push(...entryFiles);
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}
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// Continue reading (directories may have more than 100 entries)
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readEntries();
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}
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});
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};
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readEntries();
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});
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}
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return files;
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}
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// Custom data transfer handler that supports folders
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async getDataTransferItems(event) {
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const {multiple} = this.props;
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// If multiple is not enabled, use default behavior (files only)
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if (!multiple) {
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if (event.dataTransfer) {
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return Array.from(event.dataTransfer.files);
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} else if (event.target && event.target.files) {
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return Array.from(event.target.files);
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}
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return [];
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}
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// Handle drag-and-drop with folder support when multiple=true
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if (event.dataTransfer && event.dataTransfer.items) {
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const items = Array.from(event.dataTransfer.items);
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const files = [];
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for (const item of items) {
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if (item.kind === 'file') {
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const entry = item.webkitGetAsEntry
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? item.webkitGetAsEntry()
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: null;
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if (entry) {
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const entryFiles = await this.traverseFileTree(entry);
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files.push(...entryFiles);
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} else {
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// Fallback for browsers without webkitGetAsEntry
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const file = item.getAsFile();
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if (file) {
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files.push(file);
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}
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}
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}
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}
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return files;
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}
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// Handle file picker (already works with webkitdirectory attribute)
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if (event.target && event.target.files) {
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return Array.from(event.target.files);
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}
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// Fallback
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if (event.dataTransfer && event.dataTransfer.files) {
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return Array.from(event.dataTransfer.files);
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}
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return [];
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}
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onDrop(files) {
@@ -55,6 +191,7 @@ export default class Upload extends Component {
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max_size,
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min_size,
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multiple,
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enable_folder_selection,
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className,
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className_active,
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className_reject,
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const disabledStyle = className_disabled ? undefined : style_disabled;
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const rejectStyle = className_reject ? undefined : style_reject;
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// Enable folder selection in file picker when explicitly requested
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// Note: This makes individual files unselectable in the file picker
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const inputProps =
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multiple && enable_folder_selection
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? {
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webkitdirectory: 'true',
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directory: 'true',
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mozdirectory: 'true',
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}
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: {};
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return (
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<LoadingElement id={id}>
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<Dropzone
@@ -79,6 +227,8 @@ export default class Upload extends Component {
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maxSize={max_size === -1 ? Infinity : max_size}
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minSize={min_size}
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multiple={multiple}
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inputProps={inputProps}
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getDataTransferItems={this.getDataTransferItems}
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className={className}
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activeClassName={className_active}
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rejectClassName={className_reject}

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

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from dash import Dash, Input, Output, dcc, html
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def test_upfd001_folder_upload_with_enable_folder_selection(dash_dcc):
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"""
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Test that folder upload is enabled when enable_folder_selection=True.
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Note: Full end-to-end testing of folder upload functionality is limited
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by Selenium's capabilities. This test verifies the component renders
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correctly with enable_folder_selection=True which enables folder support.
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"""
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app = Dash(__name__)
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app.layout = html.Div(
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[
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html.Div("Folder Upload Test", id="title"),
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dcc.Upload(
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id="upload-folder",
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children=html.Div(
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["Drag and Drop or ", html.A("Select Folder")]
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),
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style={
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"width": "100%",
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"height": "60px",
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"lineHeight": "60px",
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"borderWidth": "1px",
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"borderStyle": "dashed",
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"borderRadius": "5px",
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"textAlign": "center",
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},
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multiple=True,
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enable_folder_selection=True, # Enables folder selection
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accept=".txt,.csv", # Test accept filtering
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),
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html.Div(id="output"),
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]
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)
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@app.callback(
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Output("output", "children"),
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[Input("upload-folder", "contents")],
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)
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def update_output(contents_list):
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if contents_list is not None:
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return html.Div(f"Uploaded {len(contents_list)} file(s)", id="file-count")
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return html.Div("No files uploaded")
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dash_dcc.start_server(app)
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# Verify the component renders
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dash_dcc.wait_for_text_to_equal("#title", "Folder Upload Test")
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# Verify the upload component and input are present
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dash_dcc.wait_for_element("#upload-folder")
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# Verify the input has folder selection attributes when enable_folder_selection=True
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upload_input = dash_dcc.wait_for_element("#upload-folder input[type=file]")
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webkitdir_attr = upload_input.get_attribute("webkitdirectory")
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assert webkitdir_attr == "true", (
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f"webkitdirectory attribute should be 'true' when enable_folder_selection=True, "
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f"but got '{webkitdir_attr}'"
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)
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assert dash_dcc.get_logs() == [], "browser console should contain no error"
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def test_upfd002_multiple_files_without_folder_selection(dash_dcc):
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"""
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Test that multiple file upload does NOT enable folder selection
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when enable_folder_selection=False (default).
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"""
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app = Dash(__name__)
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app.layout = html.Div(
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[
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html.Div("Multiple Files Test", id="title"),
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dcc.Upload(
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id="upload-multiple",
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children=html.Div(["Drag and Drop or ", html.A("Select Multiple Files")]),
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style={
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"width": "100%",
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"height": "60px",
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"lineHeight": "60px",
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"borderWidth": "1px",
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"borderStyle": "dashed",
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"borderRadius": "5px",
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"textAlign": "center",
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},
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multiple=True, # Allows multiple files
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enable_folder_selection=False, # But NOT folder selection
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accept=".txt,.csv", # Accept should work with file picker
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),
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html.Div(id="output", children="Upload ready"),
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]
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)
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dash_dcc.start_server(app)
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# Wait for the component to render
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dash_dcc.wait_for_text_to_equal("#title", "Multiple Files Test")
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dash_dcc.wait_for_text_to_equal("#output", "Upload ready")
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# Verify the input does NOT have folder selection attributes
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upload_input = dash_dcc.wait_for_element("#upload-multiple input[type=file]")
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webkitdir_attr = upload_input.get_attribute("webkitdirectory")
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# webkitdirectory should not be set when enable_folder_selection=False
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assert webkitdir_attr in [None, "", "false"], (
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f"webkitdirectory attribute should not be 'true' when enable_folder_selection=False, "
111+
f"but got '{webkitdir_attr}'"
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)
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# Verify multiple attribute is set
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multiple_attr = upload_input.get_attribute("multiple")
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assert multiple_attr == "true", (
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f"multiple attribute should be 'true' when multiple=True, "
118+
f"but got '{multiple_attr}'"
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)
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assert dash_dcc.get_logs() == [], "browser console should contain no error"
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def test_upfd003_single_file_upload(dash_dcc):
125+
"""
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Test that single file upload does NOT enable folder selection.
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"""
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app = Dash(__name__)
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app.layout = html.Div(
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[
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html.Div("Single File Test", id="title"),
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dcc.Upload(
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id="upload-single",
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children=html.Div(["Drag and Drop or ", html.A("Select File")]),
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style={
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"width": "100%",
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"height": "60px",
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"lineHeight": "60px",
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"borderWidth": "1px",
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"borderStyle": "dashed",
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"borderRadius": "5px",
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"textAlign": "center",
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},
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multiple=False, # Single file only
146+
accept="application/pdf",
147+
),
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html.Div(id="output", children="Upload ready"),
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]
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)
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dash_dcc.start_server(app)
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# Wait for the component to render
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dash_dcc.wait_for_text_to_equal("#title", "Single File Test")
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dash_dcc.wait_for_text_to_equal("#output", "Upload ready")
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# Verify the input does NOT have folder selection attributes when multiple=False
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upload_input = dash_dcc.wait_for_element("#upload-single input[type=file]")
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webkitdir_attr = upload_input.get_attribute("webkitdirectory")
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# webkitdirectory should not be set when multiple=False
163+
assert webkitdir_attr in [None, "", "false"], (
164+
f"webkitdirectory attribute should not be 'true' when multiple=False, "
165+
f"but got '{webkitdir_attr}'"
166+
)
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168+
assert dash_dcc.get_logs() == [], "browser console should contain no error"

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