@ckeditor/ckeditor5-paste-from-office/src/filters/replacetabswithinprewithspaces.js

Paste from Office feature for CKEditor 5.

/**
 * @license Copyright (c) 2003-2026, CKSource Holding sp. z o.o. All rights reserved.
 * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-licensing-options
 */
/**
 * Replaces tab characters with spaces in text nodes that are inside elements styled with `white-space: pre-wrap`.
 *
 * This is a workaround for incorrect detection of pre-like formatting in the DOM converter for pasted Google Docs documents.
 * When an element uses `white-space: pre-wrap`, the editor reduces tab characters to a single space, causing
 * inconsistent spacing in pasted content. This function replaces tabs with spaces to ensure visual consistency.
 * This is intended as a temporary solution.
 *
 * See: https://github.com/ckeditor/ckeditor5/issues/18995
 *
 * @param documentFragment The `data.content` element obtained from the clipboard.
 * @param writer The upcast writer used to manipulate the view structure.
 * @param tabWidth The number of spaces to replace each tab with. Defaults to 8.
 * @internal
 */
export function replaceTabsWithinPreWithSpaces(documentFragment, writer, tabWidth) {
    // Collect all text nodes with tabs that are inside pre-wrap elements.
    const textNodesToReplace = new Set();
    for (const child of writer.createRangeIn(documentFragment).getItems()) {
        if (!child.is('view:$textProxy') || !child.data.includes('\t')) {
            continue;
        }
        // Check if any parent has `white-space: pre-wrap`.
        if (hasPreWrapParent(child.parent)) {
            textNodesToReplace.add(child.textNode);
        }
    }
    // Replace tabs in each collected text node.
    for (const textNode of textNodesToReplace) {
        replaceTabsInTextNode(textNode, writer, tabWidth);
    }
}
/**
 * Checks if element or any of its parents has `white-space: pre-wrap` style.
 */
function hasPreWrapParent(element) {
    let parent = element;
    while (parent) {
        if (parent.is('element')) {
            const whiteSpace = parent.getStyle?.('white-space');
            if (whiteSpace === 'pre-wrap') {
                return true;
            }
        }
        parent = parent.parent;
    }
    return false;
}
/**
 * Replaces all tabs with spaces in the given text node.
 */
function replaceTabsInTextNode(textNode, writer, tabWidth) {
    const { parent, data } = textNode;
    const replacedData = data.replaceAll('\t', ' '.repeat(tabWidth));
    const index = parent.getChildIndex(textNode);
    // Remove old node and insert new one with replaced tabs.
    writer.remove(textNode);
    writer.insertChild(index, writer.createText(replacedData), parent);
}