fix: Register default file action to prevent download instead of open

src/file-actions.js

@@ -2,13 +2,69 @@
  * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
-import { registerFileAction } from '@nextcloud/files'
+import { DefaultType, Permission, getFileActions, registerFileAction } from '@nextcloud/files'
 import { getCapabilities } from './services/capabilities.ts'
 import { translate as t } from '@nextcloud/l10n'
 
 // eslint-disable-next-line import/no-unresolved
 import appIcon from '../img/app.svg?raw'
 
+const supportedMimes = getCapabilities()?.mimetypes ?? []
+
+// Default file action for document types handled by richdocuments.
+// The Viewer app registers a generic 'view' file action that checks
+// window.OCA.Viewer.mimetypes, but those mimetypes are only populated
+// on DOMContentLoaded which can race with the file list rendering.
+// This action uses richdocuments' own capability list (available
+// immediately from OCS initial state) so it is not affected by timing.
+const openDocument = {
+	id: 'richdocuments-default',
+
+	displayName: () => {
+		return t('richdocuments',
+			'Open in {productName}',
+			{ productName: getCapabilities()?.productName ?? 'Nextcloud Office' })
+	},
+
+	iconSvgInline: () => {
+		return appIcon.replaceAll(/#(fff|0{6})/g, 'currentColor')
+	},
+
+	default: DefaultType.DEFAULT,
+
+	enabled: ({ nodes }) => {
+		if (nodes.length !== 1) {
+			return false
+		}
+		const node = nodes[0]
+		if (!node.isDavResource || !node.root?.startsWith('/files')) {
+			return false
+		}
+		if (!(node.permissions & Permission.READ)) {
+			return false
+		}
+		return supportedMimes.includes(node.mime)
+	},
+
+	exec: async ({ nodes, view, folder }) => {
+		// Delegate to the Viewer's own 'view' action when available
+		// so that URL history and prev/next navigation work correctly.
+		const viewAction = getFileActions().find(a => a.id === 'view')
+		if (viewAction?.exec) {
+			return viewAction.exec({ nodes, view, folder })
+		}
+
+		// Fallback: open directly through the Viewer API
+		if (window.OCA?.Viewer) {
+			window.OCA.Viewer.open({ path: nodes[0].path })
+			return null
+		}
+		return false
+	},
+}
+
+registerFileAction(openDocument)
+
 const openPdf = {
 	id: 'office-open-pdf',