fix: show a single duplicate-name error during file creation

apps/files/src/components/NewNodeDialog.spec.ts

@@ -0,0 +1,65 @@
+/*!
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { cleanup, fireEvent, render } from '@testing-library/vue'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import NewNodeDialog from './NewNodeDialog.vue'
+
+describe('NewNodeDialog', () => {
+	afterEach(cleanup)
+
+	it('shows a single inline error for a duplicate name without reporting native validity', async () => {
+		const component = render(NewNodeDialog, {
+			props: {
+				otherNames: ['existing.txt'],
+			},
+		})
+		const input = component.getByRole('textbox', { name: 'Folder name' }) as HTMLInputElement
+		const reportValidity = vi.spyOn(input, 'reportValidity')
+		const setCustomValidity = vi.spyOn(input, 'setCustomValidity')
+
+		await fireEvent.update(input, 'existing.txt')
+
+		expect(component.getAllByText('This name is already in use.')).toHaveLength(1)
+		expect(component.getByRole('button', { name: 'Create' })).toBeDisabled()
+		expect(setCustomValidity).toHaveBeenLastCalledWith('This name is already in use.')
+		expect(input.validity.valid).toBe(false)
+		expect(input.validationMessage).toBe('This name is already in use.')
+		expect(reportValidity).not.toHaveBeenCalled()
+	})
+
+	it('clears inline and native validity when the name becomes unique', async () => {
+		const component = render(NewNodeDialog, {
+			props: {
+				otherNames: ['existing.txt'],
+			},
+		})
+		const input = component.getByRole('textbox', { name: 'Folder name' }) as HTMLInputElement
+
+		await fireEvent.update(input, 'existing.txt')
+		expect(input.validationMessage).toBe('This name is already in use.')
+
+		await fireEvent.update(input, 'unique.txt')
+
+		expect(component.queryByText('This name is already in use.')).not.toBeInTheDocument()
+		expect(input.validity.valid).toBe(true)
+		expect(input.validationMessage).toBe('')
+		expect(component.getByRole('button', { name: 'Create' })).toBeEnabled()
+	})
+
+	it('shows other filename errors inline without reporting native validity', async () => {
+		const component = render(NewNodeDialog)
+		const input = component.getByRole('textbox', { name: 'Folder name' }) as HTMLInputElement
+		const reportValidity = vi.spyOn(input, 'reportValidity')
+
+		await fireEvent.update(input, '')
+
+		expect(component.getAllByText('Filename must not be empty.')).toHaveLength(1)
+		expect(component.getByRole('button', { name: 'Create' })).toBeDisabled()
+		expect(input.validity.valid).toBe(false)
+		expect(input.validationMessage).toBe('Filename must not be empty.')
+		expect(reportValidity).not.toHaveBeenCalled()
+	})
+})

apps/files/src/components/NewNodeDialog.vue

@@ -147,7 +147,6 @@ watchEffect(() => {
 	const input = nameInput.value?.$el.querySelector('input')
 	if (input) {
 		input.setCustomValidity(validity.value)
-		input.reportValidity()
 	}
 })