fix: keep line breaks and quoted text when printing a plain-text email

components/email/__tests__/viewer-print-plain-text.test.tsx

@@ -0,0 +1,94 @@
+// Printing a plain-text mail wrote its escaped text into the print window
+// with no white-space rule, so every line break collapsed into one run-on
+// paragraph, and a trailing ">" quote printed as the collapsed "•••" toggle
+// with the quoted text left out.
+import { fireEvent, render, screen } from '@testing-library/react';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import React from 'react';
+import type { Email, Mailbox } from '@/lib/jmap/types';
+
+vi.mock('@/hooks/use-media-query', () => ({
+  useDeviceDetection: () => ({ isMobile: false, isTablet: false, isDesktop: true }),
+  useMediaQuery: () => false,
+  useIsMobile: () => false,
+}));
+vi.mock('@/components/tour/tour-provider', () => ({
+  useTour: () => ({ activeTour: null, startTour: vi.fn(), endTour: vi.fn(), registerStep: vi.fn() }),
+}));
+
+class NoopResizeObserver {
+  observe() {}
+  unobserve() {}
+  disconnect() {}
+}
+vi.stubGlobal('ResizeObserver', NoopResizeObserver);
+
+const { EmailViewer } = await import('../email-viewer');
+
+const mailboxes = [
+  { id: 'inbox', name: 'Inbox', role: 'inbox', parentId: null, myRights: { mayAddItems: true } },
+] as unknown as Mailbox[];
+
+const TEXT = 'Hi Bob,\n\nline one\nline two\n\nOn Monday you wrote:\n> the old question\n> second quoted line\n';
+
+function plainMail(): Email {
+  return {
+    id: 'e1', blobId: 'b1', threadId: 't1', mailboxIds: { inbox: true }, keywords: { $seen: true },
+    from: [{ name: 'Alice', email: 'alice@example.com' }], to: [{ name: 'Bob', email: 'bob@example.com' }],
+    subject: 'Hello there', receivedAt: '2026-01-01T00:00:00Z', preview: 'Hi', hasAttachment: false, size: 100,
+    textBody: [{ partId: '1', type: 'text/plain' }], htmlBody: [{ partId: '1', type: 'text/plain' }], attachments: [],
+    bodyValues: { '1': { value: TEXT, isTruncated: false } },
+  } as unknown as Email;
+}
+
+function printToDocument() {
+  const popupDoc = document.implementation.createHTMLDocument('print');
+  let written = '';
+  const popup = {
+    opener: window as Window | null,
+    document: {
+      write: (html: string) => { written += html; },
+      close: () => { popupDoc.documentElement.innerHTML = written; },
+    },
+    focus: vi.fn(),
+    print: vi.fn(),
+  };
+  vi.spyOn(window, 'open').mockReturnValue(popup as unknown as Window);
+  render(<EmailViewer email={plainMail()} mailboxes={mailboxes} selectedMailbox="inbox" currentMailboxRole="inbox" />);
+  fireEvent.click(screen.getAllByTitle('print')[0]);
+  expect(popup.print).toHaveBeenCalled();
+  return popupDoc;
+}
+
+// The declarations of the print stylesheet's rules that apply to `el`.
+function appliedRules(doc: Document, el: Element): string {
+  const css = Array.from(doc.querySelectorAll('style')).map((s) => s.textContent ?? '').join('\n');
+  const rules = css.replace(/\/\*[\s\S]*?\*\//g, '').matchAll(/([^{}]+)\{([^{}]*)\}/g);
+  return Array.from(rules)
+    .filter(([, selector]) => {
+      try { return el.matches(selector.trim()); } catch { return false; }
+    })
+    .map(([, , body]) => body)
+    .join(';');
+}
+
+afterEach(() => vi.restoreAllMocks());
+
+describe('printing a plain-text email', () => {
+  it('keeps its line breaks', () => {
+    const doc = printToDocument();
+    const body = doc.querySelector('.body')!;
+
+    expect(body.textContent).toContain('line one\nline two');
+    expect(appliedRules(doc, body)).toMatch(/white-space:\s*pre-wrap/);
+  }, 30_000);
+
+  it('prints the trailing quote opened, without the toggle', () => {
+    const doc = printToDocument();
+    const details = doc.querySelector('.body details')!;
+
+    expect(details.hasAttribute('open')).toBe(true);
+    expect(details.textContent).toContain('> the old question');
+    expect(appliedRules(doc, details.querySelector('summary')!)).toMatch(/display:\s*none/);
+  }, 30_000);
+});

components/email/email-viewer.tsx

@@ -3651,9 +3651,12 @@ export function EmailViewer({
     // The body was sanitized with EMAIL_IFRAME_SANITIZE_CONFIG which permits
     // <style>. The print window has no iframe isolation, so re-sanitize with
     // the stricter config that forbids <style> before injecting into the DOM.
-    const printableBody = effectiveEmailContent.isHtml
-      ? sanitizeEmailHtml(effectiveEmailContent.html)
-      : effectiveEmailContent.html;
+    // A plain-text body is escaped text with its own newlines: it prints its
+    // trailing quote opened instead of behind the collapsed toggle.
+    const plainBody = !effectiveEmailContent.isHtml;
+    const printableBody = plainBody
+      ? effectiveEmailContent.html.replace(/<details>/g, '<details open>')
+      : sanitizeEmailHtml(effectiveEmailContent.html);
 
     const printWindow = openedWindow ?? window.open('', '_blank');
     if (!printWindow) return;
@@ -3678,6 +3681,9 @@ export function EmailViewer({
   .meta { font-size: 13px; color: #555; line-height: 1.6; }
   .meta strong { color: #000; }
   .body { font-size: 14px; line-height: 1.6; }
+  /* Plain text keeps its line breaks, as in the reader. */
+  .body.plain { white-space: pre-wrap; word-break: break-word; }
+  .body.plain summary { display: none !important; }
   /* Only force the cap on images that set no width of their own: an
      !important 100% also overrides a sender's inline max-width, and an
      image sized by max-width + max-height + width:100% then grows to
@@ -3699,7 +3705,7 @@ ${printWatermark ? printWatermark.html : ''}
     ${date ? `<div><strong>${escapeHtml(t('date'))}:</strong> ${escapeHtml(date)}</div>` : ''}
   </div>
 </div>
-<div class="body">${printableBody}</div>
+<div class="body${plainBody ? ' plain' : ''}">${printableBody}</div>
 </body></html>`);
     printWindow.document.close();
     printWindow.focus();