fix: say in Composing that "Plain text only" also shows received mail as plain text

src/components/__tests__/plain-text-description.test.ts

@@ -0,0 +1,26 @@
+// "Plain text only" also makes the app show received mail as plain text
+// (plain-text-reading.test.ts), but Settings > Composing described it with
+// the webmail's text, which only talks about sending.
+import { describe, expect, it, vi } from 'vitest';
+import fs from 'node:fs';
+import path from 'node:path';
+
+vi.mock('expo-localization', () => ({ getLocales: () => [] }));
+
+import { translate } from '../../i18n';
+
+function description(rel: string): string {
+  const source = fs.readFileSync(path.resolve(__dirname, '..', rel), 'utf8');
+  const m = /t\('(settings\.email_behavior\.plain_text_mode\.[a-z_]+)', (['"])(.*?)\2\)/.exec(
+    source.slice(source.indexOf("plain_text_mode.label")),
+  );
+  if (!m) throw new Error(`no plain_text_mode description in ${rel}`);
+  return translate('en', m[1], m[3]);
+}
+
+describe('the plain text only setting', () => {
+  it('mentions reading in Composing as well as in Reading', () => {
+    expect(description('settings/ComposingSettings.tsx')).toMatch(/\bread\b/i);
+    expect(description('settings/ReadingSettings.tsx')).toMatch(/\bread\b/i);
+  });
+});

src/components/settings/ComposingSettings.tsx

@@ -133,7 +133,10 @@ export function ComposingSettings() {
 
       <SettingItem
         label={t('settings.email_behavior.plain_text_mode.label', "Plain Text Only")}
-        description={t('settings.email_behavior.plain_text_mode.description', "Disable the rich text editor and send all emails as plain text only, including replies and forwards")}
+        // The app also shows received mail as plain text with this on, which
+        // the webmail's description (sending only) leaves out; same text as
+        // under Reading.
+        description={t('settings.email_behavior.plain_text_mode.description_mobile', 'Compose and read in plain text only.')}
       >
         <ToggleSwitch checked={plainTextMode} onChange={(v) => updateSetting('plainTextMode', v)} />
       </SettingItem>