feat: Add toggle for 3rd row message previews

[brmiller]

Summary

Per Issue #311 , add settings ability to disable message previews

Changes

Adds toggle to Settings | Appearance | Layout | Message List to disable message previews.

Testing

Included index.test.js (not sure if you do test files this way) to test local storage; live compile, re-deploy, re-run, manual testing of toggle on and off, displaying in different layout styles.

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  third-party material and confirmed it is compatible with the CLA).
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[brmiller]

Yes, I got excited and did not follow all the guidelines in the CONTRIBUTING.md. If you approve the idea of the issue, I will fix up my commit to use conventional commit style. I can also rename my branch if necessary.

[maathimself]

Thanks for this, two things currently fail the frontend test job (I ran npm test on the branch):

1. The store test fails. node --test on store/index.test.js throws ERR_IMPORT_ATTRIBUTE_MISSING for locales/en.json: importing the store transitively pulls in en.json, which Vite handles but raw node --test (what CI uses) rejects without a type: json attribute. That's why there's no existing store test. Please drop store/index.test.js, or, if you want coverage, extract the toggle logic into a small pure helper and test that instead of importing the whole store.

2. The new strings need every locale. The five new admin.messageList.* keys are only in en.json, which fails the existing i18n locale files test (it enforces key parity across locales) and leaves non-English users on English labels. Please add them to the other six (fr, es, it, de, ru, zh-CN).

With those two, npm test goes green. Two more for completeness:

3. Gate the expanded-thread previews too. There are three snippet renders in MessageList.jsx; the PR gates ThreadRow and MessageRow but not the expanded-thread sub-rows (the {msg.snippet || ''} near line 4135). With previews off, expanding a thread still shows a preview per sub-message. Please wrap that one in showMessagePreviews as well.

4. Persist the preference server-side. schedulePrefSave({ showMessagePreviews }) is sent, but PATCH /auth/preferences (backend/src/routes/auth.js) whitelists a fixed set of keys and doesn't include showMessagePreviews, so it's dropped: the toggle only lives in localStorage per device and won't sync across devices. Please add it alongside the sibling prefs (hoverQuickActions, showMobileAvatars) in that handler.

Appreciate you picking this up. Once those are in I'll re-review and get it merged.

[brmiller]

1. The store test fails. node --test on store/index.test.js... Please drop store/index.test.js...

Dropped.

2. The new strings need every locale. ... Please add them to the other six (fr, es, it, de, ru, zh-CN).

I am not a speaker of these languages. Rather than using a plain "google translate", I used an AI with some context of what I was doing and asked it to provide translations. Hopefully this is accurate. If not, let me know how I might get better translations.

3. Gate the expanded-thread previews too. There are three snippet renders in MessageList.jsx; the PR gates ThreadRow and MessageRow but not the expanded-thread sub-rows (the {msg.snippet || ''} near line 4135).

Good catch! I did not know this feature did that as I do not use it. :D Should be fixed.

4. Persist the preference server-side. schedulePrefSave({ showMessagePreviews }) is sent, but ... whitelists a fixed set of keys and doesn't include showMessagePreviews.

Added.

[maathimself]

Thanks! One thing before I can merge: the showMessagePreviews pref is read in auth.js but never written to the DB (it's missing from the UPDATE query and its params), so it won't persist or sync across devices. Can you wire it into the preferences UPDATE like the other prefs? Or if it's meant to be local-only, just drop the auth.js change. Thanks!

[brmiller]

@maathimself Take another look and thanks for your patience! I think I have the UPDATE statement updated now. I checked the database before and after multiple toggles, and it seems to be getting saved.

I also had a messy merge conflict because a) I had added showMessagePreview in the middle of some of the lists and b) some of the gravatar stuff has been removed from some of those lists. I ended up just re-adding the message preview methods names at the end of the lists which is possibly what I should have done from the beginning. So if you'll check I didn't actually remove something important, I'd appreciate it.

[brmiller]

Just a quick rebase - let me know if there's anything you'd like me to address!

[maathimself]

Thanks, the save side looks wired up right now.

One last thing and then I'll merge: it saves but never loads back. loadPreferences in store/index.js hydrates each pref from the server explicitly, one key at a time, and there's no block for showMessagePreviews. So on a second device (or after clearing localStorage) it falls back to the local default and the toggle doesn't actually sync. The GET returns the value fine, it's just never read into the store.

Mirror the showMobileAvatars block that's already in there:

if (typeof prefs.showMessagePreviews === 'boolean') {
localStorage.setItem('mailflow_show_message_previews', String(prefs.showMessagePreviews));
set({ showMessagePreviews: prefs.showMessagePreviews });
}

Drop that in next to the other avatar/favicon hydration blocks and it'll sync. Then it's good to merge.