I have a similar bug at my job: Sometimes browsers delete our extension's database, or otherwise corrupt it. It's been an issue for years, but no one has been able to reproduce it. It's probably a 1 in 10 million bug.
I think it's a hardware bug. My "fix" was to backup a small, but key, part of the database to a separate storage mechanism browsers let us access. When the issue arises we can now try to detect the missing data and restore part of the db.
BUT! If this is actually a hardware bug, there is a chance that this additional database write will cause this big to occur even more often, as we now have to write to storage twice as often!
Are any of the bug reporters using Vivaldi? As for some reason that browser allows (and enables by default) clearing extension storage when clearing history/cookies via Delete Browsing Data.
This is something the Stylus addon dev noted when a user was reporting the addon wasn't remembering their settings and it was because the user had unwittingly wiped the extension storage due to the browser defaults.
(I actually use Vivaldi myself but virtually never use that feature so was unaware of the behavior until reading about the bug report)
No user that has reported it has been willing to share their database with us (chrome stores it in a standard leveldb), as it contains private information.
But good to know that about Vivaldi! I didn't know that before, thanks!
Even if the bug is fiendishly hard to track down and reproduce, you'd think there would be some additional safety checks they could add that would at least let it fail with an error message instead of actual data loss.
A better workaround would be to keep deleted emails around for some time so users have the option to restore them if the bug triggers. But this has drawbacks such as potential privacy breakage (you meant to delete mails you don't want the chance that anybody sees it) or free disk space management (your local drive is overloaded and you want to urgently free up space) or ux confusion (this is a de facto trash but Thunderbird already has such a feature)
Ultimately, what needs to be done is make the code robust, make sure there are no race conditions, etc.
Now even if we neglect the timeline, Rust only guarantees memory safety. If TB is deleting mails on the server too, then the corruption is happening over IMAP connections as well. Does that sound like a memory safety bug to you? Perhaps it is. But how do we eliminate the possibility of a logical bug that Rust won't protect you against, when nobody has any clue even now? And all that aside, if you're going to rewrite it in Rust, you might as well start a new project in Rust instead of porting an old design that may potentially contain a language-agnostic logical Heisenbug.
I'm not trying to be hostile here. I started using Rust in 2013 (I have 12 years of experience in a 10 year old language, and a bunch of repos that I can't compile anymore unless I compile the compiler from old commits somehow!). I wouldn't use C or C++ for any of these applications - I simply don't have enough competence to avoid the kind of bugs that Rust protects me from (despite being a hardware engineer with more knowledge about memory management than about type system theory). Despite all that, statements like this will only cause an unwanted backlash against Rust. Not that you're entirely wrong, but some people are so offended by such suggestions for reasons that are still under investigation, that they start a crusade against Rust [1].
I guess you'd disarm the person being facecious rather than the facetiousness, like you'd disarm someone about to cast you a magic spell.
No, you disarm the facetiousness, the same way you'd disarm a trap. Disarming the person wouldn't make sense.
https://en.wiktionary.org/wiki/disarm
> 2. (transitive) To deprive of the means or the disposition to harm; to render harmless or innocuous.
> [quotations] to disarm a man's wrath
My point wasn’t that this is a great solution, just that it is very easy and almost certainly better than doing nothing for almost two decades.
That's not what's happening. I wouldn't expect such an heuristic to be currently present. There is a bug, not something intentional.
> almost certainly better than doing nothing
No, because with such an heuristic, you add behavior that's difficult for the user to understand well and to work with. With such an heuristic, you will lose some mails and at some point the process stops in the middle. Which mails have you lost? What is "many" mails? 10? 100? What if my computer is fast and is deleting 100s of mails per seconds, losing all the mails anyway? What if it is slow and never triggers the heuristic?
If the heuristic does trigger, you end up with a mixed situation where you still have lost some stuff, but not all, and it'll be impossible to understand which ones. It doesn't fix the issue (you still lose email), just makes it even more difficult to understand even for the devs when they inevitable need to track down related issues. You really don't want to willingly add mechanisms that feel like they are non-deterministic: they are hard to debug, and hard for the users to grasp.
A way better solution is backups anyway: if you care not to lose your emails, you should be backing them up. From the beginning, your local TB mails are not a proper backup of your IMAP account because it's two-way synchronized so you need a backup somewhere else.
A still better workaround is disabling the move to local folder feature and make people copy and then manually delete mails.
Not saying your heuristic is not a good idea or clever (it is clever and could lead to further good ideas), just that after reflection, it should probably not be implemented. It barely starts to address the issue and adds complexity for everyone involved.
I don’t think LLMs are the answer to everything, but this would be a good test for newer generations of LLMs as they’re developed.
Worst case- it deletes all of your emails, but that would’ve happen anyway, right? =)
No, not at all. It's very easy.
This bug involves taking an inappropriate action under corrupted conditions. You don't need to know how those conditions arose. All you have to do is check whether they currently obtain, and - if so - refrain from taking the inappropriate action.
For this bug, that looks like this:
1. When we're executing a "move"...
2. Before deleting the original messages...
3. Check whether the copies are identical to the originals...
4. And if not, delete the copies instead of the originals.
At this point, the bug can't occur. The "root cause" bug, where your buggy logic says that you copied a bunch of messages even though you didn't, can still occur, but it can no longer delete any messages.
Literally nothing stopping anyone in this thread from opening a PR with this reportedly “very easy” fix that’s eluded developers for nearly two decades, and is so terrible folks swear off Thunderbird forever because I guess for email very basic rules for backing up data don’t apply (or something?) and/or Gmail and Outlook are implicitly trustworthy?
Nobody in the intervening nine years followed up by updating the bug's metadata, though. It's still "Windows XP only".
Well, this bug literally causes Thunderbird to delete your original copies of data during the backup process, so I'm not sure why backing up your data is supposed to be the solution.
If you're keeping backups of your disk, then this bug is not unrecoverable.
Hell, what if the offending commit was 2 decades ago by someone who's cut off all contact regarding code since?
the fact that they choose not to, makes me perfectly OK with them being held criminally liable.
And I know its not criminal, im saying it SHOULD be criminal not to warn people about this. its more than a decade
> Lets not warn anyone about that AT ALL, lets keep the feature activated and let them users lose their data
IDK why the assumption is that safety measures haven't been created. You wouldn't mark the bug as resolved if you put in safety features, right? You *ONLY MARK AS RESOLVED* after reproducing the bug and *VERIFYING* that it won't happen again. Right? Dear god I hope this is what you do, because otherwise you are prematurely closing bugs.
How can you possibly justify this behavior? I understand they dont owe the world any software, fine, but dont knowingly publish stuff that KILLS PEOPLES DATA without atleast a warning
> are you being for real?
> did you see anything as such in the bug listing?
> but even IF they did put safeguards in place, the fact that this is SEVENTEEN YEARS, no warning, functionality still enabled without ANY WARNING losing people data. unforgivable.
So let's consider a hypothetical situation. Suppose the problem was resolved in the almost 2 decades of rewriting BUT you still do not know what caused the bug in the first place and, consequently, can't reproduce it.
Do you mark the bug as resolved?
Now let's not sit in the hypothetical setting and act as developers. Some safeguards have been put in place (you can verify by looking at referenced issues). You've solved similar, but are unable to determine if these are the same problems or different problems (again, see referenced or use the search).
Do you mark the bug as resolved?
Your sibling commenter implied they would. Personally, I wouldn't. Marking as resolved is a promise to the user that it is fixed. But I can't make such a promise. I can't make any strong statement until I can reproduce. So yeah, it seems appropriate to me that it is marked as "unresolved" with steps "needs reproduction." That is an entirely appropriate status to me. You try as hard as you can and you implement as many safety features as you can, but you don't mark as resolved until you can verify. Unfortunately, this means issues go stale. Hell, there'll even be some noise like if a hacker or even just your dog deleted everything. We wouldn't want to assume the user is dumb and lull ourselves into a false sense of security, right? But you can only do so much.
*YOU CANNOT CLOSE A BUG REPORT IF YOU CANNOT VERIFY THE BUG*. That's the policy they are using. You may use a different policy, but that's the one they are using.
and then I would say: YOU DO NOT STOP WARNING PEOPLE UNLESS YOU CAN VERIFY ITS FIXED
(which ofc assume you bothered warning people to begin with)
> UNLESS YOU CAN VERIFY ITS FIXED
Yes?
Aren't we saying the same thing then?
We must be talking past one another. I'm (and others) are assuming they can't reproduce the bug. Assuming they aren't lying when they say so and assuming they've tried.
I mean let's take the trivial case. Assume user is dumb, deleted the files, made a bug report. Devs will never be able to reproduce unless user tells them they deleted everything 'on purpose'. That ends up with a permanently opened bug report no matter how much time you spend trying to fix the issue and no matter how many safety features you build in, right?
I am also saying that if they dont know for a fact its fixed, they should WARN PEOPLE IT MAY EAT DATA.
its 17 years!
I know people report the issue but googling I can find similar complaints across all major mail clients.
I just don't think there's enough information to make strong conclusions and I don't think California cancer warning labels work. I think they teach people to ignore warnings instead.
Looking at the timeline, it's possible that they've addressed a few of the bugs that result in data loss several years ago, and it's possible that the latest guy who ran into the problem within the last year triggered it in new ways or under new conditions but it's clear that the problem of thunderbird deleting messages from the server when copies haven't successfully been saved during a move operation wasn't solved by any "safety measures" 9 months ago and it's doubtful that it's been solved now.
My guess is that because thunderbird ultimately doesn't bother to make sure that messages are successfully and accurately copied before it removes them from the server it'll only be a matter of time before someone else stumbles on some other set of circumstances which results in data loss when messages are being moved.
> If they'd secretly implemented "safety measures" as you suggest that wouldn't be happening.
- Title: move/copying multiple imap messages to local folder bypasses offline store and redownloads messages. Need to preflight the move/copy.
Status: RESOLVED FIXED
https://bugzilla.mozilla.org/show_bug.cgi?id=505456
Which all I'm trying to argue is that they didn't just sit on their asses and do nothing for 17 years
>> Title: move/copying multiple imap messages to local folder bypasses offline store and redownloads messages. Need to preflight the move/copy.
>> Status: RESOLVED FIXED
This might be a more compelling observation if the bug was related to data loss. This just says "if you have a local copy of something, read from that instead of reading from the remote server".
It addresses the specific observation made in the thread that you can encounter the data loss bug even if you already have local copies of the messages, because Thunderbird ignores those, redownloads from the server, fails, and then deletes everything. Now, if you have local copies, Thunderbird won't try to redownload them from the server and the fact that the data loss bug isn't fixed won't matter to you.
You could apply this same approach to the entire bug, by guarding the "delete all of the user's emails" action instead of the "move emails that already exist locally" action. But they don't.
> it is almost impossible to fix a bug you can't reproduce
You could have fixed the bug (especially since a lot of TB was rewritten) but if you can't reproduce the bug you wouldn't know it was solved only that people stopped reporting it. This is actually a common occurrence with long standing bugs.
Yeah, reproducing is not theoretically mathematically necessary. In theory you could prove your code is correct with formal methods¹. Now, nobody does this because it is impractical (borderline impossible), reproducing is in practice so useful as to be almost essential:
- it lets you study how your code behave in the problematic case and identify what's causing the exact issue the user is seeing
- it lets you check that your fix does indeed address the bug
I have indeed already fixed trivial bugs without reproduction cases from a vague description of a bug because I'm intimately familiar with the code and it immediately rings a bell: the cause is immediately obvious. But that's not the usual case.
> the code can be changed to be more defensive and only ever delete the original when the new data has been successfully written and verified.
What if the code is already designed like this (and I sure do hope it is currently written like that, because that's almost common sense, if not the only sensible way of moving something) but somehow fails for some currently inexplicable reason? It smells race condition to me.
In the case of the discussed bug, users have described a reproduction case that's not 100%. But someone will need to find a 100% reproduction case. Users, or devs. It will not be optional. You can't play a guessing game, attempt to fix the code and hope for the best. You might be able to actually fix the bug, but without much confidence. Best case, you'll be able to find a reproduction case after fixing the bug (that you'll probably use as a functional test), to prove you fixed the bug for this specific case you found. You'll not be 100% sure you addressed the user's case.
A bug can hide another one, so you could find and fix a bug, but the issue is still present in the user's case. You can only be sure with their reproduction case.
But I agree that it is hard to reproduce a race condition.
¹ which in practice applies to code of trivial size (static analysis), or consists in checking a model but not the actual implementation (model checking), or does apply useful checks but is not exhaustive and has false positives / negatives (static analysis), or does apply useful exhaustive checks but only on a limited number of executions (runtime verification, and we do have functional tests that serve a similar purpose in practice - and you'll actually need the reproduction case here so you have the right execution to check), or requires you to write your code in a specific language (stuff like coq) and you cross your fingers that this specific language's implementation is itself correct. In short: not applicable here.
The problem is you can never close the bug report if you can't reproduce. I guess, you could, as the other commenter suggests, mathematically prove that it can't happen, but otherwise you're prematurely closing it.
How do you differentiate that you solved the bug and not a similar looking bug?
> the code can be changed to be more defensive and only ever delete the original when the new data has been successfully written and verified.
- What if it is an upstream issue? They have to be connected, since they are deleting data. Maybe it is completely a bug on their end? Doesn't matter how defensive you are if the bug was "anytime an email has 'man man' and is pulled between 00:00-00:04 everything deletes" then what can you do?
- What if the user was hacked and the hacker just deleted all the data?
- What if the user was just dumb and deleted the data themselves. Either not knowingly or were embarrassed to say anything.
- What if it is another program on the user's computer that is deleting the data because of some weird unexpected collision?
How do you close the report if you can not make strong guarantees that it is resolved?
It's a genuine question because I'm puzzled here.
A very small number of users have this bug (and tbf, it's a really bad bug), and are unable to consistently reproduce it and it seems none of the developers have been able to (the seemingly random nature of the bug occurring is not helping). How is it supposed to be fixed?
Said another way - If they can't reproduce it, they can't close it.
They may well have fixed it already, but without a way to reproduce it the only prudent behavior is to leave it open and wait for the next diagnostic file to be uploaded.
Now re-answer the above questions with these assumptions.
- How do you fix a bug you can't reproduce?
- How do you *close* a bug report when you can't reproduce?
Would some noble purpose be served by closing the existing issue in the hope that they'll complain via more official channels?
So yeah, I do think more user reports can help. At worse, it will make them take it more seriously if there are more reports.
You also are falling to observation bias. You can see linked in the issue as well as by searching that there are similar issues that were resolved and marked solved. So I don't think they were just doing nothing as everyone seems to be assuming.
> There's no sense keeping it open unless there are ongoing reports of the issue.
Let's consider this from a failure analysis standpoint. Here's our options
- You have incorrectly marked issue as solved
- You have incorrectly left the issue marked as unsolved
The classic example of this design choice is with a safe. Let's imagine you are building a safe. If the safe fails, would you prefer that it fails into a state that is unlocked or into a state that is locked? The answer isn't so obvious, as it actually depends on how it fails, right?
A very common example is when designing skyscrapers. The choice is that when a skyscraper fails, there is a strong preference that it falls in on itself (think 9/11). Why? Because if it falls to the side then it takes out other buildings and can create a chain reaction (a related famous example being housing in Industrial Revolution London and fire...)
Your action is a valid option, but it is not the option that I would chose. I think what they did was perfectly fine. They left it open (to avoid tricking anyone to thinking it is solved when the status of solved is actually unknown) and marked with additional information about lack of verification/reproducibility. Essentially, it is marked as stale.
So we're back to the earlier question:
- How do you *close* a bug report when you can't reproduce?
You strangle it from the edges.
- You can extend logging to gather additional information to reproduce it.
- You can try to reason about the code and figure out possible causes.
- You can attempt to formally verify the correctness of the code.
- You can put guards into the code against unexpected states and actions.
- You can verify the correct result of previous actions before any destructive actions.
- If all fails you can scrap the piece of code in question since it seems to be beyond your ability to maintain.
An acquaintance of mine were twice hit with a bug that corrupted Word documents stored on iCloud if editing on her iPad. Searching online yielded others with the same problem from more than one year ago...
> Being open or closed source has nothing to do with hearing about problems.
If my dad faced this issue, he'd never post online. He'd call me or go to a computer repair shop. That's what your average user will do.
Open Source users tend to be a bit more tech savvy. There's that famous article about Linux gamers reporting way more bugs than average users and how it can be accidentally misinterpreted as "why develop for linux?" These frequency biases are a big part of this. Pluus, OSS tends to do better bug tracking.
> you'd think there would be some additional safety checks they could add that would at least let it fail with an error message instead of actual data loss.
I think you've just made an assumption about a bug that was reported 17 years ago. Assuming nothing has been done since. It looks like they can't reproduce it, *making it impossible to mark as fixed* even if it was. But I wouldn't assume nothing was done.
Also remember that Gmail, Outlook, and others are in play here. They also maintain trashed items for 30 days, making it easy to recover. As the provider, they shouldn't make it easy to mass delete things either, right? TB is just the interface, frankly, I'm not sure I know how to permanently delete emails with it. I'm not sure I can. But the interaction here should result in multiple lines of defense.
Why I'm surprised is... well... this is HN. We know that a bug like this is very rare, right? I mean otherwise who would ever use TB, right? But if it's rare, it's really hard to track down. There years of comments without people including system information. The reproduction steps themselves are "sometimes." It's HN, so we can assume users here program, right? How would you solve this use?
FWIW, I've used TB on Linux and OSX for years and never faced an issue like this. The only one I've faced is sometimes not being able to connect to the server and having to resend an email.
On the other hand, when using Apple Mail:
- messages routinely doesn't show me messages I can see in TB.
- Frequently sending messages from my phone doesn't go through or ends up double sending.
- Searching will pull up emails from a year ago, prioritizing them over the email I got this week and was actually looking for (e.g. searching foo@bar.com).
- I can't even tag emails!?!?
- Do filters even work? Holy cow how do people live without filters!? How do you deal with spam? How do you deal with all those noisy needless messages and newsletter type of stuff that won't let you unsubscribe or comes from domains or addresses you can't block because emails you need come from the same addresses?
- It straight up renders PDFs inline with no warning, helping spammers.
- There's no folders and everything is just all jumbled together in a mess. How does anyone find anything?
I know these problems aren't on all platforms but TB IME has saved me a ton of time compared to using Gmail, Outlook, or Apple Mail. Hell, fucking Neomutt is a better experience than those three, which is insane. Trying to use them is like trying to use the internet without an ad blocker. How are we so bad at email?
When I updated the configuration in K-9, it contacted the fastmail server, found that the mail it had locally wasn't also present there, and immediately deleted all my local copies.
That's not a "bug" in the sense of unintended behavior of the software, but it certainly seems like the software designer's goal is to hurt the user. I obviously didn't want that to happen. There is no scenario where I would want that to happen.
Email clients make some strange assumptions about what kind of actions make sense under what conditions.
1. Copy from source to destination
2. Verify copy has completed without issue
3. Delete from source
but... some other way? So when you try to move from a server folder to a local client folder by an innocent looking drag an drop, combine this with a poor network connection, a garbage tier legacy protocol like IMAP and decade old C++ spaghetti code, and you get this textbook 17 year old severity 1 bug that will never get fixed.
(see https://bugzilla.mozilla.org/show_bug.cgi?id=462156#c69 )
Of course, it isn't; they're relying on an unstable proxy for "copy has completed without issue" in preference to just checking whether that happened or not. Several rather angry users have pointed this out. It doesn't seem to have sunk in.
I've so often had debates and threads in issues where a developer entrenched in a domain has so much domain-knowledge (ie. tunnel vision) that "technically correct" or "by the spec" is the only correct way. I've been that developer in many cases too, in hindsight.
Another example is HTTP Strict-Transport-Security which specifies that browsers should take control away from users.
It's another thing that got me interested in DDD. Where the user, domain, business and such define what things are called, how they operate, what events they undergo or emit etc. And not a spec, language or framework
And where e.g. "the IMAP spec" is a clear bounded domain, probably a service, an adapter or even library. Within that domain, "The Spec" dictates all the naming, conventions, logic etc, but where the border of this domain is another language. E.g. in a "MessageAdapterImap" something is called "EXPUNGE" with all the intricacies of what this means in IMAP. But in the outside it's e.g. part of a "cleanup()" interface, or whatever the domain calls it when it removes messages.
So if you want a mailbox sync tool, use a proper program for that like mbsync/isync. (But this can't cope with cross mailbox moves besides (not) propagating them.)
> How is it not top 1 priority to fix it?
Maybe because it is very rare? I have been using thunderbird for 10 years now on various OSes and never had issues.
I have no good alternative to thunderbird, it does so much of what I want. But this bug is awful.
As a software developer fixing stuff like this is only possible if you can reproduce it or otherwise get logs, telemetry and similar things, otherwise it is pretty much just guesswork.
Granted given the severity of the consequences I would've chosen a more defensive move-strategy (e.g. one that deletes mails only once they have been copied verifiably), but that would have significant performance impacts in the 99.99% of cases where it works, so finding the real problem is preferable.
The truth is that if this happens to you regularly, that you are probably the prime person to gather more data on this. Call it giving back to Open Source software.
Same but I never move my emails to local folders.
As a software developer you should be able to reason about your code and work backwards from the observed result to investigate possible causes.
When a plane crashes or bridge collapses the engineers tasked with finding the cause don't just throw up their hands if they can't make it happen again.
But OP said it also deletes the message in the server, so it may be a different bug, right?
Even if the software doesn't have known bugs, I do it if the data is important enough and especially if I were to not have a backup (for example, because the storage provider takes care of backups and redundancy. I personally like to have another copy that I manage myself, but how many people have their IMAP emails or Spotify playlist data backed up for example? I do, but not many people I think)
But this does seem to be a different issue from the one OP mentioned. Seems to be actually this one: https://connect.mozilla.org/t5/discussions/thunderbird-searc... (with suggested solution)
Emails to email client is an engine to the car. It is pointless without one and it is THE purpose of it. All the rest of functionality like fancy UI, filter, notifications, editor is meaningless if your emails were deleted without recovery. Even car without engine is more useful than email client with empty DB.
That said, even if the bug is impossible to isolate, it sounds like the chain of events that leads to it is known. They probably should disable the feature until someone is motivated to fix or replace the code. I'm sure that would anger a lot of people, but someone angry about the loss of a feature is probably better than someone who is angry at the loss of data. Especially given that the feature seems to be something someone would use to archive their mail.
I wont be using any email client that can break and delete all my emails from local and the server. Why would i? It may be a lottery but it isnt one i want to play.
The fact that they see this as low priority shows theyre morons.
Who would say 'yes please' to an email client that might permanently destroy some of your most important data at random?
Far too focused on the engineering POV than the optics and trust/reputation damage. My kind of moronic, but still moronic.
Apple's Mail app has had a virtually identical bug since Catalina; Michael Tsai's article on the issue currently has 636 comments:
https://mjtsai.com/blog/2019/10/11/mail-data-loss-in-macos-1...
After witnessing the bug myself, migrated to Thunderbird with Maildir enabled[1] for long-term storage; have yet to experience the issue despite a large database (>300,000 emails) and daily IMAP import to local folders.
[1] https://tinyapps.org/blog/202207100700_thunderbird_mbox_to_m...
It really is just bad rep and like the severity of this is pretty bad.
Email is a really critical protocol so even if this is happening to only some people, it should still be fixed asap.
What developers should do on such a critical and long standing issue is to offer an extension that victims can install to volunteer to track the bug. So they can click a button when things are fine to take a snapshot, and click another one when they encounter it.
I would install that and be part of the solution.
Whilst obviously not lethal, this Thunderbird bug sort of reminds me of the Therac-25 incidents in the 1980s. Very occasionally the machine would give patients massive overdoses of radiation. This bug wasn't easy to reproduce (thankfully) and turned out to be due to a race condition.
But of course, you can't find a problem if you don't investigate, and if it's a serious problem that's been documented then, as engineers, we can't just hide behind non-reproducibility as if it's some sort of magic shield. We have a responsibility to investigate and isolate the problem ourselves. If we don't do that we are effectively washing our hands of our own creations.
I've encountered several impossible to reproduced bugs in the past. And what I (or my team) would then do, is re-architecture (refactor) some pieces of software so that we could reproduce it. Like e.g. better logging, specialized layers/adapters/services, simpler logic, and -above all- better testability.
I've been amazed over the years this has never been fixed -- it's very hard not to make jokes about the standard lifestyle of open-source programmers, that they don't consider this a priority (note: that's a joke, I consider myself an open-source programmer. I would hope that's obvious, but someone just bothered to sent me a mean anonymous message)
One of my biggest bugbears with Microsoft Outlook has always been that its search function is terrible. If you can't find an email then it may as well not exist, and that's been a real problem on a regular basis during my career - particularly latterly when I was in leadership and necessarily lived in my email and calendar.
It's disappointing that Thunderbird has similar issues with such a fundamental function.
Perhaps there could be an option to disable stemming completely from the inverted index, which would be probably easier to implement than a post-search filter (which in itself doesn't sound very complicated..).
But of course, it's open source, anyone could contribute :D.
Not only is the UX a horror, its results rely on all sorts of technicalities. I, as a software engineer, can understand that a mail has to be downloaded in entirety locally in order to have it indexed and then show up in the results. And I understand that sub-sub directories aren't really a thing in IMAP, so searching this-dir-and-everything below is hard/impossible and so on.
But mostly the search algorithms are poor. So much so, that I often rely on (rip)grep to find mails. Or in a few occasions wrote a quick bash/python horror to push all my mail into a meilisearch instance and then use this search engine to get the lists and filters that I would expect thunderbird to have.
Yes. It's open source. So "go fix it" is a proper reply. But that doesn't make a complaint about the state of the search feature invalid.
Worse though, in Apple Mail I'll search an email address because I got an email earlier in the week and the first thing it'll show me is an email I got from that person 3 years ago with the correct result a few down. I really need a better email client for my phone...
1. Validate input, expect all external input (both human and machine generated) to be completely bogus.
2. Fail fast and early. If something seems off, crash straight away, and do not expect things to magically repair itself at a later stage.
3. Use pre- and post-conditions where appropriate.
I'm not sure about the exact definitions of defensive programming, but static type checking, and possibly unit testing, might also be part of it.
Imagine you're writing trading software, you have an algo go haywire and it machine guns the whole order book, and then you refuse to put a "max order size" outside of the algo to stop it from happening again because you can't figure out why it happened in the first place.
Try telling a regulator or your boss that was your reasoning.
Even if the bug can't be reproduced, on the basis of multiple user reports the first step absolutely should be to add some assertions and logging around email deletion.
The point is not to give it a "100% safe" label, the point is to start narrowing down possible root causes. If the problem recurs again, you'll have assertions ruling out certain possible culprit code paths as well as logs displaying the values of relevant variables.
The answer is that you keep working at it iteratively using a combination of logging, reporting, and defensive programming to systematically narrow down the possible causes. Sometimes you never arrive at a true root cause, but you get close enough that you can mitigate the problem and finally close the ticket out. At the end of the day, the customer/user doesn't care as long as it works.
However, what will really piss them off is telling them your hands are tied until they can reliably reproduce the issue for you. It's important they understand that you are working on it, and typically they will go out of their way to help solve the problem when they feel taken care of.
This happens more often, for example when many services work together in an asynchronous way, and in some very rare situation, unwanted behavior occurs. To fix that, it is often easier to reason through the entire process, and to identify weak spots. It might even be a good idea to switch to a different paradigm to avoid certain bugs altogether.
For this particular bug, I would start by reading a lot, and ensurong that the bug is indeed not easily reproducible (by trying to make it reproducible of course). If that fails, I would continue to think about root causes for the bug, and possible workarounds that would work in theory. Then I would try to estimate the amount of work required, and the risk of breaking other things, and report that to those who like to decide on further actions.
And of course, as I know very little about the inner workings of ThunderBird, I would simply ask ChatGPT o3 or similar for advice. It comes up with a plan that seems reasonable.
Sometimes, you can add some additional steps, logging, change behavior in corner case a bit, either to get more understanding next time it happens or even mitigate it. Sometimes, you have plenty of tools and ways to act. In my experience, that sometimes is basically always if one cares enough.
I'll keep using TB. I'll also make sure to look both ways when crossing streets and won't assume that cars are going to stop for red lights because my chance of getting hit crossing a street is more likely than getting hit by this bug.