Why don't we just turn off MOZ_BLOCK_PROFILE_DOWNGRADE?

Mark Banner mbanner at mozilla.com
Fri Jul 5 08:39:37 UTC 2019

On 04/07/2019 23:27, Matt Harris wrote:

>> The feature was created on the premise that internal data storage (db 
>> such) doesn't work well with downgrading, when the database structure 
>> changed. Since there is no backward compat promise of any sort, but 
>> rather the opposite, I'm also concerned downgrade attempts would 
>> increasingly mess up your profile data.
> I am concerned that what I consider the purist view. The new version 
> is a must for the user and they must be forced down this path with no 
> way to opt out is simply alienating users.  WE tell them their add-ons 
> do not work with this version and are disabled.

Firefox has already solved this issue with WebExtensions. Thunderbird is 
obviously working towards WebExtensions, but maybe there's other ways 
Thunderbird could manage this (like checking before updating).

> Do we offer an alternative,  like stay where you are for a month and 
> see if that changes.  No,  we force an upgrade that the user then 
> immediately starts trying to downgrade because the upgrade turned out 
> to not be an improvement.  Support forums are full of the term "roll 
> back" and given the ability to do so with windows operating systems 
> upgrades for the last decade,  we are not meeting user expectations at 
> all in not offering to do it for them, 

I think that's really something that's legacy. These days, I would say 
that we generally recommend staying with the latest supported version(s) 
because of all the security fixes. For Firefox that's probably something 
more significant that Thunderbird.

Yes, occasionally things might break, but then we generally do our best 
to get them fixed, rather than having users sticking on an old version.

> However Mozilla have taken the exact reverse position, they have gone 
> out of their way to make it hard.  This a simply a bad decision.  As 
> Mark Banner pointed out it has benefits in simplifying the lives of 
> developers,  but I have not yet seen a single user facing benefit. 
> There is the intangible "it is safe" approaches. 

There probably isn't a direct user benefit. There's various indirect 
ones which are just as good as direct ones: Preventing downgrades 
prevents more issues as a result of the downgrade; being able to change 
profile structures without backwards compact means faster development 
and improvements for users (including better performance which is often 
profile related).


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