[Mailman-Developers] Discussion On Project Idea "Preset List Settings Templates" .

Sat Jan 30 17:46:46 EST 2016

On 01/30/2016 11:11 AM, Harshit Bansal wrote:
> Hi Steve,
> 
> On 1/27/16, Stephen J. Turnbull <stephen at xemacs.org> wrote:
>> Harshit Bansal writes:
>>
>>  > Figure out how to store and access the styles as some of them are
>>  > defined in the source code and the ones created by the by users would
>>  > have to be stored in databases?
>>
>> You also need a read/print repr.  A Python dict may be a reasonable
>> one, but JSON, YAML, init, etc could all be considered.
>>
> 
> I am planning to use dictionary.

What exactly I meant here was not a data structure but *how*? The data
structure could simply be dictionary, but how would you populate the
existing styles in the code? Notice that there is already an existing
IStyle interface in the mailman right now, can you modify it somehow to
dynamically update/fetch/store styles from the database instead of
creating a new structure altogether?

Barry: Is there a reason the styles in the src/styles/base.py are not an
implementation of IStyle interface?

If I am not wrong, you can define the styles in configuration too apart
from the source code, so how do you pull those and update the database
during the initialization?

This is not a difficult question I want an answer to right now, just
that the application should have implementation details too, even if
they are a rough sketch.
> 
>>  > Styles will be stored in database in a dedicated table.
>>
>> You may want more than one table.  Or you may be able to store them in
>> the same table as currently used for list configs, with that table
>> updated to allow "unstyled" as a value for its columns.  (List id,
>> for example, would be "unstyled", since it is supposed to be globally
>> unique.  Probably list name should be too, but domain would very
>> likely be styled.)
>>
>>  > The style manager will update all the styles 'predefined in the
>>  > source code' as well as the styles 'defined by users(by
>>  > implementing the IStyle interface)' to the database. Currently we
>>  > define a list of python import paths which are used for styles.
>>
>> Do you mean "configs"?
>>
>>  > These will be collected in the style manager and then updated in
>>  > the database. These styles will be publicly viewable but the users
>>  > wouldn't be able to modify/change them(using Postorius) otherwise
>>  > we would have to update those changes in the files as well.
>>
>> I don't understand why you wouldn't be able to modify them.  The
>> presets probably should be read-only, and you might want to have a
>> permissions system such that only the owner of the style can change
>> it.  Others would need to copy the style, modify the copy, and then
>> apply it to their own lists.
>>
> 
> Here, I meant to say that the 'predefined-styles' would be
> read-only(not modifiable) while the style defined by the user(using
> Postorius) would be readable/editable as per the permissions system.

You may want to expand more on the *permissions system* in you
application as that is an important part of this. Also, how are you
going to propagate that to the Postorius via the API.

> 
>>  > Should we even allow changing list styles after lists have been
>>  > created?
>>
>> Certainly.  Consider the case where a dramatic improvement in MUAs
>> commonly used by a subscriber base makes it possible to use Wrap
>> Message instead of Munge From as DMARC mitigation.  You want to change
>> all your lists in one go if they all have the same subscriber base
>> (consider an enterprise setting where the subscribers are mostly using
>> enterprise webmail).
>>
>>  > Does changing a list style in database/source code changes
>>  > the settings for list?
>>
>> IMO, yes.  But source code changes by the Mailman Project would not be
>> allowed, except with a looong deprecation/obsoletion cycle, and source
>> code changes should be documented as an operation with potential (bad)
>> surprises for users.
>>
>>  > I think there is no valid reason to not to allow changing list styles
>>  > after they have been created but there are two attributes about which
>>  > I am not sure these are:
>>  > 1: default_member_action
>>  > 2: default_nonmember_action
>>  > The value of these style attributes are first copied to
>>  > 'member.moderation_action'(moderation_action column of member table)
>>  > and then this saved value is used to decide the correct moderation
>>  > action. So changing the value of 'default_member_action' and
>>  > 'default_nonmember_action' have no effect on the saved values and
>>  > these will not change. This will have an undesired effect.
>>
>> I think that this is not a problem.  We need to initialize all
>> attributes to valid values, and this will probably be hard-coded in
>> the source.  Then we overlay this with site styles, domain styles,
>> list styles, and user attributes, and do the lookup in the opposite
>> order.  In principle, for each attribute you would drill down as long
>> as the value at the current level is "unstyled".  In practice, you'd
>> keep a cache of the current results of such lookups for users and
>> lists to avoid slamming the database, and some way of identifying when
>> the cache is out of date (such as a change "generation counter").
>> Note that this explains some of the reason why source code changes
>> need to be treated with care -- in some sense they are always
>> "generation 0" because it's impossible to know in advance what
>> generation the installlation is at.

I *think* we have had a discussion before about what should be a better
default value for member.moderation_action and
nonmeember.moderation_action. Instead of just copying them to the field,
we could set it to defer in which it case the lookup automatically picks
up the value of the list's default_(non)member_action.

Or we could *always* copy the default styles to a new style that the
list owner owns and can use for his other lists. This way he can change
values in the default styles too. This way, we don't have to deal with
user's being affected by the change in the default styles. Along with
that we could provide them with an option to update the styles
automatically from the default (when it changes) to fetch any new values
added/removed/updated. This however might introduce a *lot* of
redundancy in the database. Just a possibility, not very sure if this is
a good idea.

>>
>>  > So I think whenever a user changes these two attributes then we
>>  > will have to ask the user if he wants to change the saved values or
>>  > not. Another approach could be to leave these values unchanged and
>>  > bring this behavior to the knowledge of the user and if he wants
>>  > then he can manually change the moderation action of some selected
>>  > members but new members will automatically have their
>>  > moderation_action set to new the values.
>>
>> This is the current behavior for default_* actions; I don't see why it
>> would change with the introduction of styles.
>>
> 
> I wanted to ask that what should be the behavior when a user changes
> the 'default_member_action' and 'default_nonmember_action' attributes.
> Since, the values of these attributes are copied to the
> 'member.moderation_action' at the time of the creation of a new
> member. So, any changes made to the 'default_member_action' and
> 'default_nonmember_action' attributes will not be reflected in the
> already created members which I think may not be the desirable
> behavior.
> Please do correct me if am wrong somewhere.

See my comment above about the default behavior.

>>  > How to apply styles to lists after they have been created?  I will
>>  > expose the styles via REST API. Whenever the user(admin) will
>>  > change a mailing list's style in Postorius, it will automatically
>>  > call 'new_style.apply()' function which will update the mailinglist
>>  > table with the new values. This will change the list style.
>>
>> Be careful here.  Since some styles percolate up to user level, a site
>> with hundreds of thousands of lists and millions of users (they
>> exist!) could really slam the database.  The whole system would grind
>> to a halt.
>>
>>  > After implementing all these things, there will be two ways to create
>>  > and update styles :
>>  > 1: Using Postorius
>>  > 2: By defining a class implementing the IStyle interface and saving it
>>  > to a file.
>>
>> I don't see why you would allow 2 at all.  IStyle is an internal
>> thing, which would be used to provide a Python interface to the
>> database backend.  Unless you're thinking of dynamic styles (eg,
>> theming the list page according to day of week or server load :-)?
>>
> 
> Earlier, I was thinking to implement a way to add new styles using
> Postorius as well as by adding a file to the source code containing a
> class implementing the 'IStyle' interface to define the new style. But
> now I have dropped this idea as I think that it would not be that
> useful.

You cannot let users add stuff in the source code, configurations are
meant for the values that can be adjusted by users. AND you can add
styles via configs.

-- 
thanks,
Abhilash Raj

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