Hello,

In the past hour, I did some research on authenticating by email and I
believe Django users would benefit a lot if email authentication was
included in contrib.auth .

Many people have been working on it, and the latest code I could find
is here: https://gist.github.com/586056. I am not a very good Googler,
so there may be better patches.

Anyway, there are several problems to solve besides this:
1. the default AuthenticationForm does not accept usernames longer
than 30 characters
2. UserCreationForm and possibly the UserChangeForm need to have Email
counterparts or become more flexible
3. User emails should be unique. My first thought is to add a unique
constraint depending on an optional AUTHENTICATE_BY_EMAIL setting
which defaults to False. I find this problem the hardest to solve.

I am really open to any suggestions, so please do.

Luke Plant, Julien Phalip, I know you have looked into this before and
I am really hoping you can share your thoughts as well.

----
https://gist.github.com/586056:

from django.contrib.auth.backends import ModelBackend
from django.contrib.auth.models import User

class EmailBackend(ModelBackend):

    def authenticate(self, **credentials):
        if 'username' in credentials:
            return super(EmailBackend,
self).authenticate(**credentials)

        try:
            user = User.objects.get(email=credentials.get('email'))
            if user.check_password(credentials.get('password')):
                return user
        except User.DoesNotExist:
            return None

For the record and as an answer to the previous question, I'd like to
quote Russell who wrote the following in reponse to a ticket of mine:

" The core-endorsed ticket for this problem is #3011. The patch on
that
 ticket isn't endorsed, but it points at the real problem - a need to
be
 able to specify a custom User model. There have been several
discussions
 directed at this problem, and I'm hoping to get a posse discussing
this at
 the upcoming DjangoCon sprints. If you want background on some
approaches
 that might work (and some that won't) search the archives for Lazy
Foreign
 Key. "

Thanks Russell and I wish you good luck in the Django sprints!

- Wim

On Aug 26, 5:23 pm, Wim Feijen <wimfei...@gmail.com> wrote:

"Django is a high-level Python Web framework that encourages rapid
development and clean, pragmatic design"—unless you want to do something
seemingly simple like using email addresses for authentication, in which
case you need to monkey patch models and forms to get everything working
right, which is neither rapid nor clean. What began as an innocuous feature
request five years ago is now a high-level, general purpose, abstract,
seemingly insurmountable design problem. The core developers are still
perfectionists, but they seem to have forgotten their deadlines.

Is there not a simple, pragmatic solution (optional and for new
installations—we're not talking about backwards compatibility here) that
could be implemented until the panacea of pluggable User models gets
figured out? Something as simple (albeit ugly) as wrapping new models and
forms in:

if settings.AUTH_EMAIL_AUTHENTICATION:

Should these things really take five years? What happened to pragmatic?

Clay

The major issue is that there is no way to do schema migrations in core (currently). So there's no way to handle increasing the length of the username field.  

More comprehensive solutions require more thought to figure out the pluggable User models.  

For the project I am working on, we solved this by making a custom
auth backend that checks the username against the email column.  We've
found it to be a nice clean solution to wanting to use email addresses
instead of usernames.

Sorry all, disregard my previous email, I misread one thing and
completely missed Wim's original message.

I don't understand what the "username" field length has to do with it.

And I think that's also the problem with Clay's original post:
Do you want to authenticate against email or also change the User model?

What if I want to authenticate against email but still have a username ("nick")?
Another setting?

An auth backend that checks against the email address (which is
already in the User model just like username) _is_ simple.
Rapid and simple would be to _ship_ such a backend in contrib.auth.backends.
Then it would really just be a single setting (AUTHENTICATION_BACKENDS
= ('django.contrib.auth.backends.EmailBackend',)).
The only thing left would be the label on the login template in my
naive understanding. (another one-liner I believe)

So I agree it would be nice and useful, but where's the monkeypatching.
If you want to authenticate against email _and_ take the "username"
out of the model, it's that second part that's the problem. That's
where I believe a set of settings and conditions is a kneejerk
workaround.

Cheers,
Danny

Hi,

Hell, not another ugly setting like this.

Should these things really take five years? What happened to pragmatic?

Yes, since no one needs it. Okay no one isn't true, but no one (for true
this time) who needed it stepped up and said "I'll implement it and see
that it ends up in trunk"

Regards,
Florian

It's the "required" of username that's the problem if you don't want a
username at all when authenticating against email.
It would have to be not required and check required fields in clean()
where the backend could be asked what's really required.
And there's Mr. Schema Migration again...

Cheers,
Danny

My django-email-login app (
https://bitbucket.org/tino/django-email-login/overview) does this by
putting a hash of the email adress in the username field. It isn't as nice
as it could be, but it works.

I would really like to see this solved another way, but it is a hard
problem with the current restrictions.

Tino

On Fri, Mar 9, 2012 at 3:23 AM, Danny Adair <danny.ad...@unfold.co.nz>wrote:

That's one problem. Another problem is that the default User.email field is
not unique, is not required, is not indexed, and may be too short.

And there's Mr. Schema Migration again...

Who's talking about a migration? I'm asking for something that will work
for *new* installations; existing installations can continue authenticating
against usernames  for all I care :)

Moreover, I'm thoroughly frustrated by the fact that developers *do* bring
working solutions to the table (in the form of patches in trac), but the
core developers won't integrate them, either because it's not the right
time (usually right before a release), because the patch isn't general
enough, or because the patch doesn't meet some absurdly high bar of
quality. I understand that they have a commitment to backwards
compatibility and that accepting a mediocre patch could mean maintaining it
for life, but I like to think that—with a framework that purports to be
"pragmatic"—there are pragmatic solutions to these problems—and not,
"sorry, it's not perfect, it can't go in."

The GSoC page (
https://code.djangoproject.com/wiki/SummerOfCode2011#Enhancedauth.user) is
a frustrating read. It goes on and on about how hard the problem is and how
wrong your solution is, but doesn't provide any detail as to why it's hard
or why it's wrong. Ticket #3011 was rejected without much of a reason. HM
asked for an explanation both in the ticket itself and on django-dev; no
explanation was ever given.

The GSoC page also mentions migrations:

"How can we roll out a new/modified User model without requiring almost
every Django application on the planet to undergo a complex database
modification?"

But again, why do existing databases have to change? We're talking about
leaving User as-is, by default, but providing a mechanism to use a
different model if the developer chooses. Clearly this is a decision the
developer would not take lightly: you're not going to change from username
authentication to email authentication without a bit of thought. Projects
that are using username authentication will continue to use username
authentication, but at least new projects that want/need email
authentication will be able to do that without monkey patching models.

The GSoC page also mentions Lazy Foreign Keys, but no explanation is given
there or in the linked django-dev thread as to why LFKs are required to
implement a pluggable User model. LFK may be the panacea of code
cleanliness and virtual awesomeness, but those of us with deadlines just
need to authenticate against email addresses, like, five years ago.

Cheers,

Clay

I'm sorry, that completely mis-characterises the situation. Lots of
people want this, but every single time this has been brought up since
I started using django (1.0), a core dev or BFDL has explicitly ruled
it out, saying "we cannot do this, requires schema migration, we'll
look at it for the next version".

At this point, the discussion is stopped. Once a proposal has the
smack down from a BFDL, what point is there trying to get it
integrated?

The next version comes, has it been addressed? No. Will it be
addressed in 1.4? No. Will it be addressed in 1.5? Possibly, but I
doubt it.

At $JOB we've given up waiting for some trivial changes, and have
simply patched django to not have these silly, arbitrary and incorrect
requirements¹ on email address and username.

We live in the real world, we have to be able to handle email
addresses that are of a valid length. We cannot tell a paying customer
"I'm sorry, your email address is too long, do you have one under 75
characters?"

It's a really invalid position to take, knowing something is broken
and incorrect, but not fixing it because 'change is hard'.

Cheers

Tom

¹ Here is my list of things that are broken with d.c.auth:

1) Length and character restrictions on username field. If I want to
use emails address as usernames, or usernames with spaces, the choices
made at lawrence.com 3+ years ago should not restrict me.
2) Email address fields must be large enough to hold valid email
addresses - that's 254 characters.

On 09/03/12 09:37, Clay McClure wrote:

What you are really saying is this: being pragmatic means that we
prioritise *your* immediate need above the need to keep the code and the
docs maintainable, and above the need to maintain compatibility with
existing installations.

There are a million-and-one hacks we would add if we took that approach,
and Django would have a million-and-one more bugs, or possibly much
worse - if you add just 10 boolean switches like the one you suggested
in an earlier email, you've got over 1000 combinations to test and
debug. The only way to avoid that in a framework like Django is well
defined APIs for components. No-one has brought such a thing to the
table and seen it through, that's why it hasn't come in.

I believe that all the problems you have can be solved already:

 - you can write your own authentication backend to authenticate
   by email

 - you can write your own login and account creation views

 - you can even override admin views by inserting items into
   urls.py

Yes, these are all more-or-less hacky. And they have problems. For
instance, what if you have two accounts with the same email address? (I
have that in some of my Django projects, BTW). The current code allows
it, so we can't change anything that would make it impossible, at either
the DB level or the Python level. This is the kind of issue that means
you can't just use the existing models.

A full and correct solution that didn't introduce dozens of new bugs is
quite hard - and I'm talking about just the code required to fix this
one feature for you, without doing anything more generally useful.

That is why we're not going to put hacks like this in core - we would
have to support these hacks for at least 3 versions if we did. We are
interested in *removing* existing hacks from our code base, and this is
vital if Django is going to see increases in features and functionality.
We are not interested in adding more hacks.

We also will refuse to litter our documentation with things like: "if
you've got this setting, it does this, otherwise you get this other
behaviour, and you've got to watch out for all these bugs because this
is a gross hack".

It does provide detail - it gives a list of issues you have to consider,
and tells you where to search for the other issues.

Some examples from a quick Google groups search for "auth User":

http://goo.gl/swTpr

http://goo.gl/fFlKh

These provide a lot of detail.

I don't know what thread you are talking about. Hanne Moa brings up the
subject here and gets two replies from Russell:

http://goo.gl/7p1JN

Regards,

Luke

--
"I imagine bugs and girls have a dim suspicion that nature played a
cruel trick on them, but they lack the intelligence to really
comprehend the magnitude of it." (Calvin and Hobbes)

Luke Plant || http://lukeplant.me.uk/

Even with these things, you are limited by the length of the username
field, the length of the email field, and the arbitrary restrictions
on what consists a username.

The length restrictions could be fixed straight away, and a note added
to the next relnotes informing users that the field has changed in
size. If they do not update their DB structure, then depending on the
database used, they will either get errors when a field value is
longer than the old limit, or silent truncation.

It's not ideal, but it doesn't cause any major problems for anyone who
reads the relnotes, and it will have to be done at some point anyway.
Even if Django did have schema migrations, the same behaviour would
occur for anyone who read the relnotes and did not apply the
migration, and many users with 'interesting' DB structures would not
be able to simply apply schema migrations either, so they would have
to do it by hand anyway.

It feels to me that only fear of change and how to manage that change
is what is stopping d.c.auth from being fixed.

Good for you! I don't see that as an issue. If you are using email
address as a unique name for identifying a user, we already have a
column for that, it's called username, and it has some of the right
semantics (unique, indexed field). It is the arbitrary length and
content restrictions that stop this from happening right now.

I don't see why wanting to use email address as the unique identifier
and username for a user requires any modification to the database,
apart from (as I keep repeating) removing the arbitrary length and
content restrictions on username.

I agree with this 100%. d.c.auth needs to be fixed, not have many
different settings that alter it's behaviour.

Cheers

Tom

On 09/03/12 14:49, Tom Evans wrote:

This is not true. There have been times when we have said we cannot
consider it right now, and that a solid proposal should be brought up at
the calls for proposals for 1.1/1.2/1.3 etc., or at other times when the
core developers can look at it.

And every time, the proposal has either been missing or simply not been
adequate - for example, the GSoC 2010 and 2011 proposals regarding this.
Russell gave detailed feedback on why these solutions were not adequate
[1], and at other times has provided feedback on possible strategies
[2]. And the people who went away to work on the problem have gone
silent or admitted defeat. One presumes they fixed their immediate
problem in a way that would not be a general solution, and moved on, and
that is perfectly understandable. A adequate solution to this is very
hard, and probably requires solving several other big problems first
(like at least one of lazy foreign keys/virtual models/database migrations).

It isn't, however, impossible. Our definition of 'need' is that someone
is sufficiently motivated to overcome the obstacles, and contribute a
solution that works for other people as well as themselves.

Regards,

Luke

[1] http://goo.gl/swTpr

[2] http://goo.gl/7p1JN

--

Luke Plant || http://lukeplant.me.uk/

I disagree. There are small problems with the User model that have not
been fixed. Every proposal you've listed does not address these
issues, but instead looks to find ways of replacing the base user
object, which is a complex and difficult project.

There is a reason why these are the proposals. Every time someone
proposes fixing these minor bugs, the cry from on high is that
instead, d.c.auth will be overhauled to allow for more customization
by the project, immediately increasing the scope and complexity. But
this fabled d.c.auth2 never appears.

In fact, your reply alludes to this. We're talking about why a field
is too short to contain valid values, and you suggest that the
solution inevitably will involve "lazy foreign keys/virtual
models/database migrations" - it's changing one line, and adding a
comment to relnotes!

We may have to agree to disagree on how easy some of these things are to fix.

Lets look at one isolated aspect. The User email field in d.c.auth is
too short. Emails can be up to 248 characters long, and d.c.auth only
allows 75.

Clearly, this is a bug, is wrong and should be fixed. How can we fix it?

We can alter the length of the field in the model definition. What
problems does this bring?

Users who do not manually update their database will not be able to
store longer length emails, and will get 'strange effects' when they
try - either silent truncation, or database integrity errors. How can
we mitigate this for users who refuse to update?

Provide a compat shim that resets the email length to that in 1.3, and
immediately mark it PendingDeprecation. Users who read the relnotes
and don't want to change their DB can use the shim, and have a clear
expectation of when they must have updated their database.

I still think these bug fixes are paralysed by a fear of change, and a
desire to engineer a solution that is every thing to every man. Lets
just fix these glaring bugs…

Cheers

Tom

While, I generally agree with the current approach, especially this close
to release. I'm going to play devil's advocate for a bit.

Schema migrations have been talked about for quite a while. There are at
least 3 external implementations I know of: South, nashvegas, and
django-evolution. I'm unsure of the status of django-evolution, but the
other two appear quite active.

A concern in my mind is that all three go off and do things totally
different ways, and the migration path to a common standard is more
difficult.

I love the idea of not choosing a tool to make the migrations, but instead
add to the ability to execute migrations. Now comes the conversation of
what that means. I would love to try to get this in to Django 1.5.

*Now on to the meat of what I really want:*
Is there something along the lines of the GNOME design group for Django?
(example: https://live.gnome.org/Design/Apps/Web). I'd love a template for
the wiki or even better an app to discuss these things. If only we had some
web developers ;) So, is there a sanctioned tool already out there? Or
should I start building up a page on the wiki for this? I think most things
become much easier once one gets a blueprint and requirements for what the
design goals are. Especially if one can get an initial "this looks
acceptable" by a core committer before "wasting one's time" because the
requirements weren't even correct.

Does github or bitbucket have such a feature I don't know about? Does
launchpad.net blueprints meet this? Is there some other place I don't know
about that someone could point me to?

--
Joe & Anne Tennies
tenn...@gmail.com

On 9 March 2012 17:46, Tom Evans <tevans...@googlemail.com> wrote:

The latest RFC[1] actually specifies this as 256 *octets* with max of
64 octets for the local part and 255 octets for the domain name. So
248 *characters* would actually be incorrect and all the tedious and
error prone fixing of every Django instance would just get wasted.

I don't really think this is a "fear of change" case. It's more of "we
don't want to have to fix this again" thing.

[1]: http://tools.ietf.org/html/rfc5321#section-4.5.3.1.1

--
Łukasz Rekucki

2012/3/9 Łukasz Rekucki <lreku...@gmail.com>:

Sorry, 248 was a typo. If you look at my earlier reply in this thread,
I had correctly stated the maximum length of an email address as 254
*characters*.

If you check two paragraphs later in the RFC that you linked to, you
would see confirmation of this:

http://tools.ietf.org/html/rfc5321#section-4.5.3.1.3

You may also need to remind yourself what the definition of a path is.

As all email headers are either 7 or 8 bit encodings, describing 254
octets as 254 characters is perfectly valid.

None of this changes that django keeps shipping with bad defaults.
This was brought up for 1.1, 1.2, 1.3 and now 1.4.

Cheers

Tom

On 9 March 2012 21:10, Tom Evans <tevans...@googlemail.com> wrote:

And RFC 3696 originally claimed it's 320. Even after errata it still
says 256, but you are right that 254 is probably more correct.

UTF-8 is an 8-bit encoding that doesn't map octets to characters, so
no. But that's not really the point I wanted to make.

My point is that this kind of things change and we should have tools
to deal with that. We already have the exact same problem with IPv6
and contrib.comments, it's just people didn't noticed it yet as much.
Doing this by hand every time isn't very effective. Django needs
schema migrations.

As for the "design page" that Joe mentioned, the GSOC description is a
good start:

https://code.djangoproject.com/wiki/SummerOfCode2012#Enhancedauth.user

--
Łukasz Rekucki

2012/3/10 Łukasz Rekucki <lreku...@gmail.com>

[...]

[...]

The tool for migration can be simple as docs/release note or release
warning :-) ?

We change the database schema and provide the SQL scripts to migrate the 4
supported backends (sqlite, mysql, postgres and oracle). This script are
needed "only" for upgrade projects, new projects it's just a normal path.

Is that hard, inconvenient or bad?

In my humble opinion it's simple and pragmatic.

[],
--
Luciano Pacheco
blog.lucmult.com.br

On 10/03/2012, at 1:52 AM, Joe & Anne Tennies wrote:

Django Evolution isn't dead. It's sleeping. It's got lovely plumage, you know... :-)

Seriously -- I stopped working on Evolution several years ago. I formally handed over the project to Christian Hammond almost 2 years ago, but this has been mostly for maintenance purposes, rather than active development. For the benefit of posterity, I blogged about the reasons [1].

[1] http://cecinestpasun.com/entries/end-my-evolution/

A lot of this conversation has already happened, and it has core team approval. Most of these discussions were elaborated in last year's aborted GSoC 2011 project; search the django-dev archives from this time last year to see the details of what was being proposed.

The short version:

 * Add a db.backends module to provide an abstract interface to migration primitives (add column, add index, rename column, rename table, and so on).

 * Add a contrib app that performs the high level accounting of "has migration X been applied", and management commands to "apply all outstanding migrations"

 * Provide an API that allows end users to define raw-SQL migrations, or native Python migrations using the backend primitives.

 * Leave the hard task of determining dependencies, introspection of database models and so on to the toolset contributed by the broader community.

Under this approach, South would still need to exist, but it would be a tool leveraging the primitives exposed by Django itself. Over time, more features from South (and any other migration support projects that emerge) could be merged into trunk as the community converged on a feature set or an implementation.

One of the big issues that needs to be addressed is testing -- we need to have the infrastructure that allows us to check that migrations have been applied. Arthur Koziel's AppRefactor (a GSoC 2010 project) has some analogous testing problems, so getting migrations into trunk may be dependent on getting the App Refactor into trunk as well. The good news is that the App Refactor also forms the likely stub for fixing the auth.User problem -- but that's a separate discussion.

There are some historical examples where we've used the wiki to elaborate on an idea as a precursor to getting a feature into core.

https://code.djangoproject.com/wiki/SessionMessages
https://code.djangoproject.com/wiki/ClassBasedViews
https://code.djangoproject.com/wiki/LoggingProposal
https://code.djangoproject.com/wiki/ReplacingGetAbsoluteUrl

(The first two are probably the best examples to follow)

There is a wiki page which has been used in the past to discuss schema evolution (which it looks like you've found); however, it's wandered a little off the reservation. There's probably some good material in there still, but if someone is looking at this, it would benefit from some manicuring, and probably a complete reboot:

https://code.djangoproject.com/wiki/SchemaEvolution

There isn't a specific wiki template that we require -- this is mostly because every project has slightly different requirements. However, the broad format is fairly common:

  * describe the problem
  * describe any specific design constraints
  * describe the possible approaches and their benefits/limitations
  * list any prior art
  * list any draft implementations

If you want to work on this, I can guarantee that you would have as much support as I and Andrew Godwin (South maintainer and Django core developer) can muster. This is one of the big ticket items missing from Django's core, and I'd *love* to see someone take a serious swing at addressing it. As with every big feature that is "missing" from Django (be it migrations, auth.User problems, or anything else), the issue is almost always finding someone who is willing to do the work -- not just for a day or two, but to actively drive a project for several months.

Yours,
Russ Magee %-)

What you are really saying is this: being pragmatic means that we

Of course not. Firstly, this is not *my* need; it's a feature that many
have requested. Take a survey of the web applications that you use on a
weekly basis. How many of them allow you to sign in with an email address?
Compared to that, how many required you to invent a username? Of those, I
would wager that a good many are Django apps.

Secondly, I'm advocating for a backwards-compatible solution that won't
break existing installations. That point keeps getting missed, as you and
others keep assuming that we need schema migrations for this change—we
don't. People who are happy with the existing user model can keep using it,
as-is. But people who aren't happy with it should be able to provide their
own.

I was giving an example of a pragmatic solution: sometimes an `if`
statement is better than a far-reaching architectural change. I don't
advocate boolean flags for solving the auth.User problem, I'm merely trying
to encourage a shift in thinking from lofty aspiration to humble
accomplishment.

True.

True.

True.

But these things aren't the problem. It's the auth.User model that poses
the challenge. If you haven't implemented email-based authentication in
your own apps, let me suggest that you try it before you tell me how easy
it is. At some point, you will run into these limitations posed by the User
model:

 - The username field can't be used to store emails (it's too short and
restrictive). No problem, let's use the email field;
 - But the username field is required. OK, we can just fill it with a
random string;
 - The email field does not have a unique constraint. But we can do a
reasonably good job applying the constraint in python;
 - The email field is not indexed. We don't want full table scans whenever
someone logs in, so let's write a custom (and possibly non-portable) SQL
migration to add an index.

All this, and the email field is still too short to hold all valid email
addresses. On top of that, we've littered our database and admin interface
with random strings for usernames, and littered our application with the
code to generate them.

Yes, these are all more-or-less hacky. And they have problems. For

Of course, which is why we need to allow developers to supply their own
User model, while maintaining backwards compatibility for those who are
happy with the built-in model.

A full and correct solution that didn't introduce dozens of new bugs is

Again, it's not just for me. And, yes, I appreciate that it's not a trivial
problem. It's hard, but all the problems worth solving are.

That is why we're not going to put hacks like this in core - we would

I can appreciate the appeal of a pristine, hack-free code base, but I've
never seen one. Eventually reality always trumps grand design. If my
example of the `if` statement above has led you to believe that I'm
proposing a mindless hack, then I apologize. I'm proposing something
between a mindless hack and grand design. Something pragmatic.

Some examples from a quick Google groups search for "auth User":

Some hand waving ("It's deceptively difficult"), with no examples, and no
mention of #3011.

http://goo.gl/fFlKh

This is someone with mediocre design skills trying to get paid to hack on
Django over the summer, but failing to convince anyone that he has a clue
about how to solve this problem. Save for some humorous jibes from Russell,
the thread is almost devoid of good content, except for Russell's example
of the COMMENTS_APP setting, which sounds a lot like "the idea of a
'pluggable' User model"—a proposal that the GSoC page indicates has already
been rejected, but without explanation.

I was thinking of this thread:

http://goo.gl/nehrO

wherein Carl Meyer (I confused CM with HM) enquires about #3011 and
receives no reply. In the thread you mention, there isn't any detail about
#3011, other than that the patch it contains is "*completely* the wrong
approach."

It poses a list of questions (how can we represent a generic user? how
should we approach authentication vs. authorization? how do we handle
migrations?) that all presuppose a grand redesign of auth.User instead of
an incremental improvement, but it doesn't discuss at all why an
incremental improvement won't be considered. And then it refers would-be
implementers to read up on Lazy Foreign Keys (LFKs), which I contend are
neither sufficient nor necessary for an auth.User refactor.

To illustrate this last point, consider some of the compatibility problems
we're liable to face when replacing django.contrib.auth.models.User:

1. Parts of Django, numerous third-party apps, and countless bespoke
software installations have models with FKs to User. LFKs could help here,
in that we could delay binding to the precise model until that binding is
known (through configuration, or whatever). But if, to use an LFK, any of
the third-party apps or bespoke software has to be changed (say, from
`ForeignKey(User)` to `LazyForeignKey('User')` or
`ForeignKey(LazyModel('User'))`), then LFKs are not backwards compatible.
They may be the place we want to end up, but they're not the place to
start, as they require too much change in software we don't control.

2. Parts of Django, numerous third-party apps, and countless bespoke
software installations have ModelForms built around the User model. The
model is specified in the ModelForm's Meta class, and must be available at
class definition time. LFKs don't help here. We could extend ModelForm to
support delayed binding, but if that involves changing any existing
software (say, `model = LazyModel('User')`), then, again, we've broken
backwards compatibility.

3. Parts of Django, numerous third-party apps, and countless bespoke
software installations import User from django.contrib.auth.models. But
we're talking about allowing developers to specify their own User model, so
code that imports d.c.a.m.User would no longer be valid. LFKs don't help
here, either.

What's needed is a way to maintain the interface defined by the existing
django.contrib.auth application (a User model in django.contrib.auth.models,
an AuthenticationForm in django.contrib.auth.forms, a ModelBackend in
django.contrib.auth.backends, etc) while allowing the developer to specify
the implementation—whether the stock User app, a reusable third-party app,
or their own.

I've written such a pluggable User app. By default, the User model works as
before. But I've also provided a User model (and forms, admin, backends,
etc) implementation that removes the limitations of the User model noted
above and allows for email authentication. It's still a bit rough around
the edges, but it works, insofar that `manage.py createsuperuser` doesn't
ask for a username, `manage.py changepassword` takes an email address, and
I can login to the admin interface with my email address.

It works for me, and that's well and good since I have a client that needs
this functionality, but I don't want to maintain the fork forever. I would
like to provide a patch for consideration for trunk, but before I waste my
time and yours, I'd like to understand why the notion of pluggable user
models was rejected (as indicated on the GSoC page), when Russell seems to
be advocating for a design of that sort with his reference to the
COMMENTS_APP setting.

And to be clear, I don't consider the pluggable user model approach that
I'm taking and the Lazy Foreign Key approach to be mutually exclusive.
Rather, I see my approach as something of a compatibility shim until
sufficient time has elapsed to pull the plug on imports of
django.contrib.auth.models.User. I ...

read more »

Can you please post this code somewhere? I'd love to see it.

Jacob

I started a new page off the old
https://code.djangoproject.com/wiki/SchemaEvolution (
https://code.djangoproject.com/wiki/SchemaEvolutionDesign). It's not
complete at this point, I just did a brain dump of what I remembered
hearing in the past. Sounds like I'm not TOO far off with my memory.

Also, is the following the thread you are thinking of?
http://groups.google.com/group/django-developers/browse_thread/thread...

Thanks in advance,
Joe Tennies

Also, Russell, I didn't know you were the one behind django-evolution. I
may need to pick your brain at some point. I have a couple ideas I'd like
input on, but I'm not quite ready yet. Now I wish I had tried harder to get
to PyCon this year, but work was supposed to be quite hectic this week.

My goal is to

On Sat, Mar 10, 2012 at 3:16 AM, Russell Keith-Magee <

--
Joe & Anne Tennies
tenn...@gmail.com