[web-devel] Kick-off discussion: Yesod 0.9

Michael Snoyman michael at snoyman.com
Wed Jun 1 17:46:49 CEST 2011

This is some good stuff, thanks. Some specific comments below.

On Wed, Jun 1, 2011 at 4:32 PM, Justin Greene <justin.j.greene at gmail.com> wrote:
>> * Forms package: It's been rewritten, but hasn't really had much input
>> from others. Now's the time to speak up if you have any opinions on
>> it. The code is available on Hackage.
> List of things that should be inside a forms package in my opinion.
> Custom Design: Form layout should be simple to customize and not be based
> around auto generating tables (if both are possible then of course the later
> can be used).

This is a major component of the design of the package. It now
supports both Applicative (auto generating tables/divs) and Monad
(custom layout) approaches. (The third type of form is an Input form,
intended for only receiving form submissions without generating HTML.)
Though I'm sure there are ways that the monadic forms could be
improved, given that they aren't used nearly as much as Applicative in
my sites.

> Variable length lists: It should be possible to add form elements on the
> client side and bind them on the server side.  An example of this would be a
> list of addresses.  A programmer should be able to add a new address widget
> client side without problems when binding server side.

Agreed, this needs to be added.

> Validation:  Complex validation scenarios should be simple and should fit
> into the normal validation pipeline.  An example would be validating that if
> a checkbox is selected then a textbox becomes required.
> All validation errors should display around the same time, e.g. if a type
> validator fires it should not prevent other validators from firing after it
> unless those validators depend upon that type data.

Right now, you can apply whatever validation you want to an individual
fields and display the error messages inline. For complex scenarios,
I'm not quite certain what an interface (both programming interface
and UI) would look like for assigning these error messages inline.
Short of that, it seems outside the scope of the form package itself
to validate such interactions. For example, you could always write
code along the lines of:

((res, form), enctype) <- runFormPost ...
case res of
    FormSuccess x ->
        case complexTest x of
            Left e -> showFormWithErrMsg form e
            Right y -> onSuccess y
    _ -> showFormWithoutErrMsg form

> These are just my thoughts based upon my experiences writing forms.  I can't
> really utilize any framework that doesn't implement these features for the
> types of projects I do.
> If you need any more details/clarification I'd be happy to help.

If you are interested in getting into more of the API design, that
would be awesome.


> On Mon, May 30, 2011 at 3:41 PM, Michael Snoyman <michael at snoyman.com>
> wrote:
>> Hi all,
>> It's been about a month since the 0.8 release of Yesod. In the release
>> announcement[1], we laid out some goals. Let's take a chance to
>> analyze where we're at:
>> * Documentation: Still improving as always. In particular, the new
>> Yesod site is making it much easier for me to write new content (I
>> have a few things on my local system that can finally go up).
>> * Static file caching headers: Implemented by Greg Weber. We'll likely
>> be making some API changes to handle embedded files, though that
>> discussion deserves its own blog post.
>> * Other template types: For Hamlet 0.9, we're going to be splitting
>> Julius/Coffeescript into their own package, and juggling the type
>> signature for Coffeescript a bit. At that point, it should be
>> straightforward to embed Coffeescript directly into a Yesod app, just
>> like Julius is today.
>> * Something like require.js: This is something we haven't started on
>> yet. I'll likely start looking into it this week. Additionally, I know
>> that a lot of my sites (jQuery powered) have numerous onload calls per
>> page; I think we can try to make that more efficient as well. I would
>> especially like people's input on this point.
>> * i18n: The solution is written, and I'm using it in production. At
>> this point, I'd call it beta quality, and I'd appreciate input.
>> * Embedded objects in MongoDB: No work done yet.
>> * Performance improvements: Nothing in particular. If you have any
>> examples of Yesod performing badly, please let us know.
>> The goal is for Yesod 0.9 to be feature complete, and for 1.0 to be a
>> fairly stable API. From the list above, my two priorities are better
>> Javascript loading (require.js) and static file serving. However,
>> there's one other major issue we need to address: the devel server.
>> Unfortunately, it doesn't work very well at all right now. Thankfully,
>> "yesod build" *does* work very well, and for my development I've
>> fallen back to simply "yesod build && ./dist/build/myapp/myapp" on the
>> command line. My guess is that we're 90% of the way there on "yesod
>> devel". This is a project that isn't tightly bound to the rest of the
>> API work, and would be very approachable for someone trying to get
>> started on Yesod development. If you're interested in helping out
>> here, please let me know.
>> I have no specific timeframe in mind for Yesod 0.9. As it stands now,
>> it looks like the 0.9 release will involve almost no API breakage,
>> which is a very good sign. But if you have any ideas you'd like to
>> contribute, I'd recommend getting them in in the next week or two.
>> Michael
>> [1] http://www.yesodweb.com/blog/2011/4/announcing-yesod-0-8
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