David,
sounds reasonable.
So being able to call prepend/append after boot() makes no sense.
In the light of htis, it shouldn't be possible to call the prepend/append
outside of boot.
I suggest my approach described previously. (Injecting an initialization
context into boot and use that to configure LiftRules, then we don't expose
the mutativity in LiftRules.
Result: No runtime exceptions, no confusion on when to configure the webapp
etc.
Input?
Cheers,
Viktor
On Sun, Dec 14, 2008 at 3:41 PM, David Pollak <feeder.of.the.be...@gmail.com
> wrote:
> Folks,
>
> I have not had a single instance of wanting to change global application
> behavior at runtime. I cannot think of use case for such a feature.
>
> On the other hand, the idea that your program behavior is stable from the
> first HTTP request on makes a lot of sense to me. It means tests work
> because the tests don't have to worry about the behavior of the program
> changing. The same n steps will lead to the same result.
>
> If anyone can come up with a use case for globally changing program
> behavior during program execution, I'm all ears, but barring that, once the
> boot phase is over, the stuff in LiftRules should be frozen.
>
> Thanks,
>
> David
>
>
>
> On Sun, Dec 14, 2008 at 3:54 AM, Marius <marius.dan...@gmail.com> wrote:
>
>>
>>
>>
>> On Dec 14, 12:53 pm, "Viktor Klang" <viktor.kl...@gmail.com> wrote:
>> > On Sun, Dec 14, 2008 at 11:42 AM, Marius <marius.dan...@gmail.com>
>> wrote:
>> >
>> > > On Dec 14, 12:10 pm, "Viktor Klang" <viktor.kl...@gmail.com> wrote:
>> > > > On Sun, Dec 14, 2008 at 9:28 AM, Marius <marius.dan...@gmail.com>
>> wrote:
>> >
>> > > > > On Dec 14, 3:02 am, "Jorge Ortiz" <jorge.or...@gmail.com> wrote:
>> > > > > > Not to beat a dead horse, but... what's the rationale, again,
>> for
>> > > > > throwing
>> > > > > > an exception after boot? Is there a real danger to some or all
>> > > RulesSeqs
>> > > > > > being mutable after boot? If some, then those rules should
>> > > selectively be
>> > > > > > protected. Even if they're all dangerous, there are better
>> (i.e.,
>> > > type
>> > > > > safe)
>> > > > > > ways of protecting RulesSeqs from mutation than just throwing an
>> > > > > exception.
>> >
>> > > > > This was actually DPP's suggestion. I'm not sure why would someone
>> > > > > mutate them after boot but I'm totally opened if there is a strong
>> > > > > case for allowing that. I do not have strong feelings about this
>> so
>> > > > > changing it would be trivial. Still I kind of like it this way.
>> What
>> > > > > other ways of protecting mutations after boot are you referring?
>> ...
>> > > > > something like ignore it and do nothing?
>> >
>> > > > Hmm, how about "locking" them by havign a paralell lazy val?
>> >
>> > > > val somePf : RuleSeq = Nil;
>> >
>> > > > lazy val runtimeSomePf = somePf.toList
>> >
>> > > > Then prepending/appending on the somePf AFTER runtimeSomePf has been
>> > > > dereferenced won't make a difference.
>> > > > (runtimeSomePf would be used by Lift internally if that isn't clear
>> > > enough
>> > > > :) )
>> >
>> > > Still we'd allow useless strong references on those lists.
>> >
>> > > > Or another, perhaps more suitable suggestion:
>> >
>> > > > make boot() have an InitializationContext parameter that's only
>> available
>> > > in
>> > > > the scope of boot, and then the problem should disappear?
>> >
>> > > How would the problem disappear? ... I mean after boot people would
>> > > still be able to add their functions (from API perspective) and they
>> > > would be surprised that their functions are not called and yet lift
>> > > just allowed them to do that.
>> >
>> > I meant something like:
>> >
>> > def boot(val lc : LiftContext) =
>> > {
>> > //prepend/append,configure everything on lc
>> >
>> > }
>> >
>> > And then when the LiftFilter runt boot:
>> >
>> > {
>> > val lc = LiftContext(/*servletContext and stuff goes here*/)
>> > boot(lc)
>> > LiftRules.init(lc)
>> >
>> > }
>> >
>> > And then only have non-append/prependable stuff in LiftRules?
>> >
>> > But really, what is it a problem that lift is reconfigurable during
>> runtime?
>> > I thought that was kind of cool?
>>
>> As I said I don't have strong opinions on this. It was DPP's
>> suggestion and personally I kind of like it which does not mean that
>> things can not change :) ... AFAIC reconfiguration at runtime does not
>> make a whole lot of sense because:
>>
>> 1. We'd have to expose other functions to allow people to also remove
>> their function not only prepend & append them
>> 2. I do not see what kinds of problems runtime reconfiguration really
>> solve (I'm only referring on the current RulesSeq members). I haven't
>> encounter a practical need but if you have please let me know.
>> 3. Dynamic behavior can happen inside user's functions without
>> allowing runtime reconfiguration.
>>
>> Just my 2 cents ...
>>
>> P.S.
>> If the general consensus is to remove this restriction I have no
>> problem removing it ... so more thoughts/perspectives on this are
>> welcomed.
>>
>>
>>
>> >
>> > Cheers,
>> > Viktor
>> >
>> >
>> >
>> >
>> >
>> > > > Cheers,
>> > > > Viktor
>> >
>> > > > > > Nit-pick: why is 'toList' (which just returns 'rules') defined
>> as
>> > > > > > private[http] when 'rules' itself is public?
>> >
>> > > > > Why would you use toList in the lift app code? ...RulesSeq is
>> mainly
>> > > > > about adding user functions to lift. If "rules" itself is public
>> > > > > doesn't necessary mean that it should not have its "private"
>> logic.
>> >
>> > > > > > Also, if RulesSeq are always made up of either Functions or
>> > > > > > PartialFunctions, maybe we should enforce that at a type level,
>> and
>> > > the
>> > > > > > helper methods on Seqs of PFs that now exist in the NamedPF
>> object
>> > > can be
>> > > > > > put in the RulesSeq object.
>> >
>> > > > > But what would be the benefit? .. except that it would simplify a
>> bit
>> > > > > how Lift calls these PF's?
>> >
>> > > > > ... to me distinguishing between functions and partial functions
>> here
>> > > > > by using Either or even using different RulesSeq traits would not
>> > > > > bring much benefits ... but I hope I'm wrong.
>> >
>> > > > > > --j
>> >
>> > > > > > On Sat, Dec 13, 2008 at 2:31 PM, Marius <
>> marius.dan...@gmail.com>
>> > > wrote:
>> >
>> > > > > > > All,
>> >
>> > > > > > > I committed a bunch of changes in LiftRules. In a previous
>> thread
>> > > > > > > Jorge suggested the abstraction of LiftRules variables. Lists
>> of
>> > > > > > > functions are now abstracted by RulesSeq trait, which contains
>> > > prepend
>> > > > > > > and append functions. Note that if you're calling
>> prepend/append
>> > > > > > > functions after boot they will throw an exception. If there
>> are
>> > > > > > > compelling reasons not to do this please let us know. This is
>> just
>> > > a
>> > > > > > > mechanism to enforce the use of these functions on startup.
>> >
>> > > > > > > Br's,
>> > > > > > > Marius
>> >
>> > > > --
>> > > > Viktor Klang
>> > > > Senior Systems Analyst
>> >
>> > --
>> > Viktor Klang
>> > Senior Systems Analyst
>>
>>
>
>
> --
> Lift, the simply functional web framework http://liftweb.net
> Collaborative Task Management http://much4.us
> Follow me: http://twitter.com/dpp
> Git some: http://github.com/dpp
>
>
> >
>
--
Viktor Klang
Senior Systems Analyst
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