[Ur] Mandatory nginx conf: merge_slashes off

[Simon Van Casteren]

If it's not much work, I'd say yes. What I mentioned won't happen often,
but it was an extremely annoying thing to track down.

Simon

Op za 26 jan. 2019 om 19:33 schreef Adam Chlipala <adamc at csail.mit.edu>:

> Reviewing a PR just now, I'm reminded that the logic I half-recalled to
> avoid empty serializations is only for strings.  Would it be worth changing
> [unit] serialization to avoid empty serializations there, too?
>
> On 1/25/19 8:21 AM, Simon Van Casteren wrote:
>
> It doesn't happen often of course, since you rarely use unit in a page or
> RPC function. How I ran into it was actually via the now fixed bug
> https://github.com/urweb/urweb/issues/117, I made some ADT's that got
> around that bug by declaring all constructors to have at least one
> parameter, unit if nothing else. That came back to bite me now...
>
> A page with this signature:
>
> val page: unit -> string -> transaction page
>
> Would be affected by the issue I described. This obviously won't happen
> much outside of you making a mistake (for example because first the
> function took just a unit, then you added the string parameter), but
> because it doesn't happen often and it's actually nginx making the
> "mistake", I still thought it could help someone out in the future!
>
> Simon
>
> On Fri, 25 Jan 2019 at 13:57, Adam Chlipala <adamc at csail.mit.edu> wrote:
>
>> Thanks for sharing that wisdom!  Somehow I remember making a special
>> effort to encode empty strings with underscores, precisely to avoid this
>> problem (though it was appearing in Apache, if I recall correctly).  Can
>> you point us to an example where it arises, in a URL that an Ur/Web app
>> generates itself?
>>
>> On 1/25/19 5:13 AM, Simon Van Casteren wrote:
>>
>> Hi,
>>
>> I just ran into an awful problem combining urweb with nginx. By default,
>> nginx by default merges double slashes in urls, eg:
>> http://www.bla.com//users becomes http//www.bla.com/users. This can be a
>> problem for UrWeb applications since a double slash is actually how urweb
>> encodes the unit or () value.
>>
>> The solution is to use the option: "merge_slashes off".
>>
>> It's not a bug in either application so I didnt want me make an issue for
>> it, but this could be useful info for other people running Ur/Web programs
>> behind nginx...
>>
>> Simon
>>
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