[web-devel] Re: Proposed changes to web-routes: query-string support

[Jeremy Shaw]

Hello,

There are a few concerns I have with the patch so far:

 1. When a form uses method="GET", the searchpart (query string) of
the action is ignored. For example, if you do:

    <form action="/get?foo=bar" method="GET">...</form>

 The, foo=bar, will not appear in the query string when the form is
submitted.  I guess there is really nothing we can do about this
except document the fact that you shouldn't do that..

 2. I think the encodeUrlChar function is too aggressive. It seems to
encode all reserved characters, not just the ones that have special
meaning?

 "Reserved characters are those characters that *sometimes* have
special meaning"

 "The sets of reserved and unreserved characters and the circumstances
under which certain reserved characters have special meaning have
changed slightly with each revision of specifications that govern URIs
and URI schemes."

 "When a character from the reserved set (a "reserved character") has
special meaning (a "reserved purpose") in a certain context, and a URI
scheme says that it is necessary to use that character for some other
purpose, then the character must be percent-encoded."

 I believe that :@$, do not need to be encoded in the query string?

3. integration with other parts of web-routes

 It looks like your patch handles integration with things like RouteT
by simply hardcoding the query parameters to the empty list. If we are
going to add support for this, then it would be nice if it was
actually usable everywhere. I will see what happens when I try to add
support I guess.

- jeremy

On Sun, Aug 8, 2010 at 7:03 AM, Michael Snoyman <michael at snoyman.com> wrote:
> Hi Jeremy,
> I've CCed the web-devel list, as I think the discussion will be of interest
> to a number of readers there.
> When we were originally working on web-routes, you had mentioned the idea of
> including some form of support for query strings, and I said it was a bad
> idea. I'd like to backtrack on that statement: I *would* like to include
> support, and I'm including a patch that does just that. Let me explain the
> use case this is meant to serve, which will help explain my design
> decisions.
> Yesod includes a static file subsite. One trick a lot of sites are using
> these days is including a hash of the file contents in the query string of
> the URL and setting the expiration date of the file far in the future. This
> way, as long as the file contents stay the same, the browser should use the
> cached copy, and as soon as a new version is available, the HTML will
> reflect this by a change in the hash value.
> I wanted to provide this feature with Yesod, but realized there was no
> straight-forward way to do this. What I needed was to change the
> formatPathSegments function to have a type signature of: url -> ([String],
> [(String, String)]), where the second element in the tuple is the
> query-string parameters. This, however, presents a small problem: let's say
> that we want to add query string parameters *on top of* those provided by
> the formatPathSegments function; we could do manually addition textually,
> but we won't know whether to include is as "?foo=bar" or "&foo=bar"; the
> former should be used if formatPathSegments does not given any query string
> parameter, the latter if it does.
> I therefore modified the handleSite function to be: (url -> [(String,
> String)] -> String) -> url -> a. I also changed encodePathInfo to also
> encode the query string parameters, so its type is now: [String] ->
> [(String, String)] -> String. All the other changes were just to get the
> code to compile.
> I'm planning on this being a change throughout a few other libraries:
> web-routes-quasi will obviously change to reflect this, as will Yesod. One
> other perhaps unexpected change would be in Hamlet: the definition of Hamlet
> is now "type Hamlet = (url -> [(String, String)] -> String) -> Html ()". One
> nice side effect of this is query-string encoding code is now completely
> localized to web-routes, instead of copied throughout multiple packages.
> This at least implies to me that this is a good move.
> You'll notice that I have purposely *not* modified decodePathInfo and
> parsePathSegments; I still don't believe routing should be affected in any
> way by query string parameters.
> Look forward to hearing your thoughts on this,
> Michael