Re: [web-devel] Last call for comments: WAI 0.4

On Wed, Mar 30, 2011 at 6:15 PM, Bas van Dijk wrote:

On 30 March 2011 18:01, Michael Snoyman wrote:

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On Wed, Mar 30, 2011 at 5:58 PM, Bas van Dijk wrote:

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On 28 March 2011 09:02, Michael Snoyman wrote:

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Just wanted to give everyone a last chance to give input on WAI 0.4 before its release.

Hi Michael,

What's the role of the errorHandler :: String -> IO () in the Request type: https://github.com/snoyberg/wai/blob/master/Network/Wai.hs#L73 ? It seems a bit odd to have this in a request.

Thanks,

Bas

The idea is to allow the server to give the application a general way of logging error messages. Frankly, I don't personally use it at all, and it was a relic from when I was trying to merge the original WAI (proposed by Johan) and Hack. Do people have ideas on how to make it more useful, or perhaps a better name for it? This is probably a good area for improvement.

Thanks for the explanation. I think it makes more sense to either remove the error handler or move it to the Application as in:

type Application = ErrorHandler -> Request -> Iteratee B.ByteString IO Response

type ErrorHandler = String -> IO ()

Bas

After some WAI-team internal discussions, we're going to go with the first option: removing errorHandler. We made this decision since: 1) None of us has actually ever used errorHandler in real life code. 2) None of the WAI backends do anything particularly intelligent with the data. I think they all just print to stderr. 3) As you've pointed out, it's illogical to have it as part of a Request. 4) Since the backends aren't really doing something intelligent, the programmer probably wants to supply his/her own logging function. This can happen internally to the Application, without talking to the handler at all. The only downside I can see is that Middlewares won't have automatic access to the logging function. However, I have yet to see a Middleware that uses it, so I don't think it's a big loss. I'll give another day or two for follow-up comments on WAI, and then release. Michael