Improve exception error messages for getAddrInfo and getNameInfo

[MaxGabriel]

@develop7 ran into an issue with yesod devel (yesodweb/yesod#1471) and got the following error message:

devel.hs: Network.Socket.getAddrInfo: does not exist (Name or service not known)

It would be useful to have a more detailed error message to aid in debugging this exception. The new message looks like this:

> getAddrInfo Nothing (Just "127.0.0.1") (Just "foo")
*** Exception: Network.Socket.getAddrInfo (called with preferred socket type/protocol: Nothing, host name: Just "127.0.0.1", service name: Just "foo"): does not exist (nodename nor servname provided, or not known)

I think a more verbose error message is well worth it, especially since these kind of lower-level, underlying issues can be hard to debug.

(I added a similar error message for getNameInfo since it was right there)

[eborden]

These look great! Thanks.

[MaxGabriel]

Thanks @eborden! Didn’t realize you did stackage and network, thanks for all your work :)

[MaxGabriel]

Oh wait I'm confusing you with bergmark, sorry :P

[develop7]

There's an issue with this PR: the defaultHints initializes the addrAddress and addrCanonName of AddrInfo with undefined which explodes like this:

Devel application launched: http://localhost:3000
devel.hs: Prelude.undefined
CallStack (from HasCallStack):
  error, called at libraries/base/GHC/Err.hs:79:14 in base:GHC.Err
  undefined, called at Network/Socket.hsc:1407:40 in network-2.6.3.2-Elf6Dxkfz0iKjb1zv5eBTP:Network.Socket

[MaxGabriel]

Oh hm, I assumed that correct usage of the library was to set the undefined fields to something sensible first

[MaxGabriel]

I see that the docs for defaultHints say:

-- | Default hints for address lookup with 'getAddrInfo'.  The values
-- of the 'addrAddress' and 'addrCanonName' fields are 'undefined',
-- and are never inspected by 'getAddrInfo'.
--

So it sounds like expected usage is for those fields to be undefined. I can think of a couple workarounds:

1. Print only the fields that are not undefined by default
2. Don’t print the AddrInfo field

I’d probably implement (1) unless you have further advice on this @eborden

[eborden]

(1) Seems like a reasonable approach. Do you plan to open a PR?

[MaxGabriel]

Yeah, but I’m going skiing for a few days so might be a bit