Add Read instances for SockAddr/SockEndpoint, make Show instances follow contract

The old Show behaviour is moved into the 'showSockAddr' function, with a new
function 'readSockAddr' that acts as its opposite.

Author: infinity0

Network/Socket.hs

@@ -190,6 +190,8 @@ module Network.Socket
     , resolveEndpoint
     -- * Basic socket address type
     , SockAddr(..)
+    , readSockAddr
+    , showSockAddr
     , sockAddrFamily
     , isSupportedSockAddr
     , getPeerName

Network/Socket/Info.hsc

@@ -242,7 +242,9 @@ defaultHints = AddrInfo {
 --
 -- >>> addr:_ <- getAddrInfo (Just hints) (Just "127.0.0.1") (Just "http")
 -- >>> addrAddress addr
--- 127.0.0.1:80
+-- SockAddrInet 80 16777343
+-- >>> showSockAddr (addrAddress addr)
+-- "127.0.0.1:80"
 
 getAddrInfo
     :: Maybe AddrInfo -- ^ preferred socket type or protocol
@@ -415,22 +417,29 @@ unpackBits ((k,v):xs) r
 -----------------------------------------------------------------------------
 -- SockAddr
 
-instance Show SockAddr where
+-- | Read a string representing a socket address.
+readSockAddr :: PortNumber -> String -> Either String SockAddr
+readSockAddr defPort hostport = readSockEndpoint defPort hostport >>= \r -> case r of
+  EndpointByName h _ -> Left $ "expected address but got hostname: " <> h
+  EndpointByAddr a -> Right a
+
+showSockAddr :: SockAddr -> String
 #if defined(DOMAIN_SOCKET_SUPPORT)
-  showsPrec _ (SockAddrUnix str) = showString str
+showSockAddr (SockAddrUnix str) = showString str ""
 #else
-  showsPrec _ SockAddrUnix{} = error "showsPrec: not supported"
+showSockAddr SockAddrUnix{} = error "showsPrec: not supported"
 #endif
-  showsPrec _ (SockAddrInet port ha)
+showSockAddr (SockAddrInet port ha)
    = showHostAddress ha
    . showString ":"
    . shows port
-  showsPrec _ (SockAddrInet6 port _ ha6 _)
+   $ ""
+showSockAddr (SockAddrInet6 port _ ha6 _)
    = showChar '['
    . showHostAddress6 ha6
    . showString "]:"
    . shows port
-
+   $ ""
 
 -- Taken from on the implementation of showIPv4 in Data.IP.Addr
 showHostAddress :: HostAddress -> ShowS
@@ -512,7 +521,7 @@ readSockEndpoint defPort hostport = case hostport of
 showSockEndpoint :: SockEndpoint -> String
 showSockEndpoint n = case n of
   EndpointByName h p -> h <> ":" <> show p
-  EndpointByAddr a -> show a
+  EndpointByAddr a -> showSockAddr a
 
 -- | Resolve a socket endpoint into a list of socket addresses.
 -- The result is always non-empty; Haskell throws an exception if name

Network/Socket/Syscall.hs

@@ -68,7 +68,7 @@ import Network.Socket.Types
 -- >>> sock <- socket (addrFamily addr) (addrSocketType addr) (addrProtocol addr)
 -- >>> Network.Socket.bind sock (addrAddress addr)
 -- >>> getSocketName sock
--- 127.0.0.1:5000
+-- SockAddrInet 5000 16777343
 socket :: Family         -- Family Name (usually AF_INET)
        -> SocketType     -- Socket Type (usually Stream)
        -> ProtocolNumber -- Protocol Number (getProtocolByName to find value)

Network/Socket/Types.hsc

@@ -1058,7 +1058,7 @@ type ScopeID = Word32
 data SockEndpoint
   = EndpointByName !String !PortNumber
   | EndpointByAddr !SockAddr
-  deriving (Eq, Ord)
+  deriving (Eq, Ord, Read, Show)
 
 -- | Socket addresses.
 --  The existence of a constructor does not necessarily imply that
@@ -1076,7 +1076,7 @@ data SockAddr
   -- | The path must have fewer than 104 characters. All of these characters must have code points less than 256.
   | SockAddrUnix
         String           -- sun_path
-  deriving (Eq, Ord)
+  deriving (Eq, Ord, Read, Show)
 
 instance NFData SockAddr where
   rnf (SockAddrInet _ _) = ()

tests/Network/SocketSpec.hs

@@ -320,20 +320,20 @@ spec = do
     describe "show SocketAddr" $ do
         it "works for IPv4 address" $
             let addr = SockAddrInet 80 (tupleToHostAddress (127, 0, 0, 1)) in
-            show addr `shouldBe` "127.0.0.1:80"
+            showSockAddr addr `shouldBe` "127.0.0.1:80"
 
         it "works for IPv6 address" $
             let addr = SockAddrInet6 80 0
                            (tupleToHostAddress6 (0x2001, 0x0db8, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7)) 0 in
-            show addr `shouldBe` "[2001:db8:2:3:4:5:6:7]:80"
+            showSockAddr addr `shouldBe` "[2001:db8:2:3:4:5:6:7]:80"
 
         it "works for IPv6 address with zeros" $
             let addr = SockAddrInet6 80 0
                            (tupleToHostAddress6 (0x2001, 0x0db8, 0x2, 0x3, 0x0, 0x0, 0x0, 0x7)) 0 in
-            show addr `shouldBe` "[2001:db8:2:3::7]:80"
+            showSockAddr addr `shouldBe` "[2001:db8:2:3::7]:80"
 
         it "works for multicast IPv6 address with reserved scope" $ do
             let addr = SockAddrInet6 80 0
                            (tupleToHostAddress6 (0xff01, 0x1234, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7)) 0
-            show addr `shouldBe` "[ff01:1234:2:3:4:5:6:7]:80"
+            showSockAddr addr `shouldBe` "[ff01:1234:2:3:4:5:6:7]:80"