Reintroduce withConnection without pooling

Rename the pooling version to `withClient`.

Author: anttih

MODULE.md

@@ -112,6 +112,15 @@ withConnection :: forall eff a. ConnectionInfo -> (Client -> Aff (db :: DB | eff
 Connects to the database, calls the provided function with the client
 and returns the results.
 
+#### `withClient`
+
+``` purescript
+withClient :: forall eff a. ConnectionInfo -> (Client -> Aff (db :: DB | eff) a) -> Aff (db :: DB | eff) a
+```
+
+Takes a Client from the connection pool, runs the given function with
+the client and returns the results.
+
 #### `end`
 
 ``` purescript

src/Database/Postgres.purs

@@ -13,6 +13,7 @@ module Database.Postgres
   , queryValue, queryValue_
   , queryOne, queryOne_
   , withConnection
+  , withClient
   ) where
 
 import Control.Alt
@@ -117,11 +118,28 @@ withConnection :: forall eff a
   . ConnectionInfo
   -> (Client -> Aff (db :: DB | eff) a)
   -> Aff (db :: DB | eff) a
-withConnection info p = runFn2 _withConnection (mkConnectionString info) p
+withConnection info p = do
+  client <- connect info
+  finally (p client) $ liftEff (end client)
+
+-- | Takes a Client from the connection pool, runs the given function with
+-- | the client and returns the results.
+withClient :: forall eff a
+  . ConnectionInfo
+  -> (Client -> Aff (db :: DB | eff) a)
+  -> Aff (db :: DB | eff) a
+withClient info p = runFn2 _withClient (mkConnectionString info) p
 
 liftError :: forall e a. ForeignError -> Aff e a
 liftError err = throwError $ error (show err)
 
+finally :: forall eff a. Aff eff a -> Aff eff Unit -> Aff eff a
+finally a sequel = do
+  res <- attempt a
+  sequel
+  either throwError pure res
+
+
 foreign import connect' """
   function connect$prime(conString) {
     return function(success, error) {
@@ -139,9 +157,9 @@ foreign import connect' """
   }
   """ :: forall eff. String -> Aff (db :: DB | eff) Client
 
-foreign import _withConnection
+foreign import _withClient
   """
-  function _withConnection(conString, cb) {
+  function _withClient(conString, cb) {
     return function(success, error) {
       var pg = require('pg');
       pg.connect(conString, function(err, client, done) {

test/Main.purs

@@ -65,7 +65,7 @@ exampleError = withConnection connectionInfo $ \c -> do
   queryOne_ (Query "select year from artist") c
 
 exampleQueries :: forall eff. Aff (trace :: Trace, db :: DB | eff) Unit
-exampleQueries = withConnection connectionInfo $ \c -> do
+exampleQueries = withClient connectionInfo $ \c -> do
   liftEff $ trace "Example queries with params:"
   execute_ (Query "delete from artist") c
   execute_ (Query "insert into artist values ('Led Zeppelin', 1968)") c