Implements CSV resnponse for the appropriate accept headers

src/PostgREST/App.hs

@@ -62,11 +62,12 @@ app conf reqBody req =
       then return $ responseLBS status416 [] "HTTP Range error"
       else do
         let qt = qualify table
+            from = fromMaybe 0 $ rangeOffset <$> range
             select = B.Stmt "select " V.empty True <>
                   parentheticT (
                     whereT qt qq $ countRows qt
                   ) <> commaq <> (
-                  asJsonWithCount
+                  bodyForAccept accept qt
                   . limitT range
                   . orderT (orderParse qq)
                   . whereT qt qq
@@ -75,7 +76,6 @@ app conf reqBody req =
         row <- H.maybeEx select
         let (tableTotal, queryTotal, body) =
               fromMaybe (0, 0, Just "" :: Maybe Text) row
-            from = fromMaybe 0 $ rangeOffset <$> range
             to = from+queryTotal-1
             contentRange = contentRangeH from to tableTotal
             status = rangeStatus from to tableTotal
@@ -233,6 +233,7 @@ app conf reqBody req =
     range         = rangeRequested hdrs
     allOrigins    = ("Access-Control-Allow-Origin", "*") :: Header
     lookupHeader  = flip lookup hdrs
+    accept        = lookupHeader hAccept
 
 sqlError :: t
 sqlError = undefined
@@ -246,6 +247,12 @@ rangeStatus from to total
   | (1 + to - from) < total = status206
   | otherwise               = status200
 
+bodyForAccept :: Maybe BS.ByteString -> QualifiedTable -> StatementT
+bodyForAccept accept table = 
+    case accept of
+      Just "text/csv" -> asCsvWithCount table
+      _ -> asJsonWithCount -- defaults to JSON
+
 contentRangeH :: Int -> Int -> Int -> Header
 contentRangeH from to total =
   ("Content-Range",

src/PostgREST/PgQuery.hs

@@ -100,10 +100,27 @@ countT s =
 countRows :: QualifiedTable -> PStmt
 countRows t = B.Stmt ("select pg_catalog.count(1) from " <> fromQt t) empty True
 
+asCsvWithCount :: QualifiedTable -> StatementT
+asCsvWithCount table = withCount . asCsv table
+
+asCsv :: QualifiedTable -> StatementT
+asCsv table s = s { B.stmtTemplate =
+    "(select string_agg(quote_ident(column_name::text), ',') from "
+    <> "(select column_name from information_schema.columns where quote_ident(table_schema) || '.' || table_name = '" 
+    <> fromQt table <> "' order by ordinal_position) h) || '\r' || "
+    <> "coalesce(string_agg(substring(t::text, 2, length(t::text) - 2), '\r'), '') from ("
+    <> B.stmtTemplate s <> ") t" }
+
 asJsonWithCount :: StatementT
-asJsonWithCount s = s { B.stmtTemplate =
+asJsonWithCount = withCount . asJson
-     "pg_catalog.count(t), array_to_json(array_agg(row_to_json(t)))::character varying from ("
+
-  <> B.stmtTemplate s <> ") t" }
+asJson :: StatementT
+asJson s = s { B.stmtTemplate =
+    "array_to_json(array_agg(row_to_json(t)))::character varying from ("
+    <> B.stmtTemplate s <> ") t" }
+
+withCount :: StatementT
+withCount s = s { B.stmtTemplate = "pg_catalog.count(t), " <> B.stmtTemplate s }
 
 asJsonRow :: StatementT
 asJsonRow s = s { B.stmtTemplate = "row_to_json(t) from (" <> B.stmtTemplate s <> ") t" }

test/Feature/QuerySpec.hs

@@ -3,6 +3,7 @@ module Feature.QuerySpec where
 import Test.Hspec
 import Test.Hspec.Wai
 import Test.Hspec.Wai.JSON
+import Network.HTTP.Types
 import Network.Wai.Test (SResponse(simpleHeaders))
 
 import SpecHelper
@@ -121,6 +122,12 @@ spec =
     it "without other constraints" $
       get "/items?order=asc.id" `shouldRespondWith` 200
 
+  describe "Accept headers" $
+    it "should respond with CSV to 'text/csv' request" $
+      request methodGet "/simple_pk"
+              (acceptHdrs "text/csv") ""
+        `shouldRespondWith` "k,extra\rxyyx,u\rxYYx,v"
+
   describe "Canonical location" $ do
     it "Sets Content-Location with alphabetized params" $
       get "/no_pk?b=eq.1&a=eq.1"

test/SpecHelper.hs

@@ -15,7 +15,7 @@ import qualified Data.Vector as V
 import Control.Monad (void)
 
 import Network.HTTP.Types.Header (Header, ByteRange, renderByteRange,
-                                  hRange, hAuthorization)
+                                  hRange, hAuthorization, hAccept)
 import Codec.Binary.Base64.String (encode)
 import Data.CaseInsensitive (CI(..))
 import Data.Maybe (fromMaybe)
@@ -84,6 +84,9 @@ loadFixture name =
 rangeHdrs :: ByteRange -> [Header]
 rangeHdrs r = [rangeUnit, (hRange, renderByteRange r)]
 
+acceptHdrs :: BS.ByteString -> [Header]
+acceptHdrs mime = [(hAccept, mime)]
+
 rangeUnit :: Header
 rangeUnit = ("Range-Unit" :: CI BS.ByteString, "items")