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postgresql-simple-interval.cabal

@@ -27,6 +27,7 @@ common library
     attoparsec ^>=0.14.4,
     base >=4.13 && <4.22,
     bytestring >=0.10.10 && <0.13,
+    postgresql-simple ^>=0.7,
 
   default-language: Haskell2010
   ghc-options:
@@ -61,7 +62,6 @@ library
   import: library
   build-depends:
     persistent ^>=2.17,
-    postgresql-simple ^>=0.7,
     scientific ^>=0.3.8,
     text >=1.2.4 && <1.3 || >=2.0 && <2.2,
 

source/library/Database/PostgreSQL/Simple/Interval/Unstable.hs

@@ -35,6 +35,12 @@ import qualified Database.PostgreSQL.Simple.TypeInfo.Static as Postgres
 -- - 'Data.Time.CalendarDiffTime': Does not handle days. Embeds a
 --   @NominalDiffTime@. Is not bounded.
 -- - 'Data.Time.CalendarDiffDays': Does not handle seconds. Is not bounded.
+--
+-- WARNING: The PostgreSQL interval parser is broken in versions prior to 15.
+-- It is not possible to round trip all intervals through PostgreSQL on those
+-- versions. You should upgrade to at least PostgreSQL version 15. For more
+-- information, see this patch:
+-- <https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=e39f99046>
 data Interval = MkInterval
   { months :: !Int.Int32,
     days :: !Int.Int32,

source/test-suite/Main.hs

@@ -7,7 +7,9 @@ import qualified Data.ByteString as ByteString
 import qualified Data.ByteString.Builder as Builder
 import qualified Data.ByteString.Lazy as LazyByteString
 import qualified Data.Int as Int
+import qualified Database.PostgreSQL.Simple as Postgres
 import qualified Database.PostgreSQL.Simple.Interval.Unstable as I
+import qualified Database.PostgreSQL.Simple.ToField as Postgres
 import qualified Test.Hspec as H
 
 main :: IO ()
@@ -143,13 +145,32 @@ spec = H.describe "Database.PostgreSQL.Simple.Interval" $ do
         let actual = Attoparsec.parseOnly I.parse input
         actual `H.shouldBe` Right interval
 
+  H.describe "integration" $ do
+    Monad.forM_ intervalStyles $ \(style, field) -> do
+      H.describe ("with style " <> show style) $ do
+        Monad.forM_ examples $ \example -> do
+          H.it ("round trips " <> show (field example)) $ do
+            let interval = exampleInterval example
+            actual <- Postgres.withConnect Postgres.defaultConnectInfo $ \connection -> do
+              Postgres.withTransaction connection $ do
+                Monad.void $ Postgres.execute connection "set local intervalstyle = ?" [style]
+                Postgres.query connection "select ?" [interval]
+            actual `H.shouldBe` [Postgres.Only interval]
+
 data IntervalStyle
   = Iso8601
   | Postgres
   | PostgresVerbose
   | SqlStandard
   deriving (Eq, Show)
 
+instance Postgres.ToField IntervalStyle where
+  toField style = Postgres.Plain $ case style of
+    Iso8601 -> "iso_8601"
+    Postgres -> "postgres"
+    PostgresVerbose -> "postgres_verbose"
+    SqlStandard -> "sql_standard"
+
 data Example = MkExample
   { exampleInterval :: I.Interval,
     exampleIso8601 :: ByteString.ByteString,