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Unbreak lateral joins by introducing a completely different ValidOnClause constraint

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belevy 2021-02-13 19:50:02 -06:00
parent 9bf34761a4
commit 096c1acfd6
1 changed files with 33 additions and 25 deletions
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58
src/Database/Esqueleto/Experimental/From/Join.hs
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@ -1,32 +1,37 @@
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UndecidableInstances #-}
module Database.Esqueleto.Experimental.From.Join
where
import Data.Bifunctor (first)
import Data.Kind (Constraint)
import Data.Proxy
import qualified Data.Text.Lazy.Builder as TLB
import Database.Esqueleto.Experimental.From
import Database.Esqueleto.Experimental.From.SqlSetOperation
import Database.Esqueleto.Experimental.ToAlias
import Database.Esqueleto.Experimental.ToAliasReference
import Database.Esqueleto.Experimental.ToMaybe
import Database.Esqueleto.Internal.Internal hiding
(From(..), from, fromJoin, on)
import Database.Esqueleto.Internal.PersistentImport
(Entity(..), EntityField, PersistEntity, PersistField)
import GHC.TypeLits
import Data.Bifunctor (first)
import Data.Kind (Constraint)
import Data.Proxy
import qualified Data.Text.Lazy.Builder as TLB
import Database.Esqueleto.Experimental.From
import Database.Esqueleto.Experimental.From.SqlSetOperation
import Database.Esqueleto.Experimental.ToAlias
import Database.Esqueleto.Experimental.ToAliasReference
import Database.Esqueleto.Experimental.ToMaybe
import Database.Esqueleto.Internal.Internal hiding
(From (..),
from,
fromJoin,
on)
import Database.Esqueleto.Internal.PersistentImport (Entity (..),
EntityField,
PersistEntity,
PersistField)
import GHC.TypeLits
-- | A left-precedence pair. Pronounced \"and\". Used to represent expressions
-- that have been joined together.
@ -46,6 +51,9 @@ instance (ToMaybe a, ToMaybe b) => ToMaybe (a :& b) where
type ToMaybeT (a :& b) = (ToMaybeT a :& ToMaybeT b)
toMaybe (a :& b) = (toMaybe a :& toMaybe b)
class ValidOnClause a
instance {-# OVERLAPPABLE #-} ToFrom a a' => ValidOnClause a
instance ValidOnClause (a -> SqlQuery b)
-- | An @ON@ clause that describes how two tables are related. This should be
-- used as an infix operator after a 'JOIN'. For example,
@ -57,7 +65,7 @@ instance (ToMaybe a, ToMaybe b) => ToMaybe (a :& b) where
-- \`on\` (\\(p :& bP) ->
-- p ^. PersonId ==. bP ^. BlogPostAuthorId)
-- @
on :: ToFrom a a' => a -> (b -> SqlExpr (Value Bool)) -> (a, b -> SqlExpr (Value Bool))
on :: ValidOnClause a => a -> (b -> SqlExpr (Value Bool)) -> (a, b -> SqlExpr (Value Bool))
on = (,)
infix 9 `on`