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Unbreak lateral joins by introducing a completely different ValidOnClause constraint

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This commit is contained in:
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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16
src/Database/Esqueleto/Experimental/From/Join.hs
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@ -23,9 +23,14 @@ 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)
(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
@ -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`