fix: Error when requesting count with Null embed filters

src/PostgREST/Query/QueryBuilder.hs

@@ -203,7 +203,7 @@ readPlanToCountQuery (Node ReadPlan{from=mainQi, fromAlias=tblAlias, where_=logi
     then mempty
     else " WHERE " ) <>
   intercalateSnippet " AND " (
-    map (pgFmtLogicTree qi) logicForest ++
+    map (pgFmtLogicTreeCount qi) logicForest ++
     map pgFmtJoinCondition relJoinConds ++
     subQueries
   )
@@ -216,6 +216,18 @@ readPlanToCountQuery (Node ReadPlan{from=mainQi, fromAlias=tblAlias, where_=logi
       if joinType == Just JTInner
         then ("EXISTS (" <> readPlanToCountQuery readReq <> " )"):rest
         else rest
+    findNullEmbedRel fld = find (\(Node ReadPlan{relAggAlias} _) -> fld == relAggAlias) forest
+
+    -- https://github.com/PostgREST/postgrest/pull/2930#discussion_r1325293698
+    pgFmtLogicTreeCount :: QualifiedIdentifier -> CoercibleLogicTree -> SQL.Snippet
+    pgFmtLogicTreeCount qiCount (CoercibleExpr hasNot op frst) = SQL.sql notOp <> " (" <> intercalateSnippet (opSql op) (pgFmtLogicTreeCount qiCount <$> frst) <> ")"
+      where
+        notOp =  if hasNot then "NOT" else mempty
+        opSql And = " AND "
+        opSql Or  = " OR "
+    pgFmtLogicTreeCount _ (CoercibleStmnt (CoercibleFilterNullEmbed hasNot fld)) =
+      maybe mempty (\x -> (if not hasNot then "NOT " else mempty) <> "EXISTS (" <> readPlanToCountQuery x <> ")") (findNullEmbedRel fld)
+    pgFmtLogicTreeCount qiCount (CoercibleStmnt flt) = pgFmtFilter qiCount flt
 
 limitedQuery :: SQL.Snippet -> Maybe Integer -> SQL.Snippet
 limitedQuery query maxRows = query <> SQL.sql (maybe mempty (\x -> " LIMIT " <> BS.pack (show x)) maxRows)

src/PostgREST/Query/SqlFragment.hs

@@ -15,6 +15,7 @@ module PostgREST.Query.SqlFragment
   , mutRangeF
   , orderF
   , pgFmtColumn
+  , pgFmtFilter
   , pgFmtIdent
   , pgFmtJoinCondition
   , pgFmtLogicTree

test/spec/Feature/Query/RelatedQueriesSpec.hs

@@ -2,6 +2,7 @@ module Feature.Query.RelatedQueriesSpec where
 
 import Network.Wai (Application)
 
+import Network.HTTP.Types
 import Test.Hspec
 import Test.Hspec.Wai
 import Test.Hspec.Wai.JSON
@@ -275,3 +276,105 @@ spec = describe "related queries" $ do
         { matchStatus  = 200
         , matchHeaders = [matchContentTypeJson]
         }
+
+    it "works with count=exact" $ do
+      request methodGet "/projects?select=name,clients(name)&clients=not.is.null"
+        [("Prefer", "count=exact")] ""
+       `shouldRespondWith`
+        [json|[
+          {"name":"Windows 7", "clients":{"name":"Microsoft"}},
+          {"name":"Windows 10", "clients":{"name":"Microsoft"}},
+          {"name":"IOS", "clients":{"name":"Apple"}},
+          {"name":"OSX", "clients":{"name":"Apple"}}
+        ]|]
+        { matchStatus  = 200
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Range" <:> "0-3/4" ]
+        }
+      request methodGet "/projects?select=name,clients()&clients=is.null"
+        [("Prefer", "count=exact")] ""
+       `shouldRespondWith`
+        [json|[{"name":"Orphan"}]|]
+        { matchStatus  = 200
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Range" <:> "0-0/1" ]
+        }
+      request methodGet "/client?select=*,clientinfo(),contact()&clientinfo.other=ilike.*main*&contact.name=ilike.*tabby*&or=(clientinfo.not.is.null,contact.not.is.null)"
+        [("Prefer", "count=exact")] ""
+       `shouldRespondWith`
+        [json|[
+          {"id":1,"name":"Walmart"},
+          {"id":2,"name":"Target"}
+        ]|]
+        { matchStatus  = 200
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Range" <:> "0-1/2" ]
+        }
+
+    it "works with count=planned" $ do
+      request methodGet "/projects?select=name,clients(name)&clients=not.is.null"
+        [("Prefer", "count=planned")] ""
+       `shouldRespondWith`
+        [json|[
+          {"name":"Windows 7", "clients":{"name":"Microsoft"}},
+          {"name":"Windows 10", "clients":{"name":"Microsoft"}},
+          {"name":"IOS", "clients":{"name":"Apple"}},
+          {"name":"OSX", "clients":{"name":"Apple"}}
+        ]|]
+        { matchStatus  = 206
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Range" <:> "0-3/1200" ]
+        }
+      request methodGet "/projects?select=name,clients()&clients=is.null"
+        [("Prefer", "count=planned")] ""
+       `shouldRespondWith`
+        [json|[{"name":"Orphan"}]|]
+        { matchStatus  = 200
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Range" <:> "0-0/1" ]
+        }
+      request methodGet "/client?select=*,clientinfo(),contact()&clientinfo.other=ilike.*main*&contact.name=ilike.*tabby*&or=(clientinfo.not.is.null,contact.not.is.null)"
+        [("Prefer", "count=planned")] ""
+       `shouldRespondWith`
+        [json|[
+          {"id":1,"name":"Walmart"},
+          {"id":2,"name":"Target"}
+        ]|]
+        { matchStatus  = 206
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Range" <:> "0-1/952" ]
+        }
+
+    it "works with count=estimated" $ do
+      request methodGet "/projects?select=name,clients(name)&clients=not.is.null"
+        [("Prefer", "count=estimated")] ""
+       `shouldRespondWith`
+        [json|[
+          {"name":"Windows 7", "clients":{"name":"Microsoft"}},
+          {"name":"Windows 10", "clients":{"name":"Microsoft"}},
+          {"name":"IOS", "clients":{"name":"Apple"}},
+          {"name":"OSX", "clients":{"name":"Apple"}}
+        ]|]
+        { matchStatus  = 206
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Range" <:> "0-3/1200" ]
+        }
+      request methodGet "/projects?select=name,clients()&clients=is.null"
+        [("Prefer", "count=estimated")] ""
+       `shouldRespondWith`
+        [json|[{"name":"Orphan"}]|]
+        { matchStatus  = 200
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Range" <:> "0-0/1" ]
+        }
+      request methodGet "/client?select=*,clientinfo(),contact()&clientinfo.other=ilike.*main*&contact.name=ilike.*tabby*&or=(clientinfo.not.is.null,contact.not.is.null)"
+        [("Prefer", "count=estimated")] ""
+       `shouldRespondWith`
+        [json|[
+          {"id":1,"name":"Walmart"},
+          {"id":2,"name":"Target"}
+        ]|]
+        { matchStatus  = 206
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Range" <:> "0-1/952" ]
+        }