feat: Allow limit=0 in query params to return an empty array

src/PostgREST/RangeQuery.hs

@@ -10,6 +10,8 @@ module PostgREST.RangeQuery (
 , restrictRange
 , rangeGeq
 , allRange
+, limitZeroRange
+, hasLimitZero
 , NonnegRange
 , rangeStatusHeader
 , contentRangeH
@@ -74,6 +76,15 @@ rangeLeq :: Integer -> NonnegRange
 rangeLeq n =
   Range BoundaryBelowAll (BoundaryAbove n)
 
+-- Special case to allow limit 0 queries
+-- https://github.com/PostgREST/postgrest/issues/1121
+-- 0 <= x <= -1
+limitZeroRange :: Range Integer
+limitZeroRange = Range (BoundaryBelow 0) (BoundaryAbove (-1))
+
+hasLimitZero :: Range Integer -> Bool
+hasLimitZero r = rangeUpper r == rangeUpper limitZeroRange
+
 rangeStatusHeader :: NonnegRange -> Int64 -> Maybe Int64 -> (Status, Header)
 rangeStatusHeader topLevelRange queryTotal tableTotal =
   let lower = rangeOffset topLevelRange