add support for List/Array.IsEmpty and Option.IsSome/None

Author: eiriktsarpalis

src/FSharp.DynamoDB/Expression/ConditionalExpr.fs

@@ -305,6 +305,18 @@ let extractQueryExpr (recordInfo : RecordInfo) (expr : Expr) : ConditionalExpres
             | SpecificCall2 <@ NOT_EXISTS @> (None, _, _, [AttributeGet attr]) ->
                 Attribute_Not_Exists attr.Id
 
+            | SpecificCall2 <@ Array.isEmpty @> (None, _, _, [AttributeGet attr]) -> 
+                Attribute_Not_Exists attr.Id
+
+            | SpecificCall2 <@ List.isEmpty @> (None, _, _, [AttributeGet attr]) -> 
+                Attribute_Not_Exists attr.Id
+
+            | SpecificCall2 <@ Option.isSome @> (None, _, _, [AttributeGet attr]) -> 
+                Attribute_Exists attr.Id
+
+            | SpecificCall2 <@ Option.isNone @> (None, _, _, [AttributeGet attr]) -> 
+                Attribute_Not_Exists attr.Id
+
             | _ -> invalidQuery()
 
         let queryExpr = extractQuery body

tests/FSharp.DynamoDB.Tests/ConditionalExpressionTests.fs

@@ -308,6 +308,16 @@ type ``Conditional Expression Tests`` () =
         table.PutItem(item, <@ fun r -> r.List.Length >= list.Length @>) |> ignore
         table.PutItem(item, <@ fun r -> List.length r.List >= list.Length @>) |> ignore
 
+    [<Fact>]
+    let ``List-isEmpty precondition`` () =
+        let item = { mkItem() with List = [] }
+        let key = table.PutItem item
+        table.PutItem({item with List = [42L]}, <@ fun r -> List.isEmpty r.List @>) |> ignore
+        
+        fun () -> table.PutItem(item, <@ fun r -> List.isEmpty r.List  @>)
+        |> shouldFailwith<_, ConditionalCheckFailedException>
+
+
     [<Fact>]
     let ``Set-count precondition`` () =
         let item = mkItem()