From 2a3681e6b65f004d87d22cd53f1966bbe9437125 Mon Sep 17 00:00:00 2001
From: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
Date: Thu, 3 Mar 2016 14:13:36 +0200
Subject: [PATCH] add support for List/Array.IsEmpty and Option.IsSome/None

---
 src/FSharp.DynamoDB/Expression/ConditionalExpr.fs    | 12 ++++++++++++
 .../ConditionalExpressionTests.fs                    | 10 ++++++++++
 2 files changed, 22 insertions(+)

diff --git a/src/FSharp.DynamoDB/Expression/ConditionalExpr.fs b/src/FSharp.DynamoDB/Expression/ConditionalExpr.fs
index 45f7b53..ab5f1fa 100644
--- a/src/FSharp.DynamoDB/Expression/ConditionalExpr.fs
+++ b/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
diff --git a/tests/FSharp.DynamoDB.Tests/ConditionalExpressionTests.fs b/tests/FSharp.DynamoDB.Tests/ConditionalExpressionTests.fs
index 0616b83..70fc7db 100644
--- a/tests/FSharp.DynamoDB.Tests/ConditionalExpressionTests.fs
+++ b/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()