Polish tests

tests/FsCodec.SystemTextJson.Tests/SerdesTests.fs

@@ -80,7 +80,7 @@ let [<Fact>] ``RejectNullStringConverter rejects null strings`` () =
     let value = { c = 1; d = null }
     raises<ArgumentNullException> <@ serdes.Serialize value @>
 
-type WithList = { x: int; y: list<int> }
+type WithList = { x: int; y: list<int>; z: Set<int> }
 
 let [<Fact>] ``RejectNullConverter rejects null lists and Sets`` () =
 #if false // requires WithList to be CLIMutable, which would be a big imposition
@@ -93,18 +93,28 @@ let [<Fact>] ``RejectNullConverter rejects null lists and Sets`` () =
                     if pt.IsGenericType && (let gtd = pt.GetGenericTypeDefinition() in gtd = typedefof<list<_>> || gtd = typedefof<Set<_>>) then
                         p.IsRequired <- true)
     let serdes = Options.Create(TypeInfoResolver = tir) |> Serdes
+    raises<exn> <@ serdes.Deserialize<WithList> """{"x":0}""" @>
 #else
     let serdes = Options.Create(rejectNull = true) |> Serdes
-#endif
 
     // Fails with NRE when RejectNullConverter delegates to Default list<int> Converter
     // seems akin to https://github.com/dotnet/runtime/issues/86483
-    let res = serdes.Deserialize<WithList> """{"x":0,"y":[1]}"""
-    test <@ [1] = res.y @>
+    // let res = serdes.Deserialize<WithList> """{"x":0,"y":[1]}"""
+    // test <@ [1] = res.y @>
 
+    // PROBLEM: Doesn't raise
     raises<exn> <@ serdes.Deserialize<WithList> """{"x":0}""" @>
-    // PROBLEM: there doesn't seem to be a way to intercept explicitly passed nulls
+    // PROBLEM: doesnt raise - there doesn't seem to be a way to intercept explicitly passed nulls
     // raises<JsonException> <@ serdes.Deserialize<WithList> """{"x":0,"y":null}""" @>
+#endif
+
+#if false // I guess TypeShape is doing a reasaonable thing not propagating
+    // PROBLEM: TypeShape.Generic.exists does not call the predicate if the list or set is `null`
+    let res = serdes.Deserialize<WithList> """{"x":0}"""
+    let hasNullList = TypeShape.Generic.exists (fun (x: int list) -> obj.ReferenceEquals(x, null))
+    let hasNullSet = TypeShape.Generic.exists (fun (x: Set<int>) -> obj.ReferenceEquals(x, null))
+    test <@ hasNullList res && hasNullSet res @>
+#endif
 
 let [<Fact>] ``RejectNullStringConverter serializes strings correctly`` () =
     let serdes = Serdes(Options.Create(rejectNullStrings = true))