Simplify code, fix loading non-existing file

src/TypedPersistence/Helper.fs

@@ -0,0 +1,17 @@
+namespace TypedPersistence
+
+open FSharp.Json
+
+module Helper =
+    type OptionBuilder() =
+        member x.Bind(v, f) = Option.bind f v
+        member x.Return v = Some v
+        member x.ReturnFrom o = o
+        member x.Zero() = None
+
+    let opt = OptionBuilder()
+
+    let deserializeJson<'a> content =
+        try
+            Json.deserialize<'a> content |> Some
+        with :? JsonDeserializationError -> None

src/TypedPersistence/Loading.fs

@@ -3,20 +3,23 @@ namespace TypedPersistence
 open FSharp.Json
 open System.IO
 
+open TypedPersistence.Helper
+
 [<AutoOpen>]
 module Loading =
+    let private getFileContent filepath =
+        if File.Exists filepath then File.ReadAllText filepath |> Some else None
+
     let getVersion (filepath: string) =
-        let content = File.ReadAllText filepath
-        try
-            Json.deserialize<OnlyVersion> content
-            |> (fun v -> v.version)
-            |> Some
-        with :? JsonDeserializationError -> None
+        opt {
+            let! content = getFileContent filepath
+            let! parsed = deserializeJson<OnlyVersion> content
+            return parsed.version
+        }
 
     let load<'a> (filepath: string) =
-        let content = File.ReadAllText filepath
-        try
-            Json.deserialize<VersionAndData<'a>> content
-            |> (fun d -> d.data)
-            |> Some
-        with :? JsonDeserializationError -> None
+        opt {
+            let! content = getFileContent filepath
+            let! parsed = deserializeJson<VersionAndData<'a>> content
+            return parsed.data
+        }

src/TypedPersistence/Saving.fs

@@ -6,7 +6,7 @@ open System.IO
 
 [<AutoOpen>]
 module Saving =
-    let saveVersion (filePath: string) (version: uint) (data: 'a) =
+    let saveVersion<'a> (filePath: string) (version: uint) (data: 'a) =
         // Alias for writing text with single arguments and not with tuple
         let writeAllText filePath content =
             // Create path, if not existing
@@ -22,4 +22,4 @@ module Saving =
         |> (fun text -> text + Environment.NewLine) // Somehow this final new line is missing
         |> writeAllText filePath
 
-    let save (filePath: string) (data: 'a) = saveVersion filePath 1u data
+    let save<'a> (filePath: string) (data: 'a) = saveVersion filePath 1u data

src/TypedPersistence/TypedPersistence.fsproj

@@ -6,6 +6,7 @@
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="Types.fs" />
+    <Compile Include="Helper.fs" />
     <Compile Include="Saving.fs" />
     <Compile Include="Loading.fs" />
   </ItemGroup>

tests/TypedPersistence.UnitTests/Tests.fs

@@ -33,7 +33,13 @@ let tests =
     testList
         "Test List"
         [ testList
-            "Save and load"
+            "Misc"
+              [ test "Load nonexisting file" {
+                    let value = load<string> "lalelu.txt"
+                    Expect.equal value None "Load on non-existing file should return None"
+                } ]
+          testList
+              "Save and load"
               [ basicSaveLoadTest<NonNull<string>> ()
                 basicSaveLoadTest<int> ()
                 basicSaveLoadTest<NonNull<string> list> ()