Default to not over-escaping in SystemTextJson re #44

src/FsCodec.SystemTextJson/Options.fs

@@ -18,22 +18,27 @@ type Options private () =
             [<Optional; DefaultParameterValue(null)>] ?indent : bool,
             /// Render idiomatic camelCase for PascalCase items by using `PropertyNamingPolicy = CamelCase`. Defaults to false.
             [<Optional; DefaultParameterValue(null)>] ?camelCase : bool,
-            /// Ignore null values in input data; defaults to false.
-            [<Optional; DefaultParameterValue(null)>] ?ignoreNulls : bool) =
+            /// Ignore null values in input data, don't render fields with null values; defaults to `false`.
+            [<Optional; DefaultParameterValue(null)>] ?ignoreNulls : bool,
+            /// Drop escaping of HTML-sensitive characters. defaults to `false`.
+            [<Optional; DefaultParameterValue(null)>] ?unsafeRelaxedJsonEscaping : bool) =
 
         let indent = defaultArg indent false
         let camelCase = defaultArg camelCase false
         let ignoreNulls = defaultArg ignoreNulls false
+        let unsafeRelaxedJsonEscaping = defaultArg unsafeRelaxedJsonEscaping false
         let options = JsonSerializerOptions()
         if converters <> null then converters |> Array.iter options.Converters.Add
         if indent then options.WriteIndented <- true
         if camelCase then options.PropertyNamingPolicy <- JsonNamingPolicy.CamelCase; options.DictionaryKeyPolicy <- JsonNamingPolicy.CamelCase
         if ignoreNulls then options.IgnoreNullValues <- true
+        if unsafeRelaxedJsonEscaping then options.Encoder <- System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping
         options
 
-    /// Opinionated helper that creates serializer settings that provide good defaults for F#
-    /// - Always prepends `[JsonOptionConverter(); JsonRecordConverter()]` to any converters supplied
-    /// - no camel case conversion - assumption is you'll use records with camelCased names
+    /// Opinionated helper that creates serializer settings that represent good defaults for F# <br/>
+    /// - Always prepends `[JsonOptionConverter(); JsonRecordConverter()]` to any converters supplied <br/>
+    /// - no camel case conversion - assumption is you'll use records with camelCased names <br/>
+    /// - renders values with `UnsafeRelaxedJsonEscaping` - i.e. minimal escaping as per `NewtonsoftJson`<br/>
     /// Everything else is as per CreateDefault:- i.e. emit nulls instead of omitting fields, no indenting, no camelCase conversion
     static member Create
         (   /// List of converters to apply. Implicit [JsonOptionConverter(); JsonRecordConverter()] will be prepended and/or be used as a default
@@ -43,11 +48,14 @@ type Options private () =
             /// Render idiomatic camelCase for PascalCase items by using `PropertyNamingPolicy = CamelCase`.
             ///  Defaults to false on basis that you'll use record and tuple field names that are camelCase (but thus not `CLSCompliant`).
             [<Optional; DefaultParameterValue(null)>] ?camelCase : bool,
-            /// Ignore null values in input data; defaults to `false`.
-            [<Optional; DefaultParameterValue(null)>] ?ignoreNulls : bool) =
+            /// Ignore null values in input data, don't render fields with null values; defaults to `false`.
+            [<Optional; DefaultParameterValue(null)>] ?ignoreNulls : bool,
+            /// Drop escaping of HTML-sensitive characters. defaults to `true`.
+            [<Optional; DefaultParameterValue(null)>] ?unsafeRelaxedJsonEscaping : bool) =
 
         Options.CreateDefault(
             converters = (match converters with null | [||] -> defaultConverters | xs -> Array.append defaultConverters xs),
             ?ignoreNulls = ignoreNulls,
             ?indent = indent,
-            ?camelCase = camelCase)
+            ?camelCase = camelCase,
+            unsafeRelaxedJsonEscaping = defaultArg unsafeRelaxedJsonEscaping true)

tests/FsCodec.SystemTextJson.Tests/SerdesTests.fs

@@ -34,6 +34,28 @@ module StjCharacterization =
                 | Choice1Of2 v -> v = value
                 | Choice2Of2 m -> m.Contains "The JSON value could not be converted to Microsoft.FSharp.Core.FSharpOption`1[System.String]" @>
 
+    // System.Text.Json's JsonSerializerOptions by default escapes HTML-sensitive characters when generating JSON strings
+    // while this arguably makes sense as a default
+    // - it's not particularly relevant for event encodings
+    // - and is not in alignment with the FsCodec.NewtonsoftJson default options
+    // see https://github.com/dotnet/runtime/issues/28567#issuecomment-53581752 for lowdown
+    let asRequiredForExamples : System.Text.Json.Serialization.JsonConverter [] =
+        [| Converters.JsonOptionConverter()
+           Converters.JsonRecordConverter() |]
+    type OverescapedOptions() as this =
+        inherit TheoryData<System.Text.Json.JsonSerializerOptions>()
+
+        do // OOTB System.Text.Json over-escapes HTML-sensitive characters - `CreateDefault` honors this
+           this.Add(Options.CreateDefault(converters = asRequiredForExamples)) // the value we use here requires two custom Converters
+           // Options.Create provides a simple way to override it
+           this.Add(Options.Create(unsafeRelaxedJsonEscaping = false))
+    let [<Theory; ClassData(typedefof<OverescapedOptions>)>] ``provides various ways to use HTML-escaped encoding``(opts : System.Text.Json.JsonSerializerOptions) =
+        let value = { a = 1; b = Some "\"" }
+        let ser = Serdes.Serialize(value, opts)
+        test <@ ser = """{"a":1,"b":"\u0022"}""" @>
+        let des = Serdes.Deserialize(ser, opts)
+        test <@ value = des @>
+
 (* Serdes + default Options behavior, i.e. the stuff we do *)
 
 let [<Fact>] records () =
@@ -49,3 +71,10 @@ let [<Fact>] options () =
     test <@ ser = """{"a":1,"b":"str"}""" @>
     let des = Serdes.Deserialize ser
     test <@ value = des @>
+
+let [<Fact>] ``no over-escaping`` () =
+    let value = { a = 1; b = Some "\"+" }
+    let ser = Serdes.Serialize value
+    test <@ ser = """{"a":1,"b":"\"+"}""" @>
+    let des = Serdes.Deserialize ser
+    test <@ value = des @>