[#22] Support DictionaryKeyPolicy for Map<string, 'T>

src/FSharp.SystemTextJson/Collection.fs

@@ -1,4 +1,4 @@
-namespace System.Text.Json.Serialization
+namespace System.Text.Json.Serialization
 
 open System
 open System.Text.Json
@@ -93,7 +93,11 @@ type JsonStringMapConverter<'V>() =
     override _.Write(writer, value, options) =
         writer.WriteStartObject()
         for kv in value do
-            writer.WritePropertyName(kv.Key)
+            let k =
+                match options.DictionaryKeyPolicy with
+                | null -> kv.Key
+                | p -> p.ConvertName kv.Key
+            writer.WritePropertyName(k)
             JsonSerializer.Serialize<'V>(writer, kv.Value, options)
         writer.WriteEndObject()
 

tests/FSharp.SystemTextJson.Tests/Test.Collection.fs

@@ -1,5 +1,6 @@
-module Tests.Collection
+module Tests.Collection
 
+open System.Collections.Generic
 open System.Text.Json.Serialization
 open System.Text.Json
 open Xunit
@@ -50,6 +51,24 @@ let ``serialize string-keyed map`` (m: Map<NonNull<string>, int>) =
     let actual = JsonSerializer.Serialize(m, options)
     Assert.Equal(expected, actual)
 
+let keyPolicyOptions = JsonSerializerOptions(DictionaryKeyPolicy = JsonNamingPolicy.CamelCase)
+keyPolicyOptions.Converters.Add(JsonFSharpConverter())
+
+[<Property>]
+let ``deserialize string-keyed map with key policy`` (m: Map<NonNull<string>, int>) =
+    let m = (Map.empty, m) ||> Map.fold (fun m (NonNull k) v -> Map.add k v m)
+    let ser = "{" + String.concat "," (Seq.map serKV1 m) + "}"
+    let actual = JsonSerializer.Deserialize<Map<string, int>>(ser, keyPolicyOptions)
+    Assert.Equal<Map<string, int>>(m, actual)
+
+[<Property>]
+let ``serialize string-keyed map with key policy`` (m: Map<NonNull<string>, int>) =
+    let m = (Map.empty, m) ||> Map.fold (fun m (NonNull k) v -> Map.add k v m)
+    let ccm = m |> Seq.map (fun (KeyValue(k, v)) -> KeyValuePair(JsonNamingPolicy.CamelCase.ConvertName k, v))
+    let expected = "{" + String.concat "," (Seq.map serKV1 ccm) + "}"
+    let actual = JsonSerializer.Serialize(m, keyPolicyOptions)
+    Assert.Equal(expected, actual)
+
 let serKV2 (KeyValue (k: int, v: string)) =
     "[" + JsonSerializer.Serialize(k) + "," + JsonSerializer.Serialize(v) + "]"