trace2: enable JSON source generation

Enable JSON source generation for Trace2 messages. This will further
help unlock AOT compilation options which cannot use reflection-based
APIs.

Replace the custom JSON naming policy with the built-in lower snake case
policy, and for good measure also explictly set the enum string values
as attributes on the members themselves.

Signed-off-by: Matthew John Cheetham <mjcheetham@outlook.com>

Author: mjcheetham

src/shared/Core/Trace2.cs

@@ -3,6 +3,7 @@
 using System.IO;
 using System.IO.Pipes;
 using System.Text;
+using System.Text.Json.Serialization;
 using System.Threading;
 
 namespace GitCredentialManager;
@@ -13,13 +14,21 @@ namespace GitCredentialManager;
 /// </summary>
 public enum Trace2Event
 {
+    [JsonStringEnumMemberName("version")]
     Version = 0,
+    [JsonStringEnumMemberName("start")]
     Start = 1,
+    [JsonStringEnumMemberName("exit")]
     Exit = 2,
+    [JsonStringEnumMemberName("child_start")]
     ChildStart = 3,
+    [JsonStringEnumMemberName("child_exit")]
     ChildExit = 4,
+    [JsonStringEnumMemberName("error")]
     Error = 5,
+    [JsonStringEnumMemberName("region_enter")]
     RegionEnter = 6,
+    [JsonStringEnumMemberName("region_leave")]
     RegionLeave = 7,
 }
 
@@ -28,9 +37,13 @@ public enum Trace2Event
 /// </summary>
 public enum Trace2ProcessClass
 {
+    [JsonStringEnumMemberName("none")]
     None = 0,
+    [JsonStringEnumMemberName("ui_helper")]
     UIHelper = 1,
+    [JsonStringEnumMemberName("git")]
     Git = 2,
+    [JsonStringEnumMemberName("other")]
     Other = 3
 }
 

src/shared/Core/Trace2Message.cs

@@ -15,6 +15,7 @@ namespace GitCredentialManager;
 [JsonSerializable(typeof(RegionEnterMessage))]
 [JsonSerializable(typeof(RegionLeaveMessage))]
 [JsonSourceGenerationOptions(
+    UseStringEnumConverter = true,
     PropertyNamingPolicy = JsonKnownNamingPolicy.SnakeCaseLower,
     PropertyNameCaseInsensitive = true
 )]
@@ -536,9 +537,3 @@ protected override string GetEventMessage(Trace2FormatTarget formatTarget)
         return Message;
     }
 }
-
-public class SnakeCaseNamingPolicy : JsonNamingPolicy
-{
-    public override string ConvertName(string name) =>
-        name.ToSnakeCase();
-}