Optimize HTMX configuration serialization

src/Ramstack.HtmxToolkit/HtmxBinaryTypeJsonConverter.cs

@@ -17,13 +17,8 @@ internal sealed class HtmxBinaryTypeJsonConverter : JsonConverter<HtmxBinaryType
     /// <inheritdoc />
     public override void Write(Utf8JsonWriter writer, HtmxBinaryType? value, JsonSerializerOptions options)
     {
-        if (value is null)
-        {
-            writer.WriteNullValue();
-        }
-        else
-        {
-            writer.WriteStringValue(value.GetValueOrDefault().GetWsBinaryTypeValue());
-        }
+        // NOTE: value is never null here: null-valued properties are omitted
+        // by JsonIgnoreCondition.WhenWritingNull before this converter is invoked.
+        writer.WriteStringValue(value.GetValueOrDefault().GetWsBinaryTypeValue());
     }
 }

src/Ramstack.HtmxToolkit/HtmxConfig.cs

@@ -1,12 +1,16 @@
 using System.Text.Json.Serialization;
 
+using Microsoft.AspNetCore.Html;
+
 namespace Ramstack.HtmxToolkit;
 
 /// <summary>
 /// Represents configuration for a specific major version of HTMX.
 /// </summary>
 public abstract class HtmxConfig
 {
+    private HtmlString? _json;
+
     /// <summary>
     /// Gets the configured HTMX major version.
     /// </summary>
@@ -23,10 +27,33 @@ internal HtmxConfig(HtmxTargetVersion version) =>
         TargetVersion = version;
 
     /// <summary>
-    /// Serializes this configuration to JSON.
+    /// Returns this configuration serialized as JSON,
+    /// cached and reused until the configuration changes.
+    /// </summary>
+    /// <returns>
+    /// An <see cref="HtmlString" /> containing the configuration serialized as JSON.
+    /// </returns>
+    internal HtmlString ToJson() =>
+        _json ??= new HtmlString(Serialize());
+
+    /// <summary>
+    /// Serializes this configuration to a JSON string.
     /// </summary>
     /// <returns>
-    /// A string containing this configuration serialized as JSON.
+    /// A JSON string representing this configuration.
     /// </returns>
-    internal abstract string ToJson();
+    protected abstract string Serialize();
+
+    /// <summary>
+    /// Assigns <paramref name="value" /> to <paramref name="field" /> and invalidates
+    /// the cached JSON so it is regenerated on the next serialization.
+    /// </summary>
+    /// <typeparam name="T">The type of the field.</typeparam>
+    /// <param name="field">The backing field to update.</param>
+    /// <param name="value">The value to assign.</param>
+    protected void SetField<T>(ref T field, T value)
+    {
+        field = value;
+        _json = null;
+    }
 }

src/Ramstack.HtmxToolkit/HtmxFetchModeJsonConverter.cs

@@ -17,13 +17,8 @@ internal sealed class HtmxFetchModeJsonConverter : JsonConverter<HtmxFetchMode?>
     /// <inheritdoc />
     public override void Write(Utf8JsonWriter writer, HtmxFetchMode? value, JsonSerializerOptions options)
     {
-        if (value is null)
-        {
-            writer.WriteNullValue();
-        }
-        else
-        {
-            writer.WriteStringValue(value.GetValueOrDefault().GetFetchModeValue());
-        }
+        // NOTE: value is never null here: null-valued properties are omitted
+        // by JsonIgnoreCondition.WhenWritingNull before this converter is invoked.
+        writer.WriteStringValue(value.GetValueOrDefault().GetFetchModeValue());
     }
 }

src/Ramstack.HtmxToolkit/HtmxHistoryModeJsonConverter.cs

@@ -21,24 +21,19 @@ internal sealed class HtmxHistoryModeJsonConverter : JsonConverter<HtmxHistoryMo
     /// <inheritdoc />
     public override void Write(Utf8JsonWriter writer, HtmxHistoryMode? value, JsonSerializerOptions options)
     {
-        if (value is null)
+        // NOTE: value is never null here: null-valued properties are omitted
+        // by JsonIgnoreCondition.WhenWritingNull before this converter is invoked.
+        switch (value.GetValueOrDefault())
         {
-            writer.WriteNullValue();
-        }
-        else
-        {
-            switch (value.GetValueOrDefault())
-            {
-                case HtmxHistoryMode.Enabled:
-                    writer.WriteBooleanValue(true);
-                    break;
-                case HtmxHistoryMode.Disabled:
-                    writer.WriteBooleanValue(false);
-                    break;
-                default:
-                    writer.WriteStringValue(s_reload);
-                    break;
-            }
+            case HtmxHistoryMode.Enabled:
+                writer.WriteBooleanValue(true);
+                break;
+            case HtmxHistoryMode.Disabled:
+                writer.WriteBooleanValue(false);
+                break;
+            default:
+                writer.WriteStringValue(s_reload);
+                break;
         }
     }
 }

src/Ramstack.HtmxToolkit/HtmxScrollBehaviorJsonConverter.cs

@@ -17,13 +17,8 @@ internal sealed class HtmxScrollBehaviorJsonConverter : JsonConverter<HtmxScroll
     /// <inheritdoc />
     public override void Write(Utf8JsonWriter writer, HtmxScrollBehavior? value, JsonSerializerOptions options)
     {
-        if (value is null)
-        {
-            writer.WriteNullValue();
-        }
-        else
-        {
-            writer.WriteStringValue(value.GetValueOrDefault().GetScrollBehaviorValue());
-        }
+        // NOTE: value is never null here: null-valued properties are omitted
+        // by JsonIgnoreCondition.WhenWritingNull before this converter is invoked.
+        writer.WriteStringValue(value.GetValueOrDefault().GetScrollBehaviorValue());
     }
 }

src/Ramstack.HtmxToolkit/HtmxSwapJsonConverter.cs

@@ -17,13 +17,8 @@ internal sealed class HtmxSwapJsonConverter : JsonConverter<HtmxSwap?>
     /// <inheritdoc />
     public override void Write(Utf8JsonWriter writer, HtmxSwap? value, JsonSerializerOptions options)
     {
-        if (value is null)
-        {
-            writer.WriteNullValue();
-        }
-        else
-        {
-            writer.WriteStringValue(value.GetValueOrDefault().GetSwapValue());
-        }
+        // NOTE: value is never null here: null-valued properties are omitted
+        // by JsonIgnoreCondition.WhenWritingNull before this converter is invoked.
+        writer.WriteStringValue(value.GetValueOrDefault().GetSwapValue());
     }
 }