Add JsonWriterOptions to TemplateOptions and TemplateContext (#846)

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: sebastienros <[email protected]>
Co-authored-by: Sébastien Ros <[email protected]>

Author: Copilot

Fluid.Tests/MiscFiltersTests.cs

@@ -5,6 +5,7 @@
 using System.Globalization;
 using System.Linq;
 using System.Text.Encodings.Web;
+using System.Text.Json;
 using System.Threading.Tasks;
 using TimeZoneConverter;
 using Xunit;
@@ -823,6 +824,60 @@ public async Task JsonShouldUseJsonSerializerOption()
             Assert.Equal(expected, result.ToStringValue());
         }
 
+        [Fact]
+        public async Task JsonShouldUseJsonWriterOptionsFromTemplateOptions()
+        {
+            var options = new TemplateOptions
+            {
+                JsonWriterOptions = new JsonWriterOptions
+                {
+                    Indented = true
+                }
+            };
+
+            var input = FluidValue.Create(new { name = "test", value = 123 }, options);
+            options.MemberAccessStrategy.Register(input.ToObjectValue().GetType());
+            var context = new TemplateContext(options);
+            var result = await MiscFilters.Json(input, new FilterArguments(), context);
+
+            // Indented JSON should have newlines
+            Assert.Contains("\n", result.ToStringValue());
+        }
+
+        [Fact]
+        public async Task JsonShouldUseJsonWriterOptionsFromTemplateContext()
+        {
+            var options = new TemplateOptions();
+            var context = new TemplateContext(options)
+            {
+                JsonWriterOptions = new JsonWriterOptions
+                {
+                    Indented = true
+                }
+            };
+
+            var input = FluidValue.Create(new { name = "test", value = 123 }, options);
+            options.MemberAccessStrategy.Register(input.ToObjectValue().GetType());
+            var result = await MiscFilters.Json(input, new FilterArguments(), context);
+
+            // Indented JSON should have newlines
+            Assert.Contains("\n", result.ToStringValue());
+        }
+
+        [Fact]
+        public async Task JsonShouldSerializeEnumsAsNumbers()
+        {
+            var options = new TemplateOptions();
+            options.MemberAccessStrategy.Register<TestEnum>();
+            
+            var input = FluidValue.Create(TestEnum.Value2, options);
+            var context = new TemplateContext(options);
+            var result = await MiscFilters.Json(input, new FilterArguments(), context);
+
+            // Enum should be serialized as number (1 for Value2)
+            Assert.Equal("1", result.ToStringValue());
+        }
+
         [Theory]
         [InlineData("", "", "", "0")]
         [InlineData(123456, "", "", "123456")]
@@ -1029,5 +1084,12 @@ public DictionaryWithoutIndexableTestObjects(object value) : base(value)
 
             }
         }
+
+        private enum TestEnum
+        {
+            Value1 = 0,
+            Value2 = 1,
+            Value3 = 2
+        }
     }
 }

Fluid/Filters/MiscFilters.cs

@@ -792,10 +792,8 @@ private static async ValueTask WriteJson(Utf8JsonWriter writer, FluidValue input
         public static async ValueTask<FluidValue> Json(FluidValue input, FilterArguments arguments, TemplateContext context)
         {
             using var ms = new MemoryStream();
-            await using (var writer = new Utf8JsonWriter(ms, new JsonWriterOptions
-            {
-                Indented = arguments.At(0).ToBooleanValue()
-            }))
+            
+            await using (var writer = new Utf8JsonWriter(ms, context.JsonWriterOptions))
             {
                 await WriteJson(writer, input, context);
             }

Fluid/TemplateContext.cs

@@ -1,6 +1,7 @@
 using Fluid.Values;
 using System.Globalization;
 using System.Runtime.CompilerServices;
+using System.Text.Json;
 
 namespace Fluid
 {
@@ -59,6 +60,7 @@ public TemplateContext(TemplateOptions options, StringComparer modelNamesCompare
             Now = options.Now;
             MaxSteps = options.MaxSteps;
             ModelNamesComparer = modelNamesComparer;
+            JsonWriterOptions = options.JsonWriterOptions;
         }
 
         /// <summary>
@@ -115,6 +117,11 @@ public TemplateContext(object model, bool allowModelMembers = true, StringCompar
         /// </summary>
         public TimeZoneInfo TimeZone { get; set; } = TemplateOptions.Default.TimeZone;
 
+        /// <summary>
+        /// Gets or sets the <see cref="JsonWriterOptions"/> used by the <c>json</c> filter.
+        /// </summary>
+        public JsonWriterOptions JsonWriterOptions { get; set; } = TemplateOptions.Default.JsonWriterOptions;
+
         /// <summary>
         /// Increments the number of statements the current template is processing.
         /// </summary>

Fluid/TemplateOptions.cs

@@ -3,6 +3,7 @@
 using Microsoft.Extensions.FileProviders;
 using System.Globalization;
 using System.Text.Encodings.Web;
+using System.Text.Json;
 
 namespace Fluid
 {
@@ -105,6 +106,11 @@ public class TemplateOptions
         /// </summary>
         public JavaScriptEncoder JavaScriptEncoder { get; set; } = DefaultJavaScriptEncoder;
 
+        /// <summary>
+        /// Gets or sets the <see cref="JsonWriterOptions"/> used by the <c>json</c> filter.
+        /// </summary>
+        public JsonWriterOptions JsonWriterOptions { get; set; } = new JsonWriterOptions();
+
         /// <summary>
         /// Gets or sets the default trimming rules.
         /// </summary>

README.md

@@ -366,6 +366,48 @@ var context = new TemplateContext(options);
 "你好，这是一条短信"
 ```
 
+### Customizing JSON output
+
+The `json` filter uses `System.Text.Json.JsonWriterOptions` to control the JSON output format. You can customize these options through `TemplateOptions.JsonWriterOptions` or `TemplateContext.JsonWriterOptions`.
+
+#### Example: Indented JSON output
+
+```csharp
+var options = new TemplateOptions
+{
+    JsonWriterOptions = new JsonWriterOptions
+    {
+        Indented = true
+    }
+};
+
+var context = new TemplateContext(options);
+context.SetValue("data", new { name = "John", age = 30 });
+```
+
+```Liquid
+{{ data | json }}
+```
+
+#### Result
+```json
+{
+  "name": "John",
+  "age": 30
+}
+```
+
+You can also set `JsonWriterOptions` per context:
+
+```csharp
+var context = new TemplateContext();
+context.JsonWriterOptions = new JsonWriterOptions
+{
+    Indented = true,
+    // Other options like MaxDepth, SkipValidation, etc.
+};
+```
+
 <br>
 
 ## Localization