Add JavaScriptEncoder option (#739)

Fixes #737

Fluid.Tests/MiscFiltersTests.cs

@@ -1,10 +1,11 @@
-using System;
-using System.Globalization;
-using System.Linq;
-using System.Threading.Tasks;
 using Fluid.Filters;
 using Fluid.Values;
 using Newtonsoft.Json.Linq;
+using System;
+using System.Globalization;
+using System.Linq;
+using System.Text.Encodings.Web;
+using System.Threading.Tasks;
 using TimeZoneConverter;
 using Xunit;
 
@@ -779,6 +780,29 @@ public async Task JsonShouldWriteValuesWithCorrectDataTypeForJObjectInput()
             Assert.Equal(expected, result.ToStringValue());
         }
 
+        [Fact]
+        public async Task JsonShouldEncodeUnicodeChars()
+        {
+            var input = FluidValue.Create("你好，这是一条短信", TemplateOptions.Default);
+            var result = await MiscFilters.Json(input, new FilterArguments(), new TemplateContext(TemplateOptions.Default));
+            var expected = @"""\u4F60\u597D\uFF0C\u8FD9\u662F\u4E00\u6761\u77ED\u4FE1""";
+            Assert.Equal(expected, result.ToStringValue());
+        }
+
+        [Fact]
+        public async Task JsonShouldUseJsonSerializerOption()
+        {
+            var options = new TemplateOptions
+            {
+                JavaScriptEncoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping
+            };
+
+            var input = FluidValue.Create("你好，这是一条短信", options);
+            var result = await MiscFilters.Json(input, new FilterArguments(), new TemplateContext(options));
+            var expected = @"""你好，这是一条短信""";
+            Assert.Equal(expected, result.ToStringValue());
+        }
+
         [Theory]
         [InlineData("", "", "", "0")]
         [InlineData(123456, "", "", "123456")]

Fluid/Filters/MiscFilters.cs

@@ -774,7 +774,7 @@ private static async ValueTask WriteJson(Utf8JsonWriter writer, FluidValue input
                     }
                     break;
                 case FluidValues.String:
-                    writer.WriteStringValue(input.ToStringValue());
+                    writer.WriteStringValue(JsonEncodedText.Encode(input.ToStringValue(), ctx.Options.JavaScriptEncoder));
                     break;
                 case FluidValues.Blank:
                     writer.WriteStringValue(string.Empty);

Fluid/TemplateOptions.cs

@@ -2,6 +2,8 @@
 using Fluid.Values;
 using Microsoft.Extensions.FileProviders;
 using System.Globalization;
+using System.Text.Encodings.Web;
+using System.Text.Json;
 
 namespace Fluid
 {
@@ -21,6 +23,8 @@ public class TemplateOptions
 
         public static readonly TemplateOptions Default = new();
 
+        private static readonly JavaScriptEncoder DefaultJavaScriptEncoder = JavaScriptEncoder.Default;
+
         /// <summary>
         /// Gets ot sets the members than can be accessed in a template.
         /// </summary>
@@ -89,6 +93,11 @@ public class TemplateOptions
         /// </summary>
         public AssignedDelegate Assigned { get; set; }
 
+        /// <summary>
+        /// Gets or sets the <see cref="JavaScriptEncoder" /> instance used by the <c>json</c> filter.
+        /// </summary>
+        public JavaScriptEncoder JavaScriptEncoder { get; set; } = DefaultJavaScriptEncoder;
+
         /// <summary>
         /// Gets or sets the default trimming rules.
         /// </summary>
@@ -99,7 +108,6 @@ public class TemplateOptions
         /// </summary>
         public bool Greedy { get; set; } = true;
 
-
         public TemplateOptions()
         {
             Filters.WithArrayFilters()

README.md

@@ -335,16 +335,35 @@ Not encoded: {{ html | raw }
 When using `capture` blocks, the inner content is flagged as 
 pre-encoded and won't be double-encoded if used in a `{{ }}` tag.
 
-#### Source
+### JSON encoding
+
+By default all JSON strings are encoded using the default `JavaScriptEncoder` instance. This can be changed by setting the `TemplateOptions.JavaScriptEncoder` property.
+
 ```Liquid
-{% capture breaktag %}<br />{% endcapture %}
+{{ "你好，这是一条短信" | json" }}
+```
+
+#### Result
+
+```html
+"\u4F60\u597D\uFF0C\u8FD9\u662F\u4E00\u6761\u77ED\u4FE1"
+```
 
-{{ breaktag }}
+Using the `JavaScriptEncoder.UnsafeRelaxedJsonEscaping` can be done this way:
+
+```csharp
+// This variable should be static and reused for all templates
+var options = new TemplateOptions
+{
+    JavaScriptEncoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping
+};
+
+var context = new TemplateContext(options);
 ```
 
 #### Result
 ```html
-<br />
+"你好，这是一条短信"
 ```
 
 <br>