chore: change JavascriptEncoder settings and add related tests

Author: filzrev

src/Docfx.Common/Json/System.Text.Json/SystemTextJsonUtility.cs

@@ -33,7 +33,7 @@ static SystemTextJsonUtility()
             // DefaultBufferSize = 1024 * 16, // TODO: Set appropriate buffer size based on benchmark.(Default: 16KB)
             AllowTrailingCommas = true,
             DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
-            // Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping, // Some chars are escaped by this settings (e.g. `+`, `　`(full width space)
+            Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping, // TODO: Replace with custom encoder that encode minimal chars (https://github.com/dotnet/runtime/issues/87153)
             PropertyNameCaseInsensitive = true,
             PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
             // DictionaryKeyPolicy = JsonNamingPolicy.CamelCase, // This setting is not compatible to `Newtonsoft.Json` serialize result.

test/docfx.Tests/SerializationTests/JsonSerializationEncoderTest.cs

@@ -0,0 +1,56 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Docfx.Common;
+using FluentAssertions;
+
+namespace docfx.Tests;
+
+public partial class JsonSerializationEncoderTest
+{
+    [Theory]
+    [InlineData("abcdefghighlmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")]
+    [InlineData("0123456789")]
+    [InlineData("\0\a\b\t\n\v\f\r\e")]
+    [InlineData("!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~")]
+    [InlineData("①②③")] // NonAscii chars (Enclosed Alphanumerics)
+    [InlineData("１２３")] // NonAscii chars (Full-width digits)
+    [InlineData("äöü")]   // Umlaut
+    [InlineData("漢字")]   // Kanji
+    public void JsonEncoderTest(string data)
+    {
+        // Arrange
+        var model = data;
+
+        //Act
+        var systemTextJsonResult = SystemTextJsonUtility.Serialize(model);
+        var newtonsoftJsonResult = NewtonsoftJsonUtility.Serialize(model);
+
+        // Assert
+        // Compare serialized result text with `StringComparer.OrdinalIgnoreCase`
+        //  - SystemTextJson escape chars with capital case(`\u001B`)
+        //  - NewtonsoftJson escape chars with lower case  (`\u001b`)
+        ((object)systemTextJsonResult).Should().Be(newtonsoftJsonResult, StringComparer.OrdinalIgnoreCase); // Currently StringAssertions don't expose overload that accepts StringComparer. (See: https://github.com/fluentassertions/fluentassertions/issues/2720)
+    }
+
+    [Theory]
+    [InlineData("　", @"\u3000")]                                 // Full-Width space (Excaped by global block list (https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/character-encoding#global-block-list))
+    [InlineData("𠮟", @"\uD842\uDF9F")]                           // Kanji (that use Surrogate Pair)
+    [InlineData("📄", @"\uD83D\uDCC4")]                          // Emoji
+    [InlineData("👁‍🗨", @"\uD83D\uDC41‍\uD83D\uDDE8")] // Emoji (with ZWJ (ZERO WIDTH JOINER))
+    public void JsonEncoderTest_NoCompatibility(string data, string expected)
+    {
+        // Arrange
+        var model = data;
+
+        //Act
+        var systemTextJsonResult = SystemTextJsonUtility.Serialize(model);
+        var newtonsoftJsonResult = NewtonsoftJsonUtility.Serialize(model);
+
+        // Assert
+        systemTextJsonResult.Should().NotBe(newtonsoftJsonResult);
+
+        systemTextJsonResult.Should().Contain(expected);
+        newtonsoftJsonResult.Should().Contain(data);
+    }
+}