Add IndentText json option

src/libraries/System.Text.Json/ref/System.Text.Json.cs

@@ -394,6 +394,7 @@ public JsonSerializerOptions(System.Text.Json.JsonSerializerOptions options) { }
         public System.Text.Json.Serialization.JsonUnknownTypeHandling UnknownTypeHandling { get { throw null; } set { } }
         public System.Text.Json.Serialization.JsonUnmappedMemberHandling UnmappedMemberHandling { get { throw null; } set { } }
         public bool WriteIndented { get { throw null; } set { } }
+        public string? IndentText { get { throw null; } set { } }
         [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
         [System.ObsoleteAttribute("JsonSerializerOptions.AddContext is obsolete. To register a JsonSerializerContext, use either the TypeInfoResolver or TypeInfoResolverChain properties.", DiagnosticId="SYSLIB0049", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
         public void AddContext<TContext>() where TContext : System.Text.Json.Serialization.JsonSerializerContext, new() { }
@@ -439,6 +440,7 @@ public partial struct JsonWriterOptions
         private int _dummyPrimitive;
         public System.Text.Encodings.Web.JavaScriptEncoder? Encoder { readonly get { throw null; } set { } }
         public bool Indented { get { throw null; } set { } }
+        public string? IndentText { get { throw null; } set { } }
         public int MaxDepth { readonly get { throw null; } set { } }
         public bool SkipValidation { get { throw null; } set { } }
     }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Caching.cs

@@ -511,6 +511,7 @@ public bool Equals(JsonSerializerOptions? left, JsonSerializerOptions? right)
                     left._includeFields == right._includeFields &&
                     left._propertyNameCaseInsensitive == right._propertyNameCaseInsensitive &&
                     left._writeIndented == right._writeIndented &&
+                    left._indentText == right._indentText &&
                     left._typeInfoResolver == right._typeInfoResolver &&
                     CompareLists(left._converters, right._converters);
 
@@ -565,6 +566,7 @@ public int GetHashCode(JsonSerializerOptions options)
                 AddHashCode(ref hc, options._includeFields);
                 AddHashCode(ref hc, options._propertyNameCaseInsensitive);
                 AddHashCode(ref hc, options._writeIndented);
+                AddHashCode(ref hc, options._indentText?.GetHashCode() ?? 0);
                 AddHashCode(ref hc, options._typeInfoResolver);
                 AddListHashCode(ref hc, options._converters);
 

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.cs

@@ -75,6 +75,7 @@ public static JsonSerializerOptions Default
         private bool _includeFields;
         private bool _propertyNameCaseInsensitive;
         private bool _writeIndented;
+        private string? _indentText;
 
         /// <summary>
         /// Constructs a new <see cref="JsonSerializerOptions"/> instance.
@@ -124,6 +125,7 @@ public JsonSerializerOptions(JsonSerializerOptions options)
             _includeFields = options._includeFields;
             _propertyNameCaseInsensitive = options._propertyNameCaseInsensitive;
             _writeIndented = options._writeIndented;
+            _indentText = options._indentText;
             _typeInfoResolver = options._typeInfoResolver;
             EffectiveMaxDepth = options.EffectiveMaxDepth;
             ReferenceHandlingStrategy = options.ReferenceHandlingStrategy;
@@ -645,6 +647,27 @@ public bool WriteIndented
             }
         }
 
+        /// <summary>
+        /// Defines the text used as indent when <see cref="WriteIndented" /> is enabled
+        /// By default, the JSON is indented with 2 white spaces.
+        /// </summary>
+        /// <exception cref="InvalidOperationException">
+        /// Thrown if this property is set after serialization or deserialization has occurred.
+        /// </exception>
+        public string? IndentText
+        {
+            get
+            {
+                return _indentText;
+            }
+            set
+            {
+                VerifyMutable();
+                // Validation?
+                _indentText = value;
+            }
+        }
+
         /// <summary>
         /// Configures how object references are handled when reading and writing JSON.
         /// </summary>
@@ -876,6 +899,7 @@ internal JsonWriterOptions GetWriterOptions()
             {
                 Encoder = Encoder,
                 Indented = WriteIndented,
+                IndentText = IndentText,
                 MaxDepth = EffectiveMaxDepth,
 #if !DEBUG
                 SkipValidation = true

src/libraries/System.Text.Json/src/System/Text/Json/Writer/JsonWriterHelper.cs

@@ -32,6 +32,18 @@ public static void WriteIndentation(Span<byte> buffer, int indent)
             }
         }
 
+        public static void WriteIndentation(Span<byte> buffer, int indentation, Span<byte> indent)
+        {
+            Debug.Assert(buffer.Length >= indentation);
+
+            int offset = 0;
+            while (offset < indentation)
+            {
+                indent.CopyTo(buffer.Slice(offset));
+                offset += indent.Length;
+            }
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void ValidateProperty(ReadOnlySpan<byte> propertyName)
         {

src/libraries/System.Text.Json/src/System/Text/Json/Writer/JsonWriterOptions.cs

@@ -17,6 +17,7 @@ public struct JsonWriterOptions
 
         private int _maxDepth;
         private int _optionsMask;
+        private string? _indentText;
 
         /// <summary>
         /// The encoder to use when escaping strings, or <see langword="null" /> to use the default encoder.
@@ -43,6 +44,20 @@ public bool Indented
             }
         }
 
+        /// <summary>
+        /// Defines the text used as indent by the <see cref="Utf8JsonWriter"/> when <see cref="Indented"/> is enabled
+        /// By default, the JSON is written with 2 white spaces.
+        /// </summary>
+        public string? IndentText
+        {
+            get => _indentText;
+            set
+            {
+                // Validation?
+                _indentText = value;
+            }
+        }
+
         /// <summary>
         /// Gets or sets the maximum depth allowed when writing JSON, with the default (i.e. 0) indicating a max depth of 1000.
         /// </summary>

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.Bytes.cs

@@ -309,7 +309,7 @@ private void WriteBase64Indented(ReadOnlySpan<char> escapedPropertyName, ReadOnl
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -359,7 +359,7 @@ private void WriteBase64Indented(ReadOnlySpan<byte> escapedPropertyName, ReadOnl
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.DateTime.cs

@@ -311,7 +311,7 @@ private void WriteStringIndented(ReadOnlySpan<char> escapedPropertyName, DateTim
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -359,7 +359,7 @@ private void WriteStringIndented(ReadOnlySpan<byte> escapedPropertyName, DateTim
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.DateTimeOffset.cs

@@ -310,7 +310,7 @@ private void WriteStringIndented(ReadOnlySpan<char> escapedPropertyName, DateTim
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -358,7 +358,7 @@ private void WriteStringIndented(ReadOnlySpan<byte> escapedPropertyName, DateTim
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.Decimal.cs

@@ -304,7 +304,7 @@ private void WriteNumberIndented(ReadOnlySpan<char> escapedPropertyName, decimal
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -349,7 +349,7 @@ private void WriteNumberIndented(ReadOnlySpan<byte> escapedPropertyName, decimal
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.Double.cs

@@ -308,7 +308,7 @@ private void WriteNumberIndented(ReadOnlySpan<char> escapedPropertyName, double
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -353,7 +353,7 @@ private void WriteNumberIndented(ReadOnlySpan<byte> escapedPropertyName, double
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.Float.cs

@@ -308,7 +308,7 @@ private void WriteNumberIndented(ReadOnlySpan<char> escapedPropertyName, float v
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -353,7 +353,7 @@ private void WriteNumberIndented(ReadOnlySpan<byte> escapedPropertyName, float v
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.Guid.cs

@@ -312,7 +312,7 @@ private void WriteStringIndented(ReadOnlySpan<char> escapedPropertyName, Guid va
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -361,7 +361,7 @@ private void WriteStringIndented(ReadOnlySpan<byte> escapedPropertyName, Guid va
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.Helpers.cs

@@ -115,7 +115,7 @@ private void WritePropertyNameIndented(ReadOnlySpan<byte> escapedPropertyName, b
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -188,7 +188,7 @@ private void WritePropertyNameIndented(ReadOnlySpan<char> escapedPropertyName, b
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.Literal.cs

@@ -455,7 +455,7 @@ private void WriteLiteralIndented(ReadOnlySpan<char> escapedPropertyName, ReadOn
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -500,7 +500,7 @@ private void WriteLiteralIndented(ReadOnlySpan<byte> escapedPropertyName, ReadOn
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.SignedNumber.cs

@@ -380,7 +380,7 @@ private void WriteNumberIndented(ReadOnlySpan<char> escapedPropertyName, long va
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -425,7 +425,7 @@ private void WriteNumberIndented(ReadOnlySpan<byte> escapedPropertyName, long va
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.String.cs

@@ -213,7 +213,7 @@ private void WriteStringIndentedPropertyName(ReadOnlySpan<char> escapedPropertyN
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -402,7 +402,7 @@ private void WriteStringIndentedPropertyName(ReadOnlySpan<byte> escapedPropertyN
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -1541,7 +1541,7 @@ private void WriteStringIndented(ReadOnlySpan<char> escapedPropertyName, ReadOnl
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -1590,7 +1590,7 @@ private void WriteStringIndented(ReadOnlySpan<byte> escapedPropertyName, ReadOnl
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -1642,7 +1642,7 @@ private void WriteStringIndented(ReadOnlySpan<char> escapedPropertyName, ReadOnl
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -1693,7 +1693,7 @@ private void WriteStringIndented(ReadOnlySpan<byte> escapedPropertyName, ReadOnl
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteProperties.UnsignedNumber.cs

@@ -389,7 +389,7 @@ private void WriteNumberIndented(ReadOnlySpan<char> escapedPropertyName, ulong v
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;
@@ -434,7 +434,7 @@ private void WriteNumberIndented(ReadOnlySpan<byte> escapedPropertyName, ulong v
                 WriteNewLine(output);
             }
 
-            JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+            WriteIndentation(output.Slice(BytesPending), indent);
             BytesPending += indent;
 
             output[BytesPending++] = JsonConstants.Quote;

src/libraries/System.Text.Json/src/System/Text/Json/Writer/Utf8JsonWriter.WriteValues.Bytes.cs

@@ -124,7 +124,7 @@ private void WriteBase64Indented(ReadOnlySpan<byte> bytes)
                 {
                     WriteNewLine(output);
                 }
-                JsonWriterHelper.WriteIndentation(output.Slice(BytesPending), indent);
+                WriteIndentation(output.Slice(BytesPending), indent);
                 BytesPending += indent;
             }