Problem

The YamlConverter.ToYamlNode() method was adding extra quotes to string values when converting from JSON to YAML, causing incorrect output:

var json = JsonNode.Parse(@"{
   ""fooString"": ""fooStringValue"",
   ""fooStringOfNumber"": ""200""
}");

var yamlNode = json.ToYamlNode();
// Writes to YAML...

Previous (Incorrect) Output:

fooString: '"fooStringValue"'
fooStringOfNumber: '"200"'

Expected Output:

fooString: fooStringValue
fooStringOfNumber: "200"

Root Cause

The ToYamlScalar method was using JsonValue.ToJsonString() to extract values. This method returns the JSON representation of a value, which includes quotes around strings. When these quoted strings were passed to YamlScalarNode, the YAML serializer treated the quotes as part of the actual string content and escaped them, resulting in double-quoted output.

Solution

Modified ToYamlScalar to:

1. Extract actual values using TryGetValue<string>() instead of ToJsonString() to get the underlying value without JSON formatting
2. Apply intelligent quoting based on value type:
   • Regular strings (e.g., "fooStringValue") → output unquoted as fooStringValue
   • Strings that look like numbers/booleans/null (e.g., "200", "true", "null") → output quoted as "200", "true", "null" to preserve type information during round-tripping
   • Strings with line breaks → automatically quoted to preserve formatting
   • Actual numbers and booleans → output unquoted as 200, true

This ensures proper type preservation when converting between JSON and YAML while producing clean, readable YAML output.

Testing

Added 11 comprehensive unit tests covering:

• Regular strings (should be unquoted)
• Strings that look like numbers (should be quoted to preserve string type)
• Actual numeric values (should be unquoted)
• Strings that look like booleans (should be quoted)
• Actual boolean values (should be unquoted)
• Strings that look like null (should be quoted)
• Mixed type documents
• The exact scenario from the issue report
• Strings with line breaks (should preserve line breaks during round-tripping)

All existing tests continue to pass with no regressions.

Fixes #1951

Fixes #2561

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