fix: an issue where numeric property names would be missing quotes in yaml conversion

Signed-off-by: Vincent Biret <[email protected]>

Author: baywet

src/Microsoft.OpenApi.YamlReader/YamlConverter.cs

@@ -87,7 +87,10 @@ public static JsonObject ToJsonObject(this YamlMappingNode yaml)
 
         private static YamlMappingNode ToYamlMapping(this JsonObject obj)
         {
-            return new YamlMappingNode(obj.ToDictionary(x => (YamlNode)new YamlScalarNode(x.Key), x => x.Value!.ToYamlNode()));
+            return new YamlMappingNode(obj.ToDictionary(x => (YamlNode)new YamlScalarNode(x.Key)
+            {
+                Style = double.TryParse(x.Key, out _) ? ScalarStyle.DoubleQuoted : ScalarStyle.Plain
+            }, x => x.Value!.ToYamlNode()));
         }
 
         /// <summary>

test/Microsoft.OpenApi.Readers.Tests/YamlConverterTests.cs

@@ -1,4 +1,5 @@
-using Microsoft.OpenApi.YamlReader;
+using Microsoft.OpenApi.Tests;
+using Microsoft.OpenApi.YamlReader;
 using SharpYaml;
 using SharpYaml.Serialization;
 using System.IO;
@@ -225,12 +226,60 @@ public void ToYamlNode_StringWithLineBreaks_PreservesLineBreaks()
         Assert.Contains("\n", roundTripDescription);
     }
 
+    [Fact]
+    public void NumericPropertyNamesShouldRemainStringsFromJson()
+    {
+        // Given
+        var yamlInput =
+        """
+        "123": value1
+        "456": value2
+        """;
+
+        // Given
+        var jsonNode = Assert.IsType<JsonObject>(JsonNode.Parse(@"{
+            ""123"": ""value1"",
+            ""456"": ""value2""
+        }"));
+
+        // When
+        var convertedBack = jsonNode.ToYamlNode();
+        var convertedBackOutput = ConvertYamlNodeToString(convertedBack);
+
+        // Then
+        Assert.Equal(yamlInput.MakeLineBreaksEnvironmentNeutral(), convertedBackOutput.MakeLineBreaksEnvironmentNeutral());
+    }
+
+    [Fact]
+    public void NumericPropertyNamesShouldRemainStringsFromYaml()
+    {
+        // Given
+        var yamlInput =
+        """
+        "123": value1
+        "456": value2
+        """;
+
+        var yamlDocument = new YamlStream();
+        using var sr = new StringReader(yamlInput);
+        yamlDocument.Load(sr);
+        var yamlRoot = yamlDocument.Documents[0].RootNode;
+        // When
+
+        var jsonNode = yamlRoot.ToJsonNode();
+
+        var convertedBack = jsonNode.ToYamlNode();
+        var convertedBackOutput = ConvertYamlNodeToString(convertedBack);
+        // Then
+        Assert.Equal(yamlInput.MakeLineBreaksEnvironmentNeutral(), convertedBackOutput.MakeLineBreaksEnvironmentNeutral());
+    }
+
     private static string ConvertYamlNodeToString(YamlNode yamlNode)
     {
         using var ms = new MemoryStream();
-        var yamlStream = new YamlStream(new YamlDocument(yamlNode));
+        var document = new YamlStream(new YamlDocument(yamlNode));
         var writer = new StreamWriter(ms);
-        yamlStream.Save(writer);
+        document.Save(writer, isLastDocumentEndImplicit: true);
         writer.Flush();
         ms.Seek(0, SeekOrigin.Begin);
         var reader = new StreamReader(ms);