fix(schema): remove Count==1 guard so works with siblings

Allows  schemas with annotation siblings (description, title,
, etc.) to still create an OpenApiSchemaReference with Target
resolution, matching how  already handles siblings.

Adds  parsing to the  branch, matching the  branch.

Author: aqeelat

src/Microsoft.OpenApi/Reader/V31/OpenApiSchemaDeserializer.cs

@@ -468,17 +468,22 @@ public static IOpenApiSchema LoadSchema(JsonNode node, OpenApiDocument hostDocum
             return result;
         }
 
-        if (dynamicPointer != null && jsonObject.Count == 1)
+        if (dynamicPointer != null)
         {
-            // A pure, bare $dynamicRef (no other schema keywords): create an OpenApiSchemaReference
-            // whose Target resolves via the $dynamicAnchor index instead of the $ref URI lookup.
-            // When siblings are present (type, properties, maxProperties, $defs, etc.) fall through to
-            // ParseMap so they are preserved on a normal OpenApiSchema instead of being dropped.
             var anchorName = JsonNodeHelper.ExtractDynamicAnchorName(dynamicPointer);
             var result = new OpenApiSchemaReference(!string.IsNullOrEmpty(anchorName) ? anchorName! : dynamicPointer, hostDocument);
             result.Reference.DynamicRef = dynamicPointer;
             result.Reference.IsDynamicRefOnly = true;
             result.Reference.SetMetadataFromJsonObject(jsonObject);
+
+            if (jsonObject.TryGetPropertyValue(OpenApiConstants.Defs, out var dynDefsNode) && dynDefsNode is JsonObject)
+            {
+                context.StartObject(OpenApiConstants.Defs);
+                if (dynDefsNode.CreateMap(LoadSchema, hostDocument, context) is { Count: > 0 } dynDefinitions)
+                    result.Reference.Definitions = dynDefinitions;
+                context.EndObject();
+            }
+
             return result;
         }
 

src/Microsoft.OpenApi/Reader/V32/OpenApiSchemaDeserializer.cs

@@ -468,17 +468,22 @@ public static IOpenApiSchema LoadSchema(JsonNode node, OpenApiDocument hostDocum
             return result;
         }
 
-        if (dynamicPointer != null && jsonObject.Count == 1)
+        if (dynamicPointer != null)
         {
-            // A pure, bare $dynamicRef (no other schema keywords): create an OpenApiSchemaReference
-            // whose Target resolves via the $dynamicAnchor index instead of the $ref URI lookup.
-            // When siblings are present (type, properties, maxProperties, $defs, etc.) fall through to
-            // ParseMap so they are preserved on a normal OpenApiSchema instead of being dropped.
             var anchorName = JsonNodeHelper.ExtractDynamicAnchorName(dynamicPointer);
             var result = new OpenApiSchemaReference(!string.IsNullOrEmpty(anchorName) ? anchorName! : dynamicPointer, hostDocument);
             result.Reference.DynamicRef = dynamicPointer;
             result.Reference.IsDynamicRefOnly = true;
             result.Reference.SetMetadataFromJsonObject(jsonObject);
+
+            if (jsonObject.TryGetPropertyValue(OpenApiConstants.Defs, out var dynDefsNode) && dynDefsNode is JsonObject)
+            {
+                context.StartObject(OpenApiConstants.Defs);
+                if (dynDefsNode.CreateMap(LoadSchema, hostDocument, context) is { Count: > 0 } dynDefinitions)
+                    result.Reference.Definitions = dynDefinitions;
+                context.EndObject();
+            }
+
             return result;
         }
 

test/Microsoft.OpenApi.Readers.Tests/V31Tests/OpenApiDynamicRefTests.cs

@@ -706,4 +706,75 @@ public async Task CreateShallowCopyPreservesValidationSiblings()
         Assert.NotNull(copy.AllOf);
         Assert.Single(copy.AllOf);
     }
+
+    [Fact]
+    public async Task DynamicRefWithAnnotationSiblingResolvesAndPreservesSibling()
+    {
+        var yaml =
+        """
+        openapi: 3.1.0
+        info:
+          title: Test
+          version: 1.0.0
+        paths: {}
+        components:
+          schemas:
+            Tree:
+              $dynamicAnchor: node
+              type: object
+              properties:
+                value:
+                  type: string
+                next:
+                  $dynamicRef: '#node'
+                  description: The next node in the tree
+        """;
+
+        var doc = await LoadDocumentAsync(yaml);
+
+        var tree = doc.Components.Schemas["Tree"];
+        var nextSchema = tree.Properties["next"];
+
+        var reference = Assert.IsType<OpenApiSchemaReference>(nextSchema);
+        Assert.True(reference.Reference.IsDynamicRefOnly);
+        Assert.NotNull(reference.Target);
+        Assert.Same(tree, reference.Target);
+        Assert.Equal("The next node in the tree", reference.Description);
+    }
+
+    [Fact]
+    public async Task DynamicRefWithDefsSiblingParsesDefs()
+    {
+        var yaml =
+        """
+        openapi: 3.1.0
+        info:
+          title: Test
+          version: 1.0.0
+        paths: {}
+        components:
+          schemas:
+            Tree:
+              $dynamicAnchor: node
+              type: object
+              properties:
+                next:
+                  $dynamicRef: '#node'
+                  $defs:
+                    extra:
+                      type: string
+        """;
+
+        var doc = await LoadDocumentAsync(yaml);
+
+        var tree = doc.Components.Schemas["Tree"];
+        var nextSchema = tree.Properties["next"];
+
+        var reference = Assert.IsType<OpenApiSchemaReference>(nextSchema);
+        Assert.True(reference.Reference.IsDynamicRefOnly);
+        Assert.NotNull(reference.Target);
+        Assert.Same(tree, reference.Target);
+        Assert.NotNull(reference.Definitions);
+        Assert.True(reference.Definitions.ContainsKey("extra"));
+    }
 }