fix(library): avoid false circular refs for external schema re-exports

src/Microsoft.OpenApi/Services/OpenApiWorkspace.cs

@@ -81,7 +81,7 @@
         /// Registers a document's components into the workspace
         /// </summary>
         /// <param name="document"></param>
         public void RegisterComponents(OpenApiDocument document)
         {
             if (document?.Components == null) return;
 
@@ -94,8 +94,13 @@
                 foreach (var item in document.Components.Schemas)
                 {
                     if (item.Value == null) continue;
-                    location = item.Value.Id ?? baseUri + ReferenceType.Schema.GetDisplayName() + ComponentSegmentSeparator + item.Key;
+                    location = baseUri + ReferenceType.Schema.GetDisplayName() + ComponentSegmentSeparator + item.Key;
                     RegisterComponent(location, item.Value);
+
+                    if (item.Value is not OpenApiSchemaReference && item.Value.Id is string schemaId && schemaId.Length > 0)
+                    {
+                        RegisterComponent(schemaId, item.Value);
+                    }
                 }
             }
 
@@ -290,7 +295,7 @@
         /// <param name="value"></param>
         public void AddDocumentId(string? key, Uri? value)
         {
             if (!string.IsNullOrEmpty(key) && key is not null && value is not null && !_documentsIdRegistry.ContainsKey(key))
             {
                 _documentsIdRegistry[key] = value;
             }
@@ -393,7 +398,7 @@
             return default;          
         }
 
         internal static IOpenApiSchema? ResolveSubSchema(IOpenApiSchema schema, string[] pathSegments, Stack<IOpenApiSchema> visitedSchemas)
         {
             // Prevent infinite recursion in case of circular references
             if (visitedSchemas.Contains(schema))

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

@@ -203,6 +203,75 @@ public async Task ParseLocalReferenceToJsonSchemaResourceWorks()
             Assert.Equal(JsonSchemaType.Object | JsonSchemaType.Null, schema.Type);
         }
 
+        [Fact]
+        public async Task ParseExternalSchemaReferencedDirectlyAndReExportedAtRootWorks()
+        {
+            var tempDirectory = Path.Join(Path.GetTempPath(), Guid.NewGuid().ToString("N"));
+            Directory.CreateDirectory(tempDirectory);
+
+            var rootPath = Path.Join(tempDirectory, "root.yaml");
+            var sharedPath = Path.Join(tempDirectory, "shared.yaml");
+
+            await File.WriteAllTextAsync(rootPath,
+            @"openapi: 3.1.0
+info:
+  title: T
+  version: 1.0.0
+paths:
+  /a:
+    get:
+      responses:
+        '200':
+          description: ok
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  meta:
+                    $ref: './shared.yaml#/Leaf'
+components:
+  schemas:
+    Leaf:
+      $ref: './shared.yaml#/Leaf'
+");
+
+            await File.WriteAllTextAsync(sharedPath,
+            @"Leaf:
+  type: object
+  properties:
+    x:
+      type: string
+    y:
+      type: integer
+");
+
+            try
+            {
+                var settings = new OpenApiReaderSettings
+                {
+                    LoadExternalRefs = true,
+                    BaseUrl = new Uri(rootPath),
+                };
+                settings.AddYamlReader();
+
+                var result = await OpenApiDocument.LoadAsync(rootPath, settings);
+                var responseSchema = result.Document.Paths["/a"].Operations[HttpMethod.Get].Responses["200"].Content["application/json"].Schema;
+                var metaSchema = responseSchema.Properties["meta"];
+                var leafSchema = result.Document.Components.Schemas["Leaf"];
+
+                Assert.NotNull(result.Document);
+                Assert.DoesNotContain(result.Diagnostic.Errors, error => error.Message.Contains("Circular reference detected while resolving schema", StringComparison.Ordinal));
+                Assert.DoesNotContain(result.Diagnostic.Warnings, warning => warning.Message.Contains("Circular reference detected while resolving schema", StringComparison.Ordinal));
+                Assert.IsType<OpenApiSchemaReference>(metaSchema);
+                Assert.IsType<OpenApiSchemaReference>(leafSchema);
+            }
+            finally
+            {
+                Directory.Delete(tempDirectory, true);
+            }
+        }
+
         [Fact]
         public void ResolveSubSchema_ShouldTraverseKnownKeywords()
         {