fix: anchor combination with id resolution

Author: baywet

src/Microsoft.OpenApi/Services/OpenApiWorkspace.cs

@@ -298,6 +298,13 @@ private void RegisterSchemaIdentifiers(IOpenApiSchema schema, Uri baseUri, ISet<
             }
 
             var schemaBaseUri = baseUri;
+            if (!string.IsNullOrEmpty(schema.Id) &&
+                Uri.TryCreate(schema.Id, UriKind.RelativeOrAbsolute, out var schemaIdUri))
+            {
+                schemaBaseUri = schemaIdUri.IsAbsoluteUri ? schemaIdUri : new Uri(baseUri, schemaIdUri);
+                RegisterComponent(schemaBaseUri.AbsoluteUri, schema);
+            }
+
             if (schema is IOpenApiSchemaMissingProperties { Anchor.Length: > 0 } schemaWithAnchor)
             {
                 var anchorUriBuilder = new UriBuilder(schemaBaseUri)
@@ -307,13 +314,6 @@ private void RegisterSchemaIdentifiers(IOpenApiSchema schema, Uri baseUri, ISet<
                 RegisterComponent(anchorUriBuilder.Uri.AbsoluteUri, schema);
             }
 
-            if (!string.IsNullOrEmpty(schema.Id) &&
-                Uri.TryCreate(schema.Id, UriKind.RelativeOrAbsolute, out var schemaIdUri))
-            {
-                schemaBaseUri = schemaIdUri.IsAbsoluteUri ? schemaIdUri : new Uri(baseUri, schemaIdUri);
-                RegisterComponent(schemaBaseUri.AbsoluteUri, schema);
-            }
-
             RegisterSchemaIdentifier(schema.Items, schemaBaseUri, visitedSchemas);
             RegisterSchemaIdentifier(schema.AdditionalProperties, schemaBaseUri, visitedSchemas);
             RegisterSchemaIdentifier(schema.Not, schemaBaseUri, visitedSchemas);

test/Microsoft.OpenApi.Tests/Workspaces/OpenApiWorkspaceTests.cs

@@ -120,6 +120,38 @@ public void OpenApiWorkspacesCanResolveReferencesToDocumentFragmentsWithJsonPoin
             Assert.Same(responseFragment.Headers["header1"], resolvedElement.Headers["header1"]);
         }
 
+        [Fact]
+        public void OpenApiWorkspacesCanResolveSchemaAnchorAgainstSchemaId()
+        {
+            // Arrange
+            var workspace = new OpenApiWorkspace();
+            var schema = new OpenApiSchema
+            {
+                Id = "https://example.com/schema",
+                Anchor = "address",
+                Type = JsonSchemaType.Object
+            };
+            var document = new OpenApiDocument
+            {
+                BaseUri = new Uri("https://example.com/openapi.yaml"),
+                Components = new OpenApiComponents
+                {
+                    Schemas = new Dictionary<string, IOpenApiSchema>
+                    {
+                        ["person"] = schema
+                    }
+                }
+            };
+
+            workspace.RegisterComponents(document);
+
+            // Act
+            var resolvedSchema = workspace.ResolveReference<OpenApiSchema>("https://example.com/schema#address");
+
+            // Assert
+            Assert.Same(schema, resolvedSchema);
+        }
+
         // Test artifacts
         private static OpenApiDocument CreateCommonDocument()
         {