refactor(config): skip cycle tracking for leaf configs

Author: chenjiahan

packages/rstack/src/configLayers.ts

@@ -38,19 +38,21 @@ export const flattenConfigLayers = (
   const ancestors = new Map<RstackConfig, string>();
 
   const visit = (config: RstackConfig, path: string): void => {
-    const ancestorPath = ancestors.get(config);
-    if (ancestorPath !== undefined) {
-      throw new Error(
-        `Circular config inheritance at ${path}: references ${ancestorPath}.`,
-      );
-    }
+    if (config.extends?.length) {
+      const ancestorPath = ancestors.get(config);
+      if (ancestorPath !== undefined) {
+        throw new Error(
+          `Circular config inheritance at ${path}: references ${ancestorPath}.`,
+        );
+      }
 
-    ancestors.set(config, path);
-    config.extends?.forEach((inherited, index) => {
-      visit(inherited, `${path}.extends[${index}]`);
-    });
+      ancestors.set(config, path);
+      config.extends.forEach((inherited, index) => {
+        visit(inherited, `${path}.extends[${index}]`);
+      });
+      ancestors.delete(config);
+    }
     layers.push(normalizeRstackConfig(config));
-    ancestors.delete(config);
   };
 
   configs.forEach((config, index) => visit(config, `extends[${index}]`));

packages/rstack/tests/config/flatten.test.ts

@@ -19,10 +19,14 @@ test('flattens nested configs in order and preserves repeated references without
     base,
   ]);
   expect(app).not.toHaveBeenCalled();
-  expect(left.extends).toEqual([base]);
-  expect(nested.extends).toEqual([left]);
-  expect(right.extends).toEqual([base]);
-  expect(configs).toEqual([nested, right, base]);
+  expect(configs).toEqual([
+    {
+      extends: [{ extends: [base], fmt: { singleQuote: true } }],
+      fmt: { semi: false },
+    },
+    { extends: [base], fmt: { tabWidth: 4 } },
+    base,
+  ]);
 });
 
 test('reports the inheritance positions of a direct cycle', () => {