refactor(config): merge staged config layers

packages/rstack/src/configLayers.ts

@@ -63,3 +63,19 @@ export const resolveRslintConfig = async (
   const configs = await resolveConfigLayers(layers, 'lint');
   return configs.length > 1 ? configs.flat() : configs[0];
 };
+
+export const resolveStagedConfig = async (
+  layers: readonly Configs[],
+): Promise<StagedConfig | undefined> => {
+  const configs = await resolveConfigLayers(layers, 'staged');
+  if (configs.length <= 1) {
+    return configs[0];
+  }
+
+  // Top-level task generators replace the whole config rather than glob keys.
+  return configs.reduce((merged, config) =>
+    typeof merged === 'function' || typeof config === 'function'
+      ? config
+      : { ...merged, ...config },
+  );
+};

packages/rstack/src/staged.ts

@@ -2,6 +2,7 @@ import lintStaged from 'lint-staged';
 import { parseArgs } from './cli/args.ts';
 import { printCommandHelp } from './cli/help.ts';
 import { loadRstackConfig } from './config.ts';
+import { resolveStagedConfig } from './configLayers.ts';
 
 export type StagedSyncTaskGenerator = (
   stagedFileNames: readonly string[],
@@ -51,8 +52,8 @@ export async function runStagedCLI(args: string[]): Promise<void> {
   }
 
   const { configs } = await loadRstackConfig();
-  const stagedConfig = configs.staged;
-  if (!stagedConfig) {
+  const stagedConfig = await resolveStagedConfig([configs]);
+  if (stagedConfig === undefined) {
     throw new Error(
       'No define.staged config found. Add define.staged({ "*": "your-command" }) to rstack config file',
     );

packages/rstack/tests/config/staged-merge.test.ts

@@ -0,0 +1,50 @@
+import { expect, rs, test } from 'rstack/test';
+import { resolveStagedConfig } from '../../src/configLayers.ts';
+
+test('shallowly merges staged globs and replaces task arrays', async () => {
+  const generate = rs.fn(() => 'rs fmt');
+  const task = rs.fn();
+  const config = await resolveStagedConfig([
+    {
+      staged: {
+        '*.ts': ['rs lint', 'rs fmt'],
+        '*.md': generate,
+        '*.json': { title: 'Check JSON', task },
+      },
+    },
+    { staged: { '*.ts': ['rs check'], '*.css': 'rs fmt' } },
+  ]);
+
+  expect(config).toEqual({
+    '*.ts': ['rs check'],
+    '*.md': generate,
+    '*.json': { title: 'Check JSON', task },
+    '*.css': 'rs fmt',
+  });
+  expect(generate).not.toHaveBeenCalled();
+  expect(task).not.toHaveBeenCalled();
+});
+
+test('a top-level task generator replaces earlier staged config without running', async () => {
+  const generate = rs.fn(() => ['rs check']);
+  const config = await resolveStagedConfig([
+    { staged: { '*.ts': 'rs lint' } },
+    { staged: generate },
+  ]);
+
+  expect(config).toBe(generate);
+  expect(generate).not.toHaveBeenCalled();
+});
+
+test('glob maps after a top-level task generator start a new staged config', async () => {
+  const generate = rs.fn(() => ['rs check']);
+  const config = await resolveStagedConfig([
+    { staged: { '*.ts': 'rs lint' } },
+    { staged: generate },
+    { staged: { '*.md': 'rs fmt' } },
+    { staged: { '*.css': 'rs fmt' } },
+  ]);
+
+  expect(config).toEqual({ '*.md': 'rs fmt', '*.css': 'rs fmt' });
+  expect(generate).not.toHaveBeenCalled();
+});