fix: count paren-less arrow actions in the one-action check rule (#488)

The arrow-export regex required a '(' after '=', so a paren-less single-param
arrow (export const x = id => ...) was not counted and a two-action file
slipped past. Broaden to match paren-less arrows and function expressions
(anchored on => / function so a plain value const still does not count).

Author: t

packages/server/src/check.js

@@ -746,7 +746,10 @@ export async function checkConventions(appDir) {
       let m;
       const reFn = /\bexport\s+(?:async\s+)?function\s*\*?\s+([A-Za-z_$][\w$]*)/g;
       while ((m = reFn.exec(scan))) names.add(m[1]);
-      const reArrow = /\bexport\s+const\s+([A-Za-z_$][\w$]*)\s*=\s*(?:async\s*)?\(/g;
+      // An arrow-const action: `export const x = (...) => ...`, the paren-less
+      // `export const x = id => ...`, or a function expression. The `=>` /
+      // `function` anchor keeps a plain `export const N = 5` from counting.
+      const reArrow = /\bexport\s+const\s+([A-Za-z_$][\w$]*)\s*=\s*(?:async\s+)?(?:function\b|(?:\([^)]*\)|[A-Za-z_$][\w$]*)\s*=>)/g;
       while ((m = reArrow.exec(scan))) names.add(m[1]);
       if (/\bexport\s+default\b/.test(scan)) names.add('default');
       const actions = [...names].filter((n) => !RESERVED_CONFIG.has(n));

packages/server/test/action-verbs/check-one-action.test.js

@@ -42,3 +42,15 @@ test('counts an arrow-const action too', async () => {
   assert.ok(has(await checkConventions(dir)), 'arrow + fn => two actions');
   rmSync(dir, { recursive: true, force: true });
 });
+
+test('counts a paren-less single-param arrow action', async () => {
+  const dir = app({ 'a.server.ts': `'use server';\nexport const method='GET';\nexport const getA = id => id;\nexport async function getB(){return 1}\n` });
+  assert.ok(has(await checkConventions(dir)), 'paren-less arrow + fn => two actions');
+  rmSync(dir, { recursive: true, force: true });
+});
+
+test('a plain non-function const export is not counted as an action', async () => {
+  const dir = app({ 'a.server.ts': `'use server';\nexport const method='GET';\nexport const MAX = 5;\nexport async function getA(id){return id+MAX}\n` });
+  assert.equal(has(await checkConventions(dir)), false, 'a value const is not an action');
+  rmSync(dir, { recursive: true, force: true });
+});