Update no-exports-from-components rule to allow exceptions (#395)

* Update no-exports-from-components rule to allow exceptions

* Create many-carrots-doubt.md

* fix

.changeset/many-carrots-doubt.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-astro": patch
+---
+
+Update `astro/no-exports-from-components` rule to allow exceptions

docs/rules/no-exports-from-components.md

@@ -13,6 +13,10 @@ since: "v1.1.0"
 This rule reports value exports from Astro components.
 The use of typed exports are still allowed.
 
+However, there are exceptions for specific named exports that are allowed:
+- `getStaticPath`: This function can be exported for dynamic routing purposes.
+- `prerender`: This constant can be exported to opt-in to pre-rendering in server mode.
+
 <ESLintCodeBlock>
 
 <!--eslint-skip-->
@@ -22,6 +26,10 @@ The use of typed exports are still allowed.
 /* eslint astro/no-exports-from-components: "error" */
 /* ✓ GOOD */
 export type A = number | boolean
+export const getStaticPath = () => {
+  // logic here
+}
+export const prerender = true;
 /* ✗ BAD */
 export const x = 42
 ---

src/rules/no-exports-from-components.ts

@@ -2,6 +2,8 @@ import type { TSESTree } from "@typescript-eslint/types"
 import { createRule } from "../utils"
 import { getSourceCode } from "../utils/compat"
 
+const ALLOWED_EXPORTS = new Set(["getStaticPath", "prerender"])
+
 export default createRule("no-exports-from-components", {
   meta: {
     docs: {
@@ -34,6 +36,20 @@ export default createRule("no-exports-from-components", {
       if (node.type.startsWith("TS") && !node.type.endsWith("Expression")) {
         return
       }
+      if (
+        (node.type === "FunctionDeclaration" &&
+          node.id &&
+          ALLOWED_EXPORTS.has(node.id.name)) ||
+        (node.type === "VariableDeclaration" &&
+          node.declarations.every(
+            (decl) =>
+              decl.id.type === "Identifier" &&
+              ALLOWED_EXPORTS.has(decl.id.name),
+          ))
+      ) {
+        // Allow specific named exports
+        return
+      }
       context.report({
         node,
         messageId: "disallowExport",
@@ -56,7 +72,11 @@ export default createRule("no-exports-from-components", {
         if (node.exportKind === "type") return
         verifyDeclaration(node.declaration)
         for (const spec of node.specifiers) {
-          if (spec.exportKind === "type") return
+          if (spec.exportKind === "type") continue
+          if (ALLOWED_EXPORTS.has(spec.exported.name)) {
+            // Allow specific named exports
+            continue
+          }
           context.report({
             node: spec,
             messageId: "disallowExport",

tests/fixtures/rules/no-exports-from-components/valid/exceptions-01-input.astro

@@ -0,0 +1,11 @@
+---
+// This file is used to test the exceptions for the `no-exports-from-components` rule.
+// The following exports are allowed as exceptions.
+export const getStaticPath = (): { param: unknown }[] => {
+  // logic here
+  return [{ param: "value" }]
+}
+export const prerender = true
+---
+
+<div>Hello World</div>

tests/fixtures/rules/no-exports-from-components/valid/exceptions-02-input.astro

@@ -0,0 +1,9 @@
+---
+// This file is used to test the exception for the `getStaticPath` function in the `no-exports-from-components` rule.
+export async function getStaticPath(): Promise<{ param: unknown }[]> {
+  // logic here
+  return []
+}
+---
+
+<div>Hello World</div>

tests/fixtures/rules/no-exports-from-components/valid/exceptions-03-input.astro

@@ -0,0 +1,13 @@
+---
+// This file is used to test the exceptions for the `no-exports-from-components` rule.
+// The following exports are allowed as exceptions.
+const getStaticPath = (): { param: unknown }[] => {
+  // logic here
+  return []
+}
+const prerender = true
+
+export { getStaticPath, prerender }
+---
+
+<div>Hello World</div>