From fdce6b8c38dba9199f887f659f4ea8146c0bb430 Mon Sep 17 00:00:00 2001
From: James <james@eli.cx>
Date: Fri, 9 Oct 2026 20:02:07 +0100
Subject: [PATCH] feat(rsc): expose closure captures in
 transformHoistInlineDirective meta

---
 .../plugin-rsc/src/transforms/hoist.test.ts   | 29 +++++++++++++++++++
 packages/plugin-rsc/src/transforms/hoist.ts   |  8 ++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/packages/plugin-rsc/src/transforms/hoist.test.ts b/packages/plugin-rsc/src/transforms/hoist.test.ts
index cd91f59ed..501f24933 100644
--- a/packages/plugin-rsc/src/transforms/hoist.test.ts
+++ b/packages/plugin-rsc/src/transforms/hoist.test.ts
@@ -174,6 +174,35 @@ async function cached(value, { offset }, ...rest) {
     ])
   })
 
+  it('exposes closure captures to the runtime', async () => {
+    const input = `
+function Page({ tenant }, label) {
+  async function capturing(query) {
+    "use cache";
+    return [tenant.id, tenant.region, label, query];
+  }
+  async function standalone() {
+    "use cache";
+    return 1;
+  }
+}
+`
+    const ast = await parseAstAsync(input)
+    const bindVars: Record<string, string[]> = {}
+    transformHoistInlineDirective(input, ast, {
+      directive: 'use cache',
+      runtime: (value, name, meta) => {
+        bindVars[name] = meta.bindVars
+        return value
+      },
+    })
+
+    expect(bindVars).toEqual({
+      $$hoist_0_capturing: ['tenant', 'label'],
+      $$hoist_1_standalone: [],
+    })
+  })
+
   it('ignores strings outside a function directive prologue', async () => {
     const input = `
 async function initialized() {
diff --git a/packages/plugin-rsc/src/transforms/hoist.ts b/packages/plugin-rsc/src/transforms/hoist.ts
index c38a3740c..d99413859 100644
--- a/packages/plugin-rsc/src/transforms/hoist.ts
+++ b/packages/plugin-rsc/src/transforms/hoist.ts
@@ -42,6 +42,8 @@ export type TransformHoistInlineDirectiveMeta = {
   directiveMatch: RegExpMatchArray
   /** Original source function before closure captures are added as parameters. */
   valueNode: ArrowFunctionExpression | FunctionDeclaration | FunctionExpression
+  /** Closure captures, in the order they are bound ahead of the original parameters. */
+  bindVars: string[]
 }
 
 export type TransformHoistInlineDirectiveResult = {
@@ -226,7 +228,11 @@ export function transformHoistInlineDirective(
         const runtimeCode = `/* #__PURE__ */ ${runtime(
           implementationName,
           newName,
-          { directiveMatch: match, valueNode: node },
+          {
+            directiveMatch: match,
+            valueNode: node,
+            bindVars: bindVars.map((b) => b.root),
+          },
         )}`
         if (options.hoistRuntime) {
           runtimeHoists.push(