typechecking inputs/outputs in action transform tests (#75935)

This PR attempts to add typechecking to the server actions tests
fixtures in order to add an extra layer of validation against compiler
bugs. (there's a couple!). Unfortunately the tests were pretty
loosey-goosey around undefined variables, so there's a lot of noise in
adding missing imports for `Button` etc. i tried to call out the
interesting changes via PR comments.

Note that this is a bit limited, because we often have to rely on
typescript inferring some sensible types for the outputs -- see e.g. the
issue with `24/output.js` mentioned below. In case typescript can't
infer sensible types for something, we can just exclude that file from
checking. this seems to be pretty rare, so i think it's okay.

We should also definitely add typechecking to the other fixture folders,
but this PR is already big, so i want to do that piecemeal.

### TODO
- [x] invoke the typechecker in CI
- added a `check-compiler-fixtures` script that runs as part of
`types-and-precompiled` (open to feedback, maybe this isn't the right
place?)
- [x] figure out how to make `tsc` error on
`crates/next-custom-transforms/tests/fixture/server-actions/server-graph/51/output.js`,
where we're referencing a non-existent variable `$$RSC_SERVER_ACTION_0`.
right now, it emits no errors
- this is a compiler bug, and i want to catch bugs like this in the
future
  - solution: #75944
- [x] figure out why `tsc` is complaining about a type mismatch in
`crates/next-custom-transforms/tests/fixture/server-actions/server-graph/24/output.js`
- we can work around this by loosening the types for
`registerServerReference`, but i'd rather we didn't have to do that
- this seems to be a bizarre TS behavior where `fn.bind(...)` makes all
the params optional in JS files. ignoring this for now

crates/next-custom-transforms/tests/fixture/server-actions/client-graph/3/input.js

@@ -1,5 +1,7 @@
 'use server'
 
-export const { sampleFunction } = someObject
-export const { sampleFunction2 } = fn()
-export let { 0: sampleFunction3, 1: sampleFunction4 } = [g(), g()]
+import ANYTHING from 'anything'
+
+export const { sampleFunction } = ANYTHING
+export const { sampleFunction2 } = ANYTHING()
+export let { 0: sampleFunction3, 1: sampleFunction4 } = [ANYTHING(), ANYTHING()]

crates/next-custom-transforms/tests/fixture/server-actions/client-graph/5/input.js

@@ -6,6 +6,7 @@ export async function action0(b, c, ...g) {
   return async function action1(d) {
     'use server'
     let f
+    // @ts-expect-error: window is not iterable
     console.log(...window, { window })
     console.log(a, b, action2)
 

crates/next-custom-transforms/tests/fixture/server-actions/index.ts

@@ -0,0 +1,2 @@
+/// <reference types="./next" />
+/// <reference types="./modules" />

crates/next-custom-transforms/tests/fixture/server-actions/modules.d.ts

@@ -0,0 +1,51 @@
+declare module 'database' {
+  export const db: {
+    serialize<T>(cb: () => T): T
+    run(
+      statement: string,
+      args: Record<string, any>,
+      onComplete: (this: { lastID: string }, error?: Error) => void
+    ): void
+  }
+}
+
+declare module 'db' {
+  export default function deleteFromDb(arg: any, ...args: any[]): Promise<void>
+}
+
+declare module 'auth' {
+  export function validator<TFn extends (...args: any[]) => any>(fn: TFn): TFn
+  export function another<TFn extends (...args: any[]) => any>(fn: TFn): TFn
+}
+
+declare module 'anything' {
+  const ANYTHING: any
+  export default ANYTHING
+}
+
+declare module 'foo' {
+  const f: any
+  export default f
+  export const f1: any
+  export const f2: any
+}
+
+declare module 'components' {
+  import React from 'react'
+
+  export function Button(
+    props: {
+      action: () => Promise<any>
+    } & React.ComponentProps<'button'>
+  ): React.ReactNode
+
+  export function Form(
+    props: React.PropsWithChildren<{ action: () => Promise<any> }>
+  ): React.ReactNode
+
+  export function Client(props: Record<string, any>): React.ReactNode
+}
+
+declare module 'navigation' {
+  export function redirect(href: string): void
+}

crates/next-custom-transforms/tests/fixture/server-actions/next.d.ts

@@ -0,0 +1,49 @@
+declare module 'private-next-rsc-action-encryption' {
+  export function encryptActionBoundArgs(
+    actionId: string,
+    ...args: any[]
+  ): Promise<string>
+
+  export function decryptActionBoundArgs(
+    actionId: string,
+    encryptedPromise: Promise<string>
+  ): Promise<any[]>
+}
+
+declare module 'private-next-rsc-server-reference' {
+  export function registerServerReference<T extends (...args: any[]) => any>(
+    reference: T,
+    id: string,
+    exportName: string | null
+  ): T
+}
+
+declare module 'private-next-rsc-action-client-wrapper' {
+  export function callServer(
+    actionId: string,
+    actionArgs: unknown[]
+  ): Promise<unknown>
+
+  export function findSourceMapURL(filename: string): string | null
+
+  const createServerReference: (
+    id: string,
+    callServer: any,
+    encodeFormAction?: any,
+    findSourceMapURL?: any,
+    functionName?: string
+  ) => (...args: unknown[]) => Promise<unknown>
+}
+
+declare module 'private-next-rsc-action-validate' {
+  function ensureServerEntryExports(actions: unknown[]): void
+}
+
+declare module 'private-next-rsc-cache-wrapper' {
+  export function cache<TFn extends (...args: any[]) => Promise<any>>(
+    kind: string,
+    id: string,
+    boundArgsLength: number,
+    fn: TFn
+  ): TFn
+}

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/1/input.js

@@ -1,3 +1,4 @@
+import { Button } from 'components'
 import deleteFromDb from 'db'
 
 export function Item({ id1, id2 }) {

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/1/output.js

@@ -1,5 +1,6 @@
 /* __next_internal_action_entry_do_not_use__ {"406a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0","4090b5db271335765a4b0eab01f044b381b5ebd5cd":"$$RSC_SERVER_ACTION_1"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
+import { Button } from 'components';
 import deleteFromDb from 'db';
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function deleteItem($$ACTION_CLOSURE_BOUND) {
     var [$$ACTION_ARG_0, $$ACTION_ARG_1] = await decryptActionBoundArgs("406a88810ecce4a4e8b59d53b8327d7e98bbf251d7", $$ACTION_CLOSURE_BOUND);

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/16/input.js

@@ -1,3 +1,4 @@
+import { Button } from 'components'
 import deleteFromDb from 'db'
 
 const v1 = 'v1'
@@ -13,7 +14,7 @@ export function Item({ id1, id2 }) {
   return <Button action={deleteItem}>Delete</Button>
 }
 
-const f = (x) => {
+let f = (x) => {
   async function g(y, ...z) {
     'use server'
     return x + y + z[0]
@@ -23,6 +24,14 @@ const f = (x) => {
 const g = (x) => {
   f = async (y, ...z) => {
     'use server'
-    return x + y + z[0]
+    return (
+      x +
+      y +
+      // can't be a `ts-expect-error` because the type of `z` changes to `any` in the output
+      // and it stops being an error
+      //
+      // @ts-ignore: incompatible argument types
+      z[0]
+    )
   }
 }

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/16/output.js

@@ -1,5 +1,6 @@
 /* __next_internal_action_entry_do_not_use__ {"406a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0","7f1c36b06e398c97abe5d5d7ae8c672bfddf4e1b91":"$$RSC_SERVER_ACTION_2","7f90b5db271335765a4b0eab01f044b381b5ebd5cd":"$$RSC_SERVER_ACTION_1"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
+import { Button } from 'components';
 import deleteFromDb from 'db';
 const v1 = 'v1';
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function deleteItem($$ACTION_CLOSURE_BOUND) {
@@ -17,12 +18,16 @@ export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_1 = a
     var [$$ACTION_ARG_0] = await decryptActionBoundArgs("7f90b5db271335765a4b0eab01f044b381b5ebd5cd", $$ACTION_CLOSURE_BOUND);
     return $$ACTION_ARG_0 + y + z[0];
 };
-const f = (x)=>{
+let f = (x)=>{
     var g = registerServerReference($$RSC_SERVER_ACTION_1, "7f90b5db271335765a4b0eab01f044b381b5ebd5cd", null).bind(null, encryptActionBoundArgs("7f90b5db271335765a4b0eab01f044b381b5ebd5cd", x));
 };
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_2 = async function f($$ACTION_CLOSURE_BOUND, y, ...z) {
     var [$$ACTION_ARG_0] = await decryptActionBoundArgs("7f1c36b06e398c97abe5d5d7ae8c672bfddf4e1b91", $$ACTION_CLOSURE_BOUND);
-    return $$ACTION_ARG_0 + y + z[0];
+    return $$ACTION_ARG_0 + y + // can't be a `ts-expect-error` because the type of `z` changes to `any` in the output
+    // and it stops being an error
+    //
+    // @ts-ignore: incompatible argument types
+    z[0];
 };
 const g = (x)=>{
     f = registerServerReference($$RSC_SERVER_ACTION_2, "7f1c36b06e398c97abe5d5d7ae8c672bfddf4e1b91", null).bind(null, encryptActionBoundArgs("7f1c36b06e398c97abe5d5d7ae8c672bfddf4e1b91", x));

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/18/input.js

@@ -1,3 +1,4 @@
+import { Button } from 'components'
 import deleteFromDb from 'db'
 
 const v1 = 'v1'

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/18/output.js

@@ -1,5 +1,6 @@
 /* __next_internal_action_entry_do_not_use__ {"406a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0","4090b5db271335765a4b0eab01f044b381b5ebd5cd":"$$RSC_SERVER_ACTION_1"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
+import { Button } from 'components';
 import deleteFromDb from 'db';
 const v1 = 'v1';
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function action($$ACTION_CLOSURE_BOUND) {

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/19/input.js

@@ -1,3 +1,5 @@
+import { Button } from 'components'
+
 export function Item({ value }) {
   return (
     <>

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/19/output.js

@@ -1,5 +1,6 @@
 /* __next_internal_action_entry_do_not_use__ {"606a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
+import { Button } from 'components';
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function action($$ACTION_CLOSURE_BOUND, value2) {
     var [$$ACTION_ARG_0] = await decryptActionBoundArgs("606a88810ecce4a4e8b59d53b8327d7e98bbf251d7", $$ACTION_CLOSURE_BOUND);
     return $$ACTION_ARG_0 * value2;

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/2/input.js

@@ -1,3 +1,6 @@
+import { validator } from 'auth'
+import { Button } from 'components'
+
 async function myAction(a, b, c) {
   'use server'
   console.log('a')
@@ -8,6 +11,6 @@ export default function Page() {
 }
 
 // TODO: should use `action` as function name?
-export const action = withValidate(async () => {
+export const action = validator(async () => {
   'use server'
 })

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/2/output.js

@@ -1,6 +1,8 @@
-/*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ /* __next_internal_action_entry_do_not_use__ {"0090b5db271335765a4b0eab01f044b381b5ebd5cd":"$$RSC_SERVER_ACTION_1","706a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0"} */ import { registerServerReference } from "private-next-rsc-server-reference";
+/* __next_internal_action_entry_do_not_use__ {"0090b5db271335765a4b0eab01f044b381b5ebd5cd":"$$RSC_SERVER_ACTION_1","706a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
-export const $$RSC_SERVER_ACTION_0 = async function myAction(a, b, c) {
+import { validator } from 'auth';
+import { Button } from 'components';
+export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function myAction(a, b, c) {
     console.log('a');
 };
 var myAction = registerServerReference($$RSC_SERVER_ACTION_0, "706a88810ecce4a4e8b59d53b8327d7e98bbf251d7", null);
@@ -9,4 +11,4 @@ export default function Page() {
 }
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_1 = async function() {};
 // TODO: should use `action` as function name?
-export const action = withValidate(registerServerReference($$RSC_SERVER_ACTION_1, "0090b5db271335765a4b0eab01f044b381b5ebd5cd", null));
+export const action = validator(registerServerReference($$RSC_SERVER_ACTION_1, "0090b5db271335765a4b0eab01f044b381b5ebd5cd", null));

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/20/input.js

@@ -1,4 +1,5 @@
 'use server'
 
+/** @type {[any]} */
 const [foo] = [null]
 export default foo

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/20/output.js

@@ -1,6 +1,6 @@
 /* __next_internal_action_entry_do_not_use__ {"7fc18c215a6b7cdc64bf709f3a714ffdef1bf9651d":"default"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
-const [foo] = [
+/** @type {[any]} */ const [foo] = [
     null
 ];
 export default /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ foo;

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/21/input.js

@@ -1,11 +1,12 @@
 import { validator, another } from 'auth'
+import { Button } from 'components'
 
 const x = 1
 
 export default function Page() {
   const y = 1
   return (
-    <Foo
+    <Button
       // TODO: should use `action` as function name?
       action={validator(async function (z) {
         'use server'

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/21/output.js

@@ -1,14 +1,15 @@
 /* __next_internal_action_entry_do_not_use__ {"001c36b06e398c97abe5d5d7ae8c672bfddf4e1b91":"$$RSC_SERVER_ACTION_2","0090b5db271335765a4b0eab01f044b381b5ebd5cd":"$$RSC_SERVER_ACTION_1","606a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
 import { validator, another } from 'auth';
+import { Button } from 'components';
 const x = 1;
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function($$ACTION_CLOSURE_BOUND, z) {
     var [$$ACTION_ARG_0] = await decryptActionBoundArgs("606a88810ecce4a4e8b59d53b8327d7e98bbf251d7", $$ACTION_CLOSURE_BOUND);
     return x + $$ACTION_ARG_0 + z;
 };
 export default function Page() {
     const y = 1;
-    return <Foo // TODO: should use `action` as function name?
+    return <Button // TODO: should use `action` as function name?
     action={validator(registerServerReference($$RSC_SERVER_ACTION_0, "606a88810ecce4a4e8b59d53b8327d7e98bbf251d7", null).bind(null, encryptActionBoundArgs("606a88810ecce4a4e8b59d53b8327d7e98bbf251d7", y)))}/>;
 }
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_1 = async function() {};

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/25/input.js

@@ -1,3 +1,4 @@
+import { Button } from 'components'
 import deleteFromDb from 'db'
 
 export function Item({ id1, id2 }) {
@@ -26,6 +27,8 @@ export function Item2({ id1, id2 }) {
 
   return temp
 
+  // FIXME: invalid transformation of hoisted functions (https://github.com/vercel/next.js/issues/57392)
+  // (remove output.js from `tsconfig.json#exclude` to see the error)
   async function deleteItem() {
     'use server'
     await deleteFromDb(id1)

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/25/output.js

@@ -1,5 +1,6 @@
 /* __next_internal_action_entry_do_not_use__ {"406a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0","4090b5db271335765a4b0eab01f044b381b5ebd5cd":"$$RSC_SERVER_ACTION_1"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
+import { Button } from 'components';
 import deleteFromDb from 'db';
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function deleteItem($$ACTION_CLOSURE_BOUND) {
     var [$$ACTION_ARG_0, $$ACTION_ARG_1] = await decryptActionBoundArgs("406a88810ecce4a4e8b59d53b8327d7e98bbf251d7", $$ACTION_CLOSURE_BOUND);
@@ -14,7 +15,9 @@ export function Item({ id1, id2 }) {
     })();
     var deleteItem = registerServerReference($$RSC_SERVER_ACTION_0, "406a88810ecce4a4e8b59d53b8327d7e98bbf251d7", null).bind(null, encryptActionBoundArgs("406a88810ecce4a4e8b59d53b8327d7e98bbf251d7", id1, id2));
 }
-export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_1 = async function deleteItem($$ACTION_CLOSURE_BOUND) {
+export const // FIXME: invalid transformation of hoisted functions (https://github.com/vercel/next.js/issues/57392)
+// (remove output.js from `tsconfig.json#exclude` to see the error)
+/*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_1 = async function deleteItem($$ACTION_CLOSURE_BOUND) {
     var [$$ACTION_ARG_0, $$ACTION_ARG_1] = await decryptActionBoundArgs("4090b5db271335765a4b0eab01f044b381b5ebd5cd", $$ACTION_CLOSURE_BOUND);
     await deleteFromDb($$ACTION_ARG_0);
     await deleteFromDb($$ACTION_ARG_1);

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/28/input.js

@@ -4,9 +4,12 @@ function Comp(b, c, ...g) {
   return async function action1(d) {
     'use server'
     let f
+    // @ts-expect-error: window is not iterable
     console.log(...window, { window })
     console.log(a, b, action2)
 
+    // FIXME: invalid transformation of hoisted functions (https://github.com/vercel/next.js/issues/57392)
+    // (remove output.js from `tsconfig.json#exclude` to see the error)
     async function action2(e) {
       'use server'
       console.log(a, c, d, e, f, g)

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/28/output.js

@@ -1,7 +1,9 @@
 /* __next_internal_action_entry_do_not_use__ {"601c36b06e398c97abe5d5d7ae8c672bfddf4e1b91":"$$RSC_SERVER_ACTION_2","606a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0","6090b5db271335765a4b0eab01f044b381b5ebd5cd":"$$RSC_SERVER_ACTION_1"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
 let a, f;
-export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function action2($$ACTION_CLOSURE_BOUND, e) {
+export const // FIXME: invalid transformation of hoisted functions (https://github.com/vercel/next.js/issues/57392)
+// (remove output.js from `tsconfig.json#exclude` to see the error)
+/*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function action2($$ACTION_CLOSURE_BOUND, e) {
     var [$$ACTION_ARG_0, $$ACTION_ARG_1, $$ACTION_ARG_2, $$ACTION_ARG_3] = await decryptActionBoundArgs("606a88810ecce4a4e8b59d53b8327d7e98bbf251d7", $$ACTION_CLOSURE_BOUND);
     console.log(a, $$ACTION_ARG_0, $$ACTION_ARG_1, e, $$ACTION_ARG_2, $$ACTION_ARG_3);
 };
@@ -13,6 +15,7 @@ export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_1 = a
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_2 = async function action1($$ACTION_CLOSURE_BOUND, d) {
     var [$$ACTION_ARG_0, $$ACTION_ARG_1, $$ACTION_ARG_2] = await decryptActionBoundArgs("601c36b06e398c97abe5d5d7ae8c672bfddf4e1b91", $$ACTION_CLOSURE_BOUND);
     let f;
+    // @ts-expect-error: window is not iterable
     console.log(...window, {
         window
     });

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/30/input.js

@@ -6,9 +6,12 @@ export async function action0(b, c, ...g) {
   return async function action1(d) {
     'use server'
     let f
+    // @ts-expect-error: window is not iterable
     console.log(...window, { window })
     console.log(a, b, action2)
 
+    // FIXME: invalid transformation of hoisted functions (https://github.com/vercel/next.js/issues/57392)
+    // (remove output.js from `tsconfig.json#exclude` to see the error)
     async function action2(e) {
       'use server'
       console.log(a, c, d, e, f, g)

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/30/output.js

@@ -1,7 +1,9 @@
 /* __next_internal_action_entry_do_not_use__ {"601c36b06e398c97abe5d5d7ae8c672bfddf4e1b91":"$$RSC_SERVER_ACTION_2","606a88810ecce4a4e8b59d53b8327d7e98bbf251d7":"$$RSC_SERVER_ACTION_0","6090b5db271335765a4b0eab01f044b381b5ebd5cd":"$$RSC_SERVER_ACTION_1","7f0090eaf4e1f08a2d94f6be401e54a2ded399b87c":"action0"} */ import { registerServerReference } from "private-next-rsc-server-reference";
 import { encryptActionBoundArgs, decryptActionBoundArgs } from "private-next-rsc-action-encryption";
 let a, f;
-export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function action2($$ACTION_CLOSURE_BOUND, e) {
+export const // FIXME: invalid transformation of hoisted functions (https://github.com/vercel/next.js/issues/57392)
+// (remove output.js from `tsconfig.json#exclude` to see the error)
+/*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_0 = async function action2($$ACTION_CLOSURE_BOUND, e) {
     var [$$ACTION_ARG_0, $$ACTION_ARG_1, $$ACTION_ARG_2, $$ACTION_ARG_3] = await decryptActionBoundArgs("606a88810ecce4a4e8b59d53b8327d7e98bbf251d7", $$ACTION_CLOSURE_BOUND);
     console.log(a, $$ACTION_ARG_0, $$ACTION_ARG_1, e, $$ACTION_ARG_2, $$ACTION_ARG_3);
 };
@@ -13,6 +15,7 @@ export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_1 = a
 export const /*#__TURBOPACK_DISABLE_EXPORT_MERGING__*/ $$RSC_SERVER_ACTION_2 = async function action1($$ACTION_CLOSURE_BOUND, d) {
     var [$$ACTION_ARG_0, $$ACTION_ARG_1, $$ACTION_ARG_2] = await decryptActionBoundArgs("601c36b06e398c97abe5d5d7ae8c672bfddf4e1b91", $$ACTION_CLOSURE_BOUND);
     let f;
+    // @ts-expect-error: window is not iterable
     console.log(...window, {
         window
     });

crates/next-custom-transforms/tests/fixture/server-actions/server-graph/39/input.js

@@ -10,5 +10,6 @@ async function Component({ foo }) {
   }
 
   const data = await fn()
+  // @ts-expect-error: data is not a valid react child
   return <div>{data}</div>
 }