This PR fixes a slight performance regression introduced in #85519 where
inline async function expressions were created for each unique set of
arguments passed to a `'use cache'` function.
For a function like this:
```js
export async function getCachedData(id) {
'use cache';
return fetch(`/api/data/${id}`);
}
```
we were previously generating (simplified):
```js
export var $$RSC_SERVER_CACHE_0 = cache("default", "0815", 0, async function(id) {
return fetch(`/api/data/${id}`);
});
```
In #85519, we restructured this to ensure proper stack frames in error
messages (simplified):
```js
export var $$RSC_SERVER_CACHE_0 = React.cache(function getCachedData() {
return cache("default", "0815", 0, async function(id) {
return fetch(`/api/data/${id}`);
}, arguments);
});
```
However, this introduced a small performance issue: the inner async
function expression was passed inline to the cache wrapper. While
`React.cache` memoizes the outer function, each unique set of arguments
would cause a new inner function object to be allocated.
Now we're generating (simplified):
```js
const $$RSC_SERVER_CACHE_0_INNER = async function getCachedData(id) {
return fetch(`/api/data/${id}`);
};
export var $$RSC_SERVER_CACHE_0 = React.cache(function getCachedData() {
return cache("default", "0815", 0, $$RSC_SERVER_CACHE_0_INNER, arguments);
});
```
The cache implementation is now hoisted to module scope with an `_INNER`
suffix as a const declaration with a named function expression. The
function name is preserved to ensure proper stack traces in dev. This
eliminates the repeated function allocations while preserving the
improvements from #85519.
Hendrik Liebau