## Background
Currently route handlers will be attempted to statically generate the
same as normal pages in app router. If a route handler accessed dynamic
data such as `cookies()`, `headers()`, `req.url`, or similar we would
bail from this static generation but this didn't handle the case where
you would do data fetching via a non-fetch based library e.g. `redis` or
even using `Date.now()` or `Math.random()` so users would expect these
to be run every request like normal API endpoints but they would be
static so wouldn't be executed again after a build.
## New Behavior
As discussed this disable the default static generation handling for
route handlers as we've seen this confuse our users since in most cases
when creating a route handler you are handling dynamic workloads. This
doesn't remove the ability to static generate route handlers though as
you can still manually specify:
If you specify `export const revalidate = 1` we will still bail if
dynamic data is accessed to prevent accidental `revalidate` configuring
but this can be avoided via `force-static` being used as well.
```js
export const dynamic = 'force-static'
// or
export const dynamic = 'error'
// or
export const revalidate = false
// or
export const revalidate = 1 // value great than 0
// or
export const generateStaticParams() {}
```
---------
Co-authored-by: Zack Tanner <1939140+ztanner@users.noreply.github.com>
### What?
In the previous PR (#60249), it was found that the case when the
response size is larger than 2MB is not sufficiently covered by tests
[[comment](https://github.com/vercel/next.js/pull/60249#pullrequestreview-1807140518)]
### How?
I added a few more checks.
Just checking the number of API calls is not enough - I believe it is
important to additionally verify what exactly the page received.
If I'm honest, I couldn't find the exact reason why data is loaded after
application start when using `customCacheHandler`, but without it -
during build. It seems like something in the butcher. Therefore, in this
part, I simply configured it for the current version.
---------
Co-authored-by: JJ Kasper <jj@jjsweb.site>
### Fixing a bug
### What?
Disable 2MB limit for custom incrementalCacheHandler
### Why?
The limit is necessary because `FetchCache` has a 2MB limit, but it
seems there was a miscommunication regarding the key coincidence, where
`fetchCache` is a flag indicating that the method is called from fetch,
rather than indicating that the `FetchCache` Provider is currently being
used.
We do not use Vercel, and as I understand it, we do not have the
opportunity to use this functionality.
In any case, it is more important for us to increase the limits, and in
some cases, using a file storage is even preferable.
### How?
I have created a flag that determines whether the use of `FetchCache` is
possible at least in theory - if no custom provider is passed, and
additionally configured it so that it is not an implementation of
`FetchCache` as a protection against special individuals (*like me :)*).
If everything is fine, I will write proper tests.
Also, I would like to recommend making `FileSystemCache` public (_i.e.
support it as public functionality_) so that it can be imported and
extended or simply used to fix only it.
Fixes#48324 (partially)
---------
Co-authored-by: JJ Kasper <jj@jjsweb.site>
JJ Kasper