feat: configure kv binding name with env var (#83)

.changeset/yellow-cougars-explain.md

@@ -0,0 +1,7 @@
+---
+"@opennextjs/cloudflare": minor
+---
+
+feat: configure kv binding name with env var
+
+The Workers KV binding used in the Next.js cache handler can be given a custom name with the `__OPENNEXT_KV_BINDING_NAME` environment variable at build-time, instead of defaulting to `NEXT_CACHE_WORKERS_KV`.

packages/cloudflare/src/cli/build/patches/investigated/patch-cache.ts

@@ -3,7 +3,15 @@ import { build } from "esbuild";
 import { join } from "node:path";
 
 /**
- * Install the cloudflare KV cache handler
+ * Sets up the OpenNext cache handler in a Next.js build.
+ *
+ * The cache handler used by Next.js is normally defined in the config file as a path. At runtime,
+ * Next.js would then do a dynamic require on a transformed version of the path to retrieve the
+ * cache handler and create a new instance of it.
+ *
+ * This is problematic in workerd due to the dynamic import of the file that is not known from
+ * build-time. Therefore, we have to manually override the default way that the cache handler is
+ * instantiated with a dynamic require that uses a string literal for the path.
  */
 export async function patchCache(code: string, config: Config): Promise<string> {
   console.log("# patchCache");

packages/cloudflare/src/cli/config.ts

@@ -3,13 +3,6 @@ import { readdirSync, statSync } from "node:fs";
 
 const PACKAGE_NAME = "@opennextjs/cloudflare";
 
-// Make this user configurable
-const UserConfig = {
-  cache: {
-    bindingName: "NEXT_CACHE_WORKERS_KV",
-  },
-};
-
 export type Config = {
   // Timestamp for when the build was started
   buildTimestamp: number;
@@ -63,6 +56,8 @@ export function getConfig(appDir: string, outputDir: string): Config {
   const internalPackage = path.join(nodeModules, ...PACKAGE_NAME.split("/"));
   const internalTemplates = path.join(internalPackage, "cli", "templates");
 
+  process.env.__OPENNEXT_KV_BINDING_NAME ??= "NEXT_CACHE_WORKERS_KV";
+
   return {
     buildTimestamp: Date.now(),
 
@@ -79,7 +74,7 @@ export function getConfig(appDir: string, outputDir: string): Config {
     },
 
     cache: {
-      kvBindingName: UserConfig.cache.bindingName,
+      kvBindingName: process.env.__OPENNEXT_KV_BINDING_NAME,
     },
 
     internalPackageName: PACKAGE_NAME,