feat: separate build data into files (#1181)

Previously, it was a single JSON object. Separating it into multiple
files theoretically enables lazy loading.

packages/waku/src/lib/builder/build.ts

@@ -7,7 +7,11 @@ import type { LoggingFunction, RollupLog } from 'rollup';
 import type { ReactNode } from 'react';
 
 import type { Config } from '../../config.js';
-import { setAllEnvInternal, unstable_getPlatformObject } from '../../server.js';
+import {
+  setAllEnvInternal,
+  iterateAllPlatformDataInternal,
+  unstable_getPlatformObject,
+} from '../../server.js';
 import type { EntriesPrd } from '../types.js';
 import type { ResolvedConfig } from '../config.js';
 import { resolveConfig } from '../config.js';
@@ -763,9 +767,36 @@ export async function build(options: {
   delete platformObject.buildOptions.unstable_phase;
 
   if (existsSync(distEntriesFile)) {
+    const DIST_PLATFORM_DATA = 'platform-data';
+    const keys = new Set<string>();
+    await mkdir(joinPath(rootDir, config.distDir, DIST_PLATFORM_DATA), {
+      recursive: true,
+    });
+    for (const [key, data] of iterateAllPlatformDataInternal()) {
+      keys.add(key);
+      const destFile = joinPath(
+        rootDir,
+        config.distDir,
+        DIST_PLATFORM_DATA,
+        key + '.js',
+      );
+      await writeFile(destFile, `export default ${JSON.stringify(data)};`);
+    }
     await appendFile(
       distEntriesFile,
-      `export const buildData = ${JSON.stringify(platformObject.buildData)};`,
+      `
+export function loadPlatformData(key) {
+  switch (key) {
+    ${Array.from(keys)
+      .map(
+        (k) =>
+          `case '${k}': return import('./${DIST_PLATFORM_DATA}/${k}.js').then((m) => m.default);`,
+      )
+      .join('\n')}
+    default: throw new Error('Cannot find platform data: ' + key);
+  }
+}
+`,
     );
   }
 }

packages/waku/src/lib/middleware/handler.ts

@@ -2,7 +2,10 @@ import type { ReactNode } from 'react';
 
 import { resolveConfig, extractPureConfig } from '../config.js';
 import type { PureConfig } from '../config.js';
-import { setAllEnvInternal, unstable_getPlatformObject } from '../../server.js';
+import {
+  setAllEnvInternal,
+  setPlatformDataLoaderInternal,
+} from '../../server.js';
 import type { HandleRequest, HandlerRes } from '../types.js';
 import type { Middleware, HandlerContext } from './types.js';
 import { renderRsc, decodeBody, decodePostAction } from '../renderers/rsc.js';
@@ -76,8 +79,8 @@ export const handler: Middleware = (options) => {
   const configPromise =
     options.cmd === 'start'
       ? entriesPromise.then(async (entries) => {
-          if (entries.buildData) {
-            unstable_getPlatformObject().buildData = entries.buildData;
+          if (entries.loadPlatformData) {
+            setPlatformDataLoaderInternal(entries.loadPlatformData);
           }
           return resolveConfig(await entries.loadConfig());
         })

packages/waku/src/lib/plugins/vite-plugin-deploy-cloudflare.ts

@@ -13,7 +13,10 @@ import { randomBytes } from 'node:crypto';
 
 import type { Plugin } from 'vite';
 
-import { unstable_getPlatformObject } from '../../server.js';
+import {
+  iterateAllPlatformDataInternal,
+  unstable_getPlatformObject,
+} from '../../server.js';
 import { SRC_ENTRIES } from '../constants.js';
 import { DIST_ENTRIES_JS, DIST_PUBLIC } from '../builder/constants.js';
 
@@ -207,9 +210,34 @@ export function deployCloudflarePlugin(opts: {
         functionDir: workerDistDir,
       });
 
+      const DIST_PLATFORM_DATA = 'platform-data';
+      const keys = new Set<string>();
+      mkdirSync(path.join(workerDistDir, DIST_PLATFORM_DATA), {
+        recursive: true,
+      });
+      for (const [key, data] of iterateAllPlatformDataInternal()) {
+        keys.add(key);
+        const destFile = path.join(
+          workerDistDir,
+          DIST_PLATFORM_DATA,
+          key + '.js',
+        );
+        writeFileSync(destFile, `export default ${JSON.stringify(data)};`);
+      }
       appendFileSync(
         path.join(workerDistDir, DIST_ENTRIES_JS),
-        `export const buildData = ${JSON.stringify(platformObject.buildData)};`,
+        `
+export function loadPlatformData(key) {
+  switch (key) {
+    ${Array.from(keys)
+      .map(
+        (k) => `case '${k}': return import('./${DIST_PLATFORM_DATA}/${k}.js');`,
+      )
+      .join('\n')}
+    default: throw new Error('Cannot find platform data: ' + key);
+  }
+}
+`,
       );
 
       const wranglerTomlFile = path.join(rootDir, 'wrangler.toml');

packages/waku/src/lib/types.ts

@@ -85,7 +85,7 @@ export type EntriesPrd = EntriesDev & {
   loadModule: (id: string) => Promise<unknown>;
   dynamicHtmlPaths: [pathSpec: PathSpec, htmlHead: string][];
   publicIndexHtml: string;
-  buildData?: Record<string, unknown>; // must be JSON serializable
+  loadPlatformData?: (key: string) => Promise<unknown>;
 };
 
 export type HandlerReq = {

packages/waku/src/router/define-router.ts

@@ -2,7 +2,8 @@ import { createElement } from 'react';
 import type { ReactNode } from 'react';
 
 import {
-  unstable_getPlatformObject,
+  unstable_getPlatformData,
+  unstable_setPlatformData,
   unstable_createAsyncIterable as createAsyncIterable,
 } from '../server.js';
 import { unstable_defineEntries as defineEntries } from '../minimal/server.js';
@@ -112,7 +113,6 @@ export function unstable_defineRouter(fns: {
     status?: number;
   }>;
 }) {
-  const platformObject = unstable_getPlatformObject();
   type MyPathConfig = {
     pathSpec: PathSpec;
     pathname: string | undefined;
@@ -127,7 +127,9 @@ export function unstable_defineRouter(fns: {
   }[];
   let cachedPathConfig: MyPathConfig | undefined;
   const getMyPathConfig = async (): Promise<MyPathConfig> => {
-    const pathConfig = platformObject.buildData?.defineRouterPathConfigs;
+    const pathConfig = await unstable_getPlatformData(
+      'defineRouterPathConfigs',
+    );
     if (pathConfig) {
       return pathConfig as MyPathConfig;
     }
@@ -432,8 +434,7 @@ globalThis.__WAKU_ROUTER_PREFETCH__ = (path) => {
         });
       }
 
-      platformObject.buildData ||= {};
-      platformObject.buildData.defineRouterPathConfigs = pathConfig;
+      await unstable_setPlatformData('defineRouterPathConfigs', pathConfig);
       return tasks;
     });
 

packages/waku/src/router/fs-router.ts

@@ -1,4 +1,8 @@
-import { unstable_getPlatformObject } from '../server.js';
+import {
+  unstable_getPlatformData,
+  unstable_setPlatformData,
+  unstable_getPlatformObject,
+} from '../server.js';
 import { createPages, METHODS } from './create-pages.js';
 import type { Method } from './create-pages.js';
 
@@ -14,8 +18,7 @@ export function fsRouter(
   const platformObject = unstable_getPlatformObject();
   return createPages(
     async ({ createPage, createLayout, createRoot, createApi }) => {
-      let files: string[] | undefined = platformObject.buildData
-        ?.fsRouterFiles as string[] | undefined;
+      let files = await unstable_getPlatformData<string[]>('fsRouterFiles');
       if (!files) {
         // dev and build only
         const [
@@ -56,8 +59,7 @@ export function fsRouter(
       }
       // build only - skip in dev
       if (platformObject.buildOptions?.unstable_phase) {
-        platformObject.buildData ||= {};
-        platformObject.buildData.fsRouterFiles = files;
+        await unstable_setPlatformData('fsRouterFiles', files);
       }
       for (const file of files) {
         const mod = await loadPage(file);

packages/waku/src/server.ts

@@ -1,5 +1,8 @@
 import { getContext } from './middleware/context.js';
 
+// The use of `globalThis` in this file is more or less a hack.
+// It should be revisited with a better solution.
+
 /**
  * This is an internal function and not for public use.
  */
@@ -11,12 +14,49 @@ export function getEnv(key: string): string | undefined {
   return (globalThis as any).__WAKU_SERVER_ENV__?.[key];
 }
 
+/**
+ * This is an internal function and not for public use.
+ */
+export function iterateAllPlatformDataInternal(): Iterable<[string, unknown]> {
+  const platformData: Record<string, unknown> =
+    (globalThis as any).__WAKU_SERVER_PLATFORM_DATA__ || {};
+  return Object.entries(platformData);
+}
+
+/**
+ * This is an internal function and not for public use.
+ */
+export function setPlatformDataLoaderInternal(
+  loader: (key: string) => Promise<unknown>,
+): void {
+  (globalThis as any).__WAKU_SERVER_PLATFORM_DATA_LOADER__ = loader;
+}
+
+// data must be JSON serializable
+export async function unstable_setPlatformData<T>(
+  key: string,
+  data: T,
+): Promise<void> {
+  ((globalThis as any).__WAKU_SERVER_PLATFORM_DATA__ ||= {})[key] = data;
+}
+
+export async function unstable_getPlatformData<T>(
+  key: string,
+): Promise<T | undefined> {
+  const loader: ((key: string) => Promise<unknown>) | undefined = (
+    globalThis as any
+  ).__WAKU_SERVER_PLATFORM_DATA_LOADER__;
+  if (loader) {
+    return loader(key) as T;
+  }
+  return (globalThis as any).__WAKU_SERVER_PLATFORM_DATA__?.[key];
+}
+
 export function unstable_getHeaders(): Readonly<Record<string, string>> {
   return getContext().req.headers;
 }
 
 type PlatformObject = {
-  buildData?: Record<string, unknown>; // must be JSON serializable
   buildOptions?: {
     deploy?:
       | 'vercel-static'
@@ -38,11 +78,9 @@ type PlatformObject = {
   };
 } & Record<string, unknown>;
 
-(globalThis as any).__WAKU_PLATFORM_OBJECT__ ||= {};
-
 // TODO tentative name
 export function unstable_getPlatformObject(): PlatformObject {
-  return (globalThis as any).__WAKU_PLATFORM_OBJECT__;
+  return ((globalThis as any).__WAKU_PLATFORM_OBJECT__ ||= {});
 }
 
 export function unstable_createAsyncIterable<T extends () => unknown>(