[site/content/notes][xs]: note on md hot reload.

site/content/notes/md-hot-reload.md

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+# How it isimplemented in contentlayer
+
+## next-contentlayer
+
+packages/next-contentlayer/src/index.ts
+```js
+import { type NextPluginOptions, runBeforeWebpackCompile } from './plugin.js'
+
+export const defaultPluginOptions: NextPluginOptions = {}
+
+
+export const createContentlayerPlugin =
+  (pluginOptions: NextPluginOptions = defaultPluginOptions) =>
+  (nextConfig: Partial<NextConfig> = {}): Partial<NextConfig> => {
+    return {
+      ...nextConfig,
+      // ...
+      webpack(config: webpack.Configuration, options: any) {
+        config.watchOptions = {
+          ...config.watchOptions,
+          ignored: ['**/node_modules/!(.contentlayer)/**/*'],
+        }
+
+        config.plugins!.push(new ContentlayerWebpackPlugin(pluginOptions))
+
+        // ...
+        return config
+      },
+    }
+  }
+
+// This is what we used to import and use in next.config.js
+export const withContentlayer = createContentlayerPlugin(defaultPluginOptions)
+
+class ContentlayerWebpackPlugin {
+  constructor(readonly pluginOptions: NextPluginOptions) {}
+
+  apply(compiler: webpack.Compiler) {
+    compiler.hooks.beforeCompile.tapPromise('ContentlayerWebpackPlugin', async () => {
+      await runBeforeWebpackCompile({
+        pluginOptions: this.pluginOptions,
+        devServerStartedRef,
+        // this will be `development` when running `next dev`
+        mode: compiler.options.mode,
+      })
+    })
+  }
+}
+```
+
+packages/next-contentlayer/src/plugin.ts
+```js
+export const runBeforeWebpackCompile = async ({
+  mode,
+  pluginOptions,
+  devServerStartedRef,
+}: {
+  mode: WebpackOptionsNormalized['mode']
+  pluginOptions: NextPluginOptions
+  devServerStartedRef: { current: boolean }
+}) => {
+  const isNextDev = mode === 'development'
+  const isBuild = mode === 'production'
+
+  const { configPath } = pluginOptions
+
+  if (isBuild) {
+    checkConstraints()
+    await runContentlayerBuild({ configPath })
+  } else if (isNextDev && !devServerStartedRef.current) {
+    devServerStartedRef.current = true
+    runContentlayerDev({ configPath })
+  }
+}
+
+const runContentlayerDev = async ({ configPath }: NextPluginOptions) => {
+  if (contentlayerInitialized) return
+  contentlayerInitialized = true
+
+  await pipe(
+    core.getConfigWatch({ configPath }),
+    S.tapSkipFirstRight(() => T.log(`Contentlayer config change detected. Updating type definitions and data...`)),
+    S.tapRight((config) => (config.source.options.disableImportAliasWarning ? T.unit : T.fork(core.validateTsconfig))),
+    S.chainSwitchMapEitherRight((config) => core.generateDotpkgStream({ config, verbose: false, isDev: true })),
+    S.tap(E.fold((error) => T.log(errorToString(error)), core.logGenerateInfo)),
+    S.runDrain,
+    runMain,
+  )
+}
+
+const runMain = core.runMain({ tracingServiceName: 'next-contentlayer', verbose: process.env.CL_DEBUG !== undefined })
+
+```
+