deprecate cjs and add warning similar to vite

README.md

@@ -48,6 +48,13 @@ import { extract } from 'https://esm.sh/@extractus/feed-extractor'
 
 Please check [the examples](https://github.com/extractus/feed-extractor/tree/main/examples) for reference.
 
+## CJS Deprecated
+
+CJS is deprecated for this package.  When calling `require('@extractus/feed-extractor')` a deprecation warning is now logged.  You should update your code to use the ESM export.
+
+- You can ignore this warning via the environment variable `FEED_EXTRACTOR_CJS_IGNORE_WARNING=true`
+- To see where the warning is coming from you can set the environment variable `FEED_EXTRACTOR_CJS_TRACE_WARNING=true`
+
 
 ## APIs
 

build.js

@@ -9,7 +9,7 @@ const externalDeps = Object.keys(dependencies)
   .filter(dep => !esmDependencies.has(dep))
 
 build({
-  entryPoints: ['./src/main.js'],
+  entryPoints: ['./src/cjs-entry.js'],
   bundle: true,
   platform: 'node',
   target: 'node16',

src/cjs-entry.js

@@ -0,0 +1,14 @@
+function warnCjsUsage () {
+  if (process.env.FEED_EXTRACTOR_CJS_IGNORE_WARNING?.toLowerCase() === 'true') return
+  const yellow = (str) => `\u001b[33m${str}\u001b[39m`
+  const log = process.env.FEED_EXTRACTOR_CJS_TRACE_WARNING?.toLowerCase() === 'true' ? console.trace : console.warn
+  log(
+    yellow(
+      'The CJS build of @extractus/feed-extractor is deprecated. See https://github.com/extractus/feed-extractor#cjs-deprecated for details.'
+    )
+  )
+}
+
+warnCjsUsage()
+
+export * from './main'