fix(oxide): retain Windows addon after worker exit

crates/node/src/lib.rs

@@ -5,6 +5,38 @@ extern crate napi_derive;
 
 mod utf16;
 
+#[cfg(windows)]
+#[napi(module_exports)]
+fn retain_native_library() -> napi::Result<()> {
+  use std::ffi::c_void;
+
+  #[link(name = "kernel32")]
+  extern "system" {
+    fn GetModuleHandleExW(flags: u32, address: *const u16, module: *mut *mut c_void) -> i32;
+  }
+
+  const FROM_ADDRESS: u32 = 0x00000004;
+  const PIN: u32 = 0x00000001;
+  let mut module = std::ptr::null_mut();
+  // Rayon threads may outlive a Node worker. Keep their code mapped until process exit.
+  // SAFETY: FROM_ADDRESS treats this function's address as a module location, not a string.
+  // The module is executing this registration hook and `module` is a valid output pointer.
+  let retained = unsafe {
+    GetModuleHandleExW(
+      FROM_ADDRESS | PIN,
+      retain_native_library as *const () as *const u16,
+      &mut module,
+    )
+  };
+  if retained == 0 {
+    return Err(napi::Error::from_reason(format!(
+      "Failed to retain the Oxide native library: {}",
+      std::io::Error::last_os_error()
+    )));
+  }
+  Ok(())
+}
+
 #[derive(Debug, Clone)]
 #[napi(object)]
 pub struct ChangedContent {

integrations/oxide/workers.test.ts

@@ -1,7 +1,7 @@
 import { js, json, test } from '../utils'
 
 test(
-  '@tailwindcss/oxide can be loaded into a Node.js worker thread',
+  '@tailwindcss/oxide can scan in a Node.js worker and survive worker exit',
   {
     fs: {
       'package.json': json`
@@ -12,21 +12,43 @@ test(
         }
       `,
       'start.js': js`
+        let assert = require('node:assert/strict')
         let { Worker } = require('worker_threads')
-        new Worker('./worker.js')
+        let worker = new Worker('./worker.js')
+        worker.on('error', (error) => {
+          throw error
+        })
+        worker.on('exit', (code) => {
+          assert.equal(code, 0)
+          if (process.platform === 'win32') {
+            assert.ok(
+              process.report
+                .getReport()
+                .sharedObjects.some((file) => /tailwindcss-oxide.*[.]node$/.test(file)),
+              'Oxide must remain mapped after the worker exits',
+            )
+          }
+          setTimeout(() => console.log('parent survived worker exit'), 500)
+        })
       `,
       'worker.js': js`
-        require('@tailwindcss/oxide')
+        let assert = require('node:assert/strict')
+        let { Scanner } = require('@tailwindcss/oxide')
+        let scanner = new Scanner({ sources: [] })
+        let candidates = scanner.scanFiles(
+          Array.from({ length: 100 }, () => ({
+            content: '<div class="flex p-4 text-red-500"></div>',
+            extension: 'html',
+          })),
+        )
+        assert.ok(candidates.includes('flex'))
         process.on('exit', () => console.log('worker thread exited'))
       `,
     },
   },
   async ({ exec, expect }) => {
-    let output = await exec('node ./start.js').then(
-      (out) => out.trim(),
-      (err) => `${err}`,
-    )
+    let output = await exec('node ./start.js').then((out) => out.trim())
 
-    expect(output).toEqual('worker thread exited')
+    expect(output).toEqual('worker thread exited\nparent survived worker exit')
   },
 )