Expose an async variant of Codegen::forTree()

README.md

@@ -22,7 +22,7 @@ use \Facebook\HackRouter\Codegen;
 
 final class UpdateCodegen {
   public function main(): void {
-    Codegen::forTree(
+    $codegen = await Codegen::forTree(
       __DIR__.'/../src/',
       shape(
         'controllerBase' => WebController::class,
@@ -32,7 +32,8 @@ final class UpdateCodegen {
           'class' => 'Router',
         ),
       ),
-    )->build;
+    );
+    $codegen->build();
   }
 }
 ```

src/Codegen.hack

@@ -96,9 +96,15 @@ final class Codegen {
     self::TCodegenConfig $config,
   ): Codegen {
     // leaving for now as it's a public API
-    /* HHAST_IGNORE_ERROR[DontUseAsioJoin] fix before final release */
-    return
-      new self(\HH\Asio\join(TreeParser::fromPathAsync($source_root)), $config);
+    /* HHAST_IGNORE_ERROR[DontUseAsioJoin] Kept for backward compatibility. */
+    return \HH\Asio\join(static::forTreeAsync($source_root, $config));
+  }
+
+  public static async function forTreeAsync(
+    string $source_root,
+    self::TCodegenConfig $config,
+  ): Awaitable<Codegen> {
+    return new self(await TreeParser::fromPathAsync($source_root), $config);
   }
 
   <<__Memoize>>

tests/CodegenTestCase.hack

@@ -11,9 +11,9 @@ namespace Facebook\HackRouter;
 use function Facebook\FBExpect\expect;
 
 final class CodegenTestCase extends \Facebook\HackTest\HackTest {
-  public function testCanCreateForTree(): void {
+  public async function testCanCreateForTreeAsync(): Awaitable<void> {
     // Just test it parses and we can create an instance
-    $codegen = Codegen::forTree(__DIR__.'/examples/', shape());
+    $codegen = await Codegen::forTreeAsync(__DIR__.'/examples/', shape());
     expect($codegen)->toBeInstanceOf(Codegen::class);
   }
 }