From 569ad0aa38245bb6a4155a54fccce47ffb97c0ca Mon Sep 17 00:00:00 2001
From: Natalie Weizenbaum <nweiz@google.com>
Date: Fri, 9 Jun 2023 16:31:08 -0700
Subject: [PATCH] Re-enable support for default exports

See #2008
---
 CHANGELOG.md          |  6 ++++++
 tool/grind.dart       | 38 ++++++++++++++++++++++++++++++++++++++
 tool/grind/utils.dart | 20 ++++++++++++++++++++
 3 files changed, 64 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 747deb5d2..283e58b3a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 ## 1.63.4
 
+### JavaScript API
+
+* Re-enable support for `import sass from 'sass'` when loading the package from
+  an ESM module. However, this syntax is now deprecated; ESM users should use
+  `import * as sass from 'sass'` instead.
+
 ### Embedded Sass
 
 * Fix a race condition where closing standard input while requests are in-flight
diff --git a/tool/grind.dart b/tool/grind.dart
index 84bec47c6..95cd60a8b 100644
--- a/tool/grind.dart
+++ b/tool/grind.dart
@@ -101,6 +101,10 @@ void main(List<String> args) {
   };
 
   pkg.addAllTasks();
+
+  afterTask("pkg-npm-dev", _addDefaultExport);
+  afterTask("pkg-npm-release", _addDefaultExport);
+
   grind(args);
 }
 
@@ -243,3 +247,37 @@ dart run protoc_plugin "\$@"
             Platform.environment["PATH"]!
       }));
 }
+
+/// After building the NPM package, add default exports to
+/// `build/npm/sass.node.mjs`.
+///
+/// See sass/dart-sass#2008.
+void _addDefaultExport() {
+  var buffer = StringBuffer();
+buffer.writeln(File("build/npm/sass.node.mjs").readAsStringSync());
+
+buffer.writeln("""
+let printedDefaultExportDeprecation = false;
+function defaultExportDeprecation() {
+  if (printedDefaultExportDeprecation) return;
+  printedDefaultExportDeprecation = true;
+  console.error(
+      "`import sass from 'sass'` is deprecated.\\n" +
+      "Please use `import * as sass from 'sass'` instead.");
+}
+""");
+
+buffer.writeln("export default {");
+for (var export in pkg.jsEsmExports.value!) {
+  buffer.write("""
+  get $export() {
+    defaultExportDeprecation();
+    return _cliPkgExports.$export;
+  },
+""");
+}
+
+buffer.writeln("};");
+
+File("build/npm/sass.node.mjs").writeAsStringSync(buffer.toString());
+}
diff --git a/tool/grind/utils.dart b/tool/grind/utils.dart
index 1135865ee..9d230cb0a 100644
--- a/tool/grind/utils.dart
+++ b/tool/grind/utils.dart
@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ -9,6 +10,9 @@ import 'package:cli_pkg/cli_pkg.dart' as pkg;
 import 'package:grinder/grinder.dart';
 import 'package:path/path.dart' as p;
 
+// Work around the lack of google/grinder.dart#402.
+import 'package:grinder/src/singleton.dart';
+
 /// Options for [run] that tell Git to commit using SassBot's name and email.
 final sassBotEnvironment = RunOptions(environment: {
   "GIT_AUTHOR_NAME": pkg.botName.value,
@@ -75,3 +79,19 @@ String cloneOrCheckout(String url, String ref, {String? name}) {
 
   return path;
 }
+
+/// Registers [callback] to run after the task named [taskName].
+///
+/// This must be called after the base [taskName] is registered.
+void afterTask(String taskName, FutureOr<void> callback()) {
+  // This takes advantage of the fact that Grinder's task list is mutable to
+  // override the existing task with our new one.
+  var index = grinder.tasks.indexWhere((task) => task.name == taskName);
+  if (index == -1) fail("There is no task named $taskName.");
+
+  var oldTask = grinder.tasks[index];
+  grinder.tasks[index] = GrinderTask(taskName, description: oldTask.description, depends: oldTask.depends, taskFunction: (TaskArgs args) async {
+    await oldTask.execute(context, args);
+    await callback();
+  });
+}