From 3996d496b337b5c7f18d9589f079ed9cb762d2cc Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Mon, 13 Nov 2023 10:17:16 -0800
Subject: [PATCH] Remove limits of ES6 feartures in standard library code

When transpiling to ES5 use closure with `SIMPLE_OPTIMIZATIONS` rather
then `WHITESPACE_ONLY`.  This means that polyfills cant be included
as needed and removes the limits on what ES6 features we can use.

The downside of this is that is slows down builds for ES5 users but
this seems like a reasonable tradeoff.

Fixes: #11984
---
 test/test_other.py | 28 +++++++++++++++++++++-------
 tools/building.py  |  3 ++-
 2 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/test/test_other.py b/test/test_other.py
index 99b5df6235333..cfd636979ac98 100644
--- a/test/test_other.py
+++ b/test/test_other.py
@@ -13002,7 +13002,7 @@ def test_hello_function(self):
   })
   @crossplatform
   def test_es5_transpile(self, args):
-    self.emcc_args += args
+    self.emcc_args += ['-Wno-transpile'] + args
 
     # Create a library file that uses the following ES6 features
     # - let/const
@@ -13018,6 +13018,11 @@ def test_es5_transpile(self, args):
         let obj = Object.assign({}, {prop:1});
         err('prop: ' + obj.prop);
 
+        // for .. of
+        for (var elem of [42, 43]) {
+          err('array elem: ' + elem);
+        }
+
         // arrow funcs + const
         const bar = () => 2;
         err('bar: ' + bar());
@@ -13027,14 +13032,14 @@ def test_es5_transpile(self, args):
         var obj2 = {
           [key]: 42,
         };
-        err('value: ' + obj2[key]);
+        err('computed prop: ' + obj2[key]);
 
         // Method syntax
         var obj3 = {
           myMethod() { return 43 },
         };
         global['foo'] = obj3;
-        err('value2: ' + obj3.myMethod());
+        err('myMethod: ' + obj3.myMethod());
 
         // Nullish coalescing
         var definitely = global['maybe'] ?? {};
@@ -13054,6 +13059,15 @@ def test_es5_transpile(self, args):
       }
     });
     ''')
+    expected = '''\
+prop: 1
+array elem: 42
+array elem: 43
+bar: 2
+computed prop: 42
+myMethod: 43
+'''
+
     create_file('test.c', 'extern void foo(); int main() { foo(); }')
     self.emcc_args += ['--js-library', 'es6_library.js']
     self.uses_es6 = True
@@ -13085,7 +13099,7 @@ def check_for_es6(filename, expect):
     # Check that under normal circumstances none of these features get
     # removed / transpiled.
     print('base case')
-    self.do_runf('test.c', 'prop: 1\nbar: 2\n')
+    self.do_runf('test.c', expected)
     check_for_es6('test.js', True)
 
     # If we select and older browser than closure will kick in by default
@@ -13093,18 +13107,18 @@ def check_for_es6(filename, expect):
     print('with old browser')
     self.emcc_args.remove('-Werror')
     self.set_setting('MIN_CHROME_VERSION', '10')
-    self.do_runf('test.c', 'prop: 1\nbar: 2\n', output_basename='test_old')
+    self.do_runf('test.c', expected, output_basename='test_old')
     check_for_es6('test_old.js', False)
 
     # If we add `--closure=0` that transpiler (closure) is not run at all
     print('with old browser + --closure=0')
-    self.do_runf('test.c', 'prop: 1\nbar: 2\n', emcc_args=['--closure=0'], output_basename='test_no_closure')
+    self.do_runf('test.c', expected, emcc_args=['--closure=0'], output_basename='test_no_closure')
     check_for_es6('test_no_closure.js', True)
 
     # If we use `--closure=1` closure will run in full optimization mode
     # and also transpile to ES5
     print('with old browser + --closure=1')
-    self.do_runf('test.c', 'prop: 1\nbar: 2\n', emcc_args=['--closure=1'], output_basename='test_closure')
+    self.do_runf('test.c', expected, emcc_args=['--closure=1'], output_basename='test_closure')
     check_for_es6('test_closure.js', False)
 
   def test_gmtime_noleak(self):
diff --git a/tools/building.py b/tools/building.py
index dfc357f9300e6..3d1abbb6a25c3 100644
--- a/tools/building.py
+++ b/tools/building.py
@@ -513,7 +513,8 @@ def closure_transpile(filename):
   user_args = []
   closure_cmd, env = get_closure_compiler_and_env(user_args)
   closure_cmd += ['--language_out', 'ES5']
-  closure_cmd += ['--compilation_level', 'WHITESPACE_ONLY']
+  closure_cmd += ['--compilation_level', 'SIMPLE_OPTIMIZATIONS']
+  closure_cmd += ['--formatting', 'PRETTY_PRINT']
   return run_closure_cmd(closure_cmd, filename, env)