Allow optional chaining in JS library code

emcc.py

@@ -2313,6 +2313,8 @@ def phase_linker_setup(options, state, newargs):
                                  settings.MIN_CHROME_VERSION < 49 or
                                  settings.MIN_SAFARI_VERSION < 110000 or
                                  settings.MIN_IE_VERSION != 0x7FFFFFFF)
+    if not feature_matrix.caniuse(feature_matrix.Feature.OPTIONAL_CHAINING):
+      settings.TRANSPILE_TO_ES5 = True
 
     if options.use_closure_compiler is None and settings.TRANSPILE_TO_ES5:
       diagnostics.warning('transpile', 'enabling transpilation via closure due to browser version settings.  This warning can be suppressed by passing `--closure=1` or `--closure=0` to opt into our explicitly.')

src/settings.js

@@ -1764,10 +1764,10 @@ var AUTO_NATIVE_LIBRARIES = true;
 // versions >= MIN_FIREFOX_VERSION
 // are desired to work. Pass -sMIN_FIREFOX_VERSION=majorVersion to drop support
 // for Firefox versions older than < majorVersion.
-// Firefox ESR 68 was released on July 9, 2019.
+// Firefox ESR 74 was released on March 10, 2020
 // MAX_INT (0x7FFFFFFF, or -1) specifies that target is not supported.
 // [link]
-var MIN_FIREFOX_VERSION = 68;
+var MIN_FIREFOX_VERSION = 74;
 
 // Specifies the oldest version of desktop Safari to target. Version is encoded
 // in MMmmVV, e.g. 70101 denotes Safari 7.1.1.
@@ -1806,10 +1806,10 @@ var MIN_EDGE_VERSION = 0x7FFFFFFF;
 
 // Specifies the oldest version of Chrome. E.g. pass -sMIN_CHROME_VERSION=58 to
 // drop support for Chrome 57 and older.
-// Chrome 75.0.3770 was released on 2019-06-04
+// Chrome 80 was released on February 4, 2020
 // MAX_INT (0x7FFFFFFF, or -1) specifies that target is not supported.
 // [link]
-var MIN_CHROME_VERSION = 75;
+var MIN_CHROME_VERSION = 80;
 
 // Specifies minimum node version to target for the generated code.  This is
 // distinct from the minimum version required run the emscripten compiler.

test/test_other.py

@@ -12819,6 +12819,10 @@ def test_es5_transpile(self, args):
         };
         global['foo'] = obj3;
         err('value2: ' + obj3.myMethod());
+
+        // optional chaining
+        let result = Module.foo?.doSomething();
+        err('result: ' + result);
       }
     });
     ''')
@@ -12833,13 +12837,15 @@ def check_for_es6(filename, expect):
         self.assertContained(['() => 2', '()=>2'], js)
         self.assertContained('const ', js)
         self.assertContained('let ', js)
+        self.assertContained('foo?.doSomething()', js)
       else:
         self.verify_es5(filename)
         self.assertNotContained('foo(arg=', js)
         self.assertNotContained('() => 2', js)
         self.assertNotContained('()=>2', js)
         self.assertNotContained('const ', js)
         self.assertNotContained('let ', js)
+        self.assertNotContained('foo?.doSomething()', js)
 
     # Check that under normal circumstances none of these features get
     # removed / transpiled.
@@ -13336,10 +13342,10 @@ def test_reproduce(self):
     self.assertTextDataIdentical(expected, response)
 
   def test_min_browser_version(self):
-    err = self.expect_fail([EMCC, test_file('hello_world.c'), '-Werror', '-sWASM_BIGINT', '-sMIN_SAFARI_VERSION=120000'])
+    err = self.expect_fail([EMCC, test_file('hello_world.c'), '-Werror', '-sWASM_BIGINT', '-sMIN_SAFARI_VERSION=120000', '-Wno-transpile'])
     self.assertContained('emcc: error: MIN_SAFARI_VERSION=120000 is not compatible with WASM_BIGINT (150000 or above required)', err)
 
-    err = self.expect_fail([EMCC, test_file('hello_world.c'), '-Werror', '-pthread', '-sMIN_CHROME_VERSION=73'])
+    err = self.expect_fail([EMCC, test_file('hello_world.c'), '-Werror', '-pthread', '-sMIN_CHROME_VERSION=73', '-Wno-transpile'])
     self.assertContained('emcc: error: MIN_CHROME_VERSION=73 is not compatible with pthreads (74 or above required)', err)
 
   def test_signext_lowering(self):

tools/feature_matrix.py

@@ -23,6 +23,7 @@ class Feature(IntEnum):
   THREADS = auto()
   GLOBALTHIS = auto()
   PROMISE_ANY = auto()
+  OPTIONAL_CHAINING = auto()
 
 
 default_features = {Feature.SIGN_EXT, Feature.MUTABLE_GLOBALS}
@@ -71,6 +72,12 @@ class Feature(IntEnum):
     'safari': 140000,
     'node': 150000,
   },
+  Feature.OPTIONAL_CHAINING: {
+    'chrome': 80,
+    'firefox': 74,
+    'safari': 130400,
+    'node': 140000,
+  },
 }