Bug 1293205 - Part 1: Warn about non-standard for-each regardless of JS version number. r=evilpie

js/src/frontend/Parser.cpp

@@ -5220,10 +5220,8 @@ Parser<ParseHandler>::forStatement(YieldHandling yieldHandling)
             iflags = JSITER_FOREACH;
             isForEach = true;
             addTelemetry(JSCompartment::DeprecatedForEach);
-            if (versionNumber() < JSVERSION_LATEST) {
-                if (!report(ParseWarning, pc->sc()->strict(), null(), JSMSG_DEPRECATED_FOR_EACH))
-                    return null();
-            }
+            if (!warnOnceAboutForEach())
+                return null();
         }
     }
 
@@ -9032,6 +9030,22 @@ Parser<ParseHandler>::warnOnceAboutExprClosure()
     return true;
 }
 
+template <typename ParseHandler>
+bool
+Parser<ParseHandler>::warnOnceAboutForEach()
+{
+    JSContext* cx = context->maybeJSContext();
+    if (!cx)
+        return true;
+
+    if (!cx->compartment()->warnedAboutForEach) {
+        if (!report(ParseWarning, false, null(), JSMSG_DEPRECATED_FOR_EACH))
+            return false;
+        cx->compartment()->warnedAboutForEach = true;
+    }
+    return true;
+}
+
 template class Parser<FullParseHandler>;
 template class Parser<SyntaxParseHandler>;
 

js/src/frontend/Parser.h

@@ -1340,6 +1340,7 @@ class Parser final : private JS::AutoGCRooter, public StrictModeGetter
     void addTelemetry(JSCompartment::DeprecatedLanguageExtension e);
 
     bool warnOnceAboutExprClosure();
+    bool warnOnceAboutForEach();
 };
 
 } /* namespace frontend */

js/src/jit-test/tests/parser/for-each-warn.js

@@ -0,0 +1,36 @@
+// for-each should be warned once and only once.
+
+function testWarn(code) {
+  enableLastWarning();
+  var g = newGlobal();
+  g.code = code;
+  g.eval('eval(code)');
+  var warning = getLastWarning();
+  assertEq(warning !== null, true, "warning should be caught for " + code);
+  assertEq(warning.name, "Warning");
+
+  clearLastWarning();
+  g.eval('eval(code)');
+  warning = getLastWarning();
+  assertEq(warning, null, "warning should not be caught for 2nd ocurrence");
+
+  clearLastWarning();
+  g = newGlobal();
+  g.code = code;
+  g.eval('Reflect.parse(code);');
+  warning = getLastWarning();
+  assertEq(warning !== null, true, "warning should be caught for " + code);
+  assertEq(warning.name, "Warning");
+
+  clearLastWarning();
+  g.eval('Reflect.parse(code);');
+  warning = getLastWarning();
+  assertEq(warning, null, "warning should not be caught for 2nd ocurrence");
+  disableLastWarning();
+}
+
+testWarn("for each (var x in {}) {}");
+testWarn("for each (x in {}) {}");
+testWarn("for each (let y in {}) {}");
+testWarn("for each (const y in {}) {}");
+testWarn("for each ([x, y] in {}) {}");

js/src/jscompartment.cpp

@@ -53,6 +53,7 @@ JSCompartment::JSCompartment(Zone* zone, const JS::CompartmentOptions& options =
     isSelfHosting(false),
     marked(true),
     warnedAboutExprClosure(false),
+    warnedAboutForEach(false),
 #ifdef DEBUG
     firedOnNewGlobalObject(false),
 #endif

js/src/jscompartment.h

@@ -338,6 +338,7 @@ struct JSCompartment
     bool                         isSelfHosting;
     bool                         marked;
     bool                         warnedAboutExprClosure;
+    bool                         warnedAboutForEach;
 
 #ifdef DEBUG
     bool                         firedOnNewGlobalObject;