Bug 1640188 - Add pref and flag to enable Iterator Helpers in nightly, off by default. r=jorendorff

Differential Revision: https://phabricator.services.mozilla.com/D76542

js/public/RealmOptions.h

@@ -228,6 +228,12 @@ class JS_PUBLIC_API RealmCreationOptions {
     return *this;
   }
 
+  bool getIteratorHelpersEnabled() const { return iteratorHelpers_; }
+  RealmCreationOptions& setIteratorHelpersEnabled(bool flag) {
+    iteratorHelpers_ = flag;
+    return *this;
+  }
+
   // This flag doesn't affect JS engine behavior.  It is used by Gecko to
   // mark whether content windows and workers are "Secure Context"s. See
   // https://w3c.github.io/webappsec-secure-contexts/
@@ -267,6 +273,7 @@ class JS_PUBLIC_API RealmCreationOptions {
   bool weakRefs_ = false;
   bool toSource_ = false;
   bool propertyErrorMessageFix_ = false;
+  bool iteratorHelpers_ = false;
   bool secureContext_ = false;
 };
 

js/src/shell/js.cpp

@@ -512,6 +512,7 @@ bool shell::enableReadableStreamPipeTo = false;
 bool shell::enableWeakRefs = false;
 bool shell::enableToSource = false;
 bool shell::enablePropertyErrorMessageFix = false;
+bool shell::enableIteratorHelpers = false;
 #ifdef JS_GC_ZEAL
 uint32_t shell::gZealBits = 0;
 uint32_t shell::gZealFrequency = 0;
@@ -3891,7 +3892,8 @@ static void SetStandardRealmOptions(JS::RealmOptions& options) {
       .setReadableStreamPipeToEnabled(enableReadableStreamPipeTo)
       .setWeakRefsEnabled(enableWeakRefs)
       .setToSourceEnabled(enableToSource)
-      .setPropertyErrorMessageFixEnabled(enablePropertyErrorMessageFix);
+      .setPropertyErrorMessageFixEnabled(enablePropertyErrorMessageFix)
+      .setIteratorHelpersEnabled(enableIteratorHelpers);
 }
 
 static MOZ_MUST_USE bool CheckRealmOptions(JSContext* cx,
@@ -10258,6 +10260,7 @@ static bool SetContextOptions(JSContext* cx, const OptionParser& op) {
   enableToSource = !op.getBoolOption("disable-tosource");
   enablePropertyErrorMessageFix =
       !op.getBoolOption("disable-property-error-message-fix");
+  enableIteratorHelpers = op.getBoolOption("enable-iterator-helpers");
 
   JS::ContextOptionsRef(cx)
       .setAsmJS(enableAsmJS)
@@ -11129,6 +11132,8 @@ int main(int argc, char** argv, char** envp) {
       !op.addBoolOption('\0', "disable-property-error-message-fix",
                         "Disable fix for the error message when accessing "
                         "property of null or undefined") ||
+      !op.addBoolOption('\0', "enable-iterator-helpers",
+                        "Enable iterator helpers") ||
       !op.addStringOption('\0', "shared-memory", "on/off",
                           "SharedArrayBuffer and Atomics "
 #if SHARED_MEMORY_DEFAULT

js/src/shell/jsshell.h

@@ -138,6 +138,7 @@ extern bool enableReadableStreamPipeTo;
 extern bool enableWeakRefs;
 extern bool enableToSource;
 extern bool enablePropertyErrorMessageFix;
+extern bool enableIteratorHelpers;
 #ifdef JS_GC_ZEAL
 extern uint32_t gZealBits;
 extern uint32_t gZealFrequency;

js/xpconnect/src/XPCJSContext.cpp

@@ -758,6 +758,7 @@ static mozilla::Atomic<bool> sStreamsEnabled(false);
 
 static mozilla::Atomic<bool> sPropertyErrorMessageFixEnabled(false);
 static mozilla::Atomic<bool> sWeakRefsEnabled(false);
+static mozilla::Atomic<bool> sIteratorHelpersEnabled(false);
 
 void xpc::SetPrefableRealmOptions(JS::RealmOptions& options) {
   options.creationOptions()
@@ -769,7 +770,8 @@ void xpc::SetPrefableRealmOptions(JS::RealmOptions& options) {
       .setWritableStreamsEnabled(
           StaticPrefs::javascript_options_writable_streams())
       .setPropertyErrorMessageFixEnabled(sPropertyErrorMessageFixEnabled)
-      .setWeakRefsEnabled(sWeakRefsEnabled);
+      .setWeakRefsEnabled(sWeakRefsEnabled)
+      .setIteratorHelpersEnabled(sIteratorHelpersEnabled);
 }
 
 static void LoadStartupJSPrefs(XPCJSContext* xpccx) {
@@ -947,6 +949,8 @@ static void ReloadPrefsCallback(const char* pref, void* aXpccx) {
 #ifdef NIGHTLY_BUILD
   sWeakRefsEnabled =
       Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.weakrefs");
+  sIteratorHelpersEnabled =
+      Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.iterator_helpers");
 #endif
 
 #ifdef JS_GC_ZEAL

modules/libpref/init/StaticPrefList.yaml

@@ -4715,6 +4715,12 @@
   type: RelaxedAtomicBool
   value: false
   mirror: always
+
+  # Experimental support for Iterator Helpers in JavaScript.
+- name: javascript.options.experimental.iterator_helpers
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
 #endif
 
 # The amount of time we wait between a request to GC (due to leaving a page) and doing the actual GC, in ms.