Bug 1259822 - Part 1: Add pref to enable fix for accessing property of null or undefined. r=jorendorff

Differential Revision: https://phabricator.services.mozilla.com/D58103

--HG--
extra : moz-landing-system : lando

js/public/RealmOptions.h

@@ -191,6 +191,14 @@ class JS_PUBLIC_API RealmCreationOptions {
     return *this;
   }
 
+  bool getPropertyErrorMessageFixEnabled() const {
+    return propertyErrorMessageFix_;
+  }
+  RealmCreationOptions& setPropertyErrorMessageFixEnabled(bool flag) {
+    propertyErrorMessageFix_ = 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/
@@ -230,6 +238,7 @@ class JS_PUBLIC_API RealmCreationOptions {
   bool awaitFix_ = false;
   bool weakRefs_ = false;
   bool toSource_ = false;
+  bool propertyErrorMessageFix_ = false;
   bool secureContext_ = false;
 };
 

js/src/shell/js.cpp

@@ -500,6 +500,7 @@ bool shell::enableFields = false;
 bool shell::enableAwaitFix = false;
 bool shell::enableWeakRefs = false;
 bool shell::enableToSource = false;
+bool shell::enablePropertyErrorMessageFix = false;
 #ifdef JS_GC_ZEAL
 uint32_t shell::gZealBits = 0;
 uint32_t shell::gZealFrequency = 0;
@@ -3715,7 +3716,8 @@ static void SetStandardRealmOptions(JS::RealmOptions& options) {
       .setFieldsEnabled(enableFields)
       .setAwaitFixEnabled(enableAwaitFix)
       .setWeakRefsEnabled(enableWeakRefs)
-      .setToSourceEnabled(enableToSource);
+      .setToSourceEnabled(enableToSource)
+      .setPropertyErrorMessageFixEnabled(enablePropertyErrorMessageFix);
   options.behaviors().setDeferredParserAlloc(enableDeferredMode);
 }
 
@@ -10388,6 +10390,8 @@ static bool SetContextOptions(JSContext* cx, const OptionParser& op) {
   enableAwaitFix = op.getBoolOption("enable-experimental-await-fix");
   enableWeakRefs = op.getBoolOption("enable-weak-refs");
   enableToSource = !op.getBoolOption("disable-tosource");
+  enablePropertyErrorMessageFix =
+      !op.getBoolOption("disable-property-error-message-fix");
 
   JS::ContextOptionsRef(cx)
       .setAsmJS(enableAsmJS)
@@ -11187,6 +11191,9 @@ int main(int argc, char** argv, char** envp) {
                         "Enable new, faster await semantics") ||
       !op.addBoolOption('\0', "enable-weak-refs", "Enable weak references") ||
       !op.addBoolOption('\0', "disable-tosource", "Disable toSource/uneval") ||
+      !op.addBoolOption('\0', "disable-property-error-message-fix",
+                        "Disable fix for the error message when accessing "
+                        "property of null or undefined") ||
       !op.addStringOption('\0', "shared-memory", "on/off",
                           "SharedArrayBuffer and Atomics "
 #if SHARED_MEMORY_DEFAULT

js/src/shell/jsshell.h

@@ -125,6 +125,7 @@ extern bool enableFields;
 extern bool enableAwaitFix;
 extern bool enableWeakRefs;
 extern bool enableToSource;
+extern bool enablePropertyErrorMessageFix;
 #ifdef JS_GC_ZEAL
 extern uint32_t gZealBits;
 extern uint32_t gZealFrequency;

js/xpconnect/src/XPCJSContext.cpp

@@ -760,6 +760,7 @@ static mozilla::Atomic<bool> sStreamsEnabled(false);
 static mozilla::Atomic<bool> sFieldsEnabled(false);
 static mozilla::Atomic<bool> sParserDeferAllocationEnabled(false);
 static mozilla::Atomic<bool> sAwaitFixEnabled(false);
+static mozilla::Atomic<bool> sPropertyErrorMessageFixEnabled(false);
 
 void xpc::SetPrefableRealmOptions(JS::RealmOptions& options) {
   options.creationOptions()
@@ -771,7 +772,8 @@ void xpc::SetPrefableRealmOptions(JS::RealmOptions& options) {
       .setWritableStreamsEnabled(
           StaticPrefs::javascript_options_writable_streams())
       .setFieldsEnabled(sFieldsEnabled)
-      .setAwaitFixEnabled(sAwaitFixEnabled);
+      .setAwaitFixEnabled(sAwaitFixEnabled)
+      .setPropertyErrorMessageFixEnabled(sPropertyErrorMessageFixEnabled);
   options.behaviors().setDeferredParserAlloc(sParserDeferAllocationEnabled);
 }
 
@@ -939,6 +941,8 @@ static void ReloadPrefsCallback(const char* pref, void* aXpccx) {
       Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.fields");
   sAwaitFixEnabled =
       Preferences::GetBool(JS_OPTIONS_DOT_STR "experimental.await_fix");
+  sPropertyErrorMessageFixEnabled =
+      Preferences::GetBool(JS_OPTIONS_DOT_STR "property_error_message_fix");
 
 #ifdef DEBUG
   sExtraWarningsForSystemJS =

modules/libpref/init/StaticPrefList.yaml

@@ -4183,6 +4183,12 @@
   value: true
   mirror: always
 
+# Use better error message when accessing property of null or undefined.
+- name: javascript.options.property_error_message_fix
+  type: RelaxedAtomicBool
+  value: @IS_NOT_RELEASE_OR_BETA@
+  mirror: always
+
 # The amount of time we wait between a request to GC (due to leaving a page) and doing the actual GC, in ms.
 - name: javascript.options.gc_delay
   type: uint32_t