Bug 1732358 - Part 2: Add the ability to force-disable fission with a…

…n environment variable, r=ahal,fluent-reviewers,flod,mccr8

This is required to replace the existing MOZ_FORCE_ENABLE_FISSION environment
variables in environments which use that. In the future we'll want to stop
passing any environment variable when not passing a flag to `./mach run`
however that will require changes to the default test behaviour in bug 1744091.

Differential Revision: https://phabricator.services.mozilla.com/D133006

mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/util/Environment.java

@@ -62,6 +62,9 @@ public boolean isX86() {
   }
 
   public boolean isFission() {
+    // NOTE: This isn't accurate, as it doesn't take into account the default
+    // value of the pref or environment variables like
+    // `MOZ_FORCE_DISABLE_FISSION`.
     return getEnvVar("MOZ_FORCE_ENABLE_FISSION").equals("1");
   }
 

python/mozbuild/mozbuild/mach_commands.py

@@ -1331,6 +1331,8 @@ def _run_android(
                     'Using profile from target "{target_profile}"',
                 )
 
+        # FIXME: When android switches to using Fission by default,
+        # MOZ_FORCE_DISABLE_FISSION will need to be configured correctly.
         if enable_fission:
             env.append("MOZ_FORCE_ENABLE_FISSION=1")
 
@@ -1778,6 +1780,8 @@ def _run_desktop(
 
     if enable_fission:
         extra_env["MOZ_FORCE_ENABLE_FISSION"] = "1"
+    else:
+        extra_env["MOZ_FORCE_DISABLE_FISSION"] = "1"
 
     if some_debugging_option:
         if "INSIDE_EMACS" in os.environ:

testing/mochitest/runjunit.py

@@ -242,6 +242,8 @@ def build_command_line(self, test_filters_file, test_filters):
             env["MOZ_WEBRENDER"] = "1"
         else:
             env["MOZ_WEBRENDER"] = "0"
+        # FIXME: When android switches to using Fission by default,
+        # MOZ_FORCE_DISABLE_FISSION will need to be configured correctly.
         if self.options.enable_fission:
             env["MOZ_FORCE_ENABLE_FISSION"] = "1"
         # Add additional env variables

toolkit/content/aboutSupport.js

@@ -148,6 +148,7 @@ var snapshotFormatters = {
       experimentTreatment: "fission-status-experiment-treatment",
       disabledByE10sEnv: "fission-status-disabled-by-e10s-env",
       enabledByEnv: "fission-status-enabled-by-env",
+      disabledByEnv: "fission-status-disabled-by-env",
       disabledBySafeMode: "fission-status-disabled-by-safe-mode",
       enabledByDefault: "fission-status-enabled-by-default",
       disabledByDefault: "fission-status-disabled-by-default",

toolkit/locales/en-US/toolkit/about/aboutSupport.ftl

@@ -343,6 +343,7 @@ fission-status-experiment-control = Disabled by experiment
 fission-status-experiment-treatment = Enabled by experiment
 fission-status-disabled-by-e10s-env = Disabled by environment
 fission-status-enabled-by-env = Enabled by environment
+fission-status-disabled-by-env = Disabled by environment
 fission-status-disabled-by-safe-mode = Disabled by safe mode
 fission-status-enabled-by-default = Enabled by default
 fission-status-disabled-by-default = Disabled by default

toolkit/xre/nsAppRunner.cpp

@@ -707,6 +707,9 @@ static void EnsureFissionAutostartInitialized() {
   } else if (EnvHasValue("MOZ_FORCE_ENABLE_FISSION")) {
     gFissionAutostart = true;
     gFissionDecisionStatus = nsIXULRuntime::eFissionEnabledByEnv;
+  } else if (EnvHasValue("MOZ_FORCE_DISABLE_FISSION")) {
+    gFissionAutostart = false;
+    gFissionDecisionStatus = nsIXULRuntime::eFissionDisabledByEnv;
   } else {
     // NOTE: This will take into account changes to the default due to
     // `InitializeFissionExperimentStatus`.
@@ -1109,6 +1112,9 @@ nsXULAppInfo::GetFissionDecisionStatusString(nsACString& aResult) {
     case eFissionEnabledByEnv:
       aResult = "enabledByEnv";
       break;
+    case eFissionDisabledByEnv:
+      aResult = "disabledByEnv";
+      break;
     case eFissionDisabledBySafeMode:
       aResult = "disabledBySafeMode";
       break;

toolkit/xre/test/marionette/test_fission_autostart.py

@@ -19,6 +19,7 @@ class Prefs:
 
 
 ENV_ENABLE_FISSION = "MOZ_FORCE_ENABLE_FISSION"
+ENV_DISABLE_FISSION = "MOZ_FORCE_DISABLE_FISSION"
 ENV_DISABLE_E10S = "MOZ_FORCE_DISABLE_E10S"
 
 
@@ -27,12 +28,13 @@ class Prefs:
     "experimentTreatment": 2,
     "disabledByE10sEnv": 3,
     "enabledByEnv": 4,
-    "disabledBySafeMode": 5,
-    "enabledByDefault": 6,
-    "disabledByDefault": 7,
-    "enabledByUserPref": 8,
-    "disabledByUserPref": 9,
-    "disabledByE10sOther": 10,
+    "disabledByEnv": 5,
+    "disabledBySafeMode": 6,
+    "enabledByDefault": 7,
+    "disabledByDefault": 8,
+    "enabledByUserPref": 9,
+    "disabledByUserPref": 10,
+    "disabledByE10sOther": 11,
 }
 
 

xpcom/system/nsIXULRuntime.idl

@@ -19,8 +19,8 @@ uint32_t GetMaxWebProcessCount();
 // global value of the pref. For other use cases, you should use
 // nsILoadContext::UseRemoteSubframes instead. This will also check for special
 // conditions, like safe mode, which may require fission to be disabled, or
-// environment variable MOZ_FORCE_ENABLE_FISSION, used by mach run to
-// enable fission regardless of pref settings.
+// environment variables MOZ_FORCE_ENABLE_FISSION and MOZ_FORCE_DISABLE_FISSION,
+// used by mach run to enable/disable fission regardless of pref settings.
 bool FissionAutostart();
 
 // Returns whether or not we are currently enrolled in the fission experiment.
@@ -88,25 +88,28 @@ interface nsIXULRuntime : nsISupports
     // Fission is enabled because the `MOZ_FORCE_ENABLE_FISSION` environment
     // variable is set.
     eFissionEnabledByEnv = 4,
+    // Fission is disabled because the `MOZ_FORCE_DISABLE_FISSION` environment
+    // variable is set.
+    eFissionDisabledByEnv = 5,
     // Fission is disabled because the current session is running in safe
     // mode.
-    eFissionDisabledBySafeMode = 5,
+    eFissionDisabledBySafeMode = 6,
     // Fission is enabled because the "fission.autostart" preference is true
     // by default.
-    eFissionEnabledByDefault = 6,
+    eFissionEnabledByDefault = 7,
     // Fission is disabled because the "fission.autostart" preference is false
     // by default.
-    eFissionDisabledByDefault = 7,
+    eFissionDisabledByDefault = 8,
     // Fission is enabled because the "fission.autostart" preference was
     // turned on by the user.
-    eFissionEnabledByUserPref = 8,
+    eFissionEnabledByUserPref = 9,
     // Fission is enabled because the "fission.autostart" preference was
     // turned on by the user.
-    eFissionDisabledByUserPref = 9,
+    eFissionDisabledByUserPref = 10,
     // Fission is disabled because e10s is disabled for some other reason.
-    eFissionDisabledByE10sOther = 10,
+    eFissionDisabledByE10sOther = 11,
     // Fission is enabled by a Normandy phased rollout.
-    eFissionEnabledByRollout = 11,
+    eFissionEnabledByRollout = 12,
   };
 
   /**