Bug 1820241 - Use MOZ_ARTIFACT_BUILDS to determine if FOG needs JOG r=glandium,janerik

FOG needs to trigger JOG (artifact build support for runtime-defined metrics.
Allows changes and additions to metrics.yamls to be usable from JS without a
compile step) when running an Artifact Build.

So we take `MOZ_ARTIFACT_BUILDS` and pop it into a pref for FOG's use in C++.

Differential Revision: https://phabricator.services.mozilla.com/D173211

browser/app/profile/firefox.js

@@ -2837,3 +2837,8 @@ pref("cookiebanners.ui.desktop.cfrVariant", 0);
   pref("browser.swipe.navigation-icon-min-radius", 12);
   pref("browser.swipe.navigation-icon-max-radius", 20);
 #endif
+
+// Trigger FOG's Artifact Build support on artifact builds.
+#ifdef MOZ_ARTIFACT_BUILDS
+  pref("telemetry.fog.artifact_build", true);
+#endif

browser/moz.build

@@ -51,6 +51,9 @@ if CONFIG["MOZ_GPSD"]:
 if CONFIG["MOZ_UPDATE_AGENT"]:
     DEFINES["MOZ_UPDATE_AGENT"] = True
 
+if CONFIG["MOZ_ARTIFACT_BUILDS"]:
+    DEFINES["MOZ_ARTIFACT_BUILDS"] = True
+
 # These files are specified in this moz.build to pick up DIST_SUBDIR as set in
 # this directory, which is un-set in browser/app.
 JS_PREFERENCE_PP_FILES += [

modules/libpref/init/StaticPrefList.yaml

@@ -14167,6 +14167,11 @@
   mirror: always
   rust: true
 
+- name: telemetry.fog.artifact_build
+  type: RelaxedAtomicBool
+  value: false
+  mirror: always
+
 #---------------------------------------------------------------------------
 # Prefs starting with "test."
 #---------------------------------------------------------------------------

toolkit/components/glean/bindings/jog/JOG.cpp

@@ -13,7 +13,7 @@
 #include "mozilla/glean/bindings/jog/jog_ffi_generated.h"
 #include "mozilla/Logging.h"
 #include "mozilla/Omnijar.h"
-
+#include "mozilla/StaticPrefs_telemetry.h"
 #include "nsDirectoryServiceDefs.h"
 #include "nsDirectoryServiceUtils.h"
 #include "nsThreadUtils.h"
@@ -44,13 +44,6 @@ static Maybe<bool> sFoundAndLoadedJogfile;
 bool JOG::EnsureRuntimeMetricsRegistered(bool aForce) {
   MOZ_ASSERT(NS_IsMainThread());
 
-#ifdef MOZILLA_OFFICIAL
-  // In the event we're an official build we want there to be no chance we might
-  // accidentally perform I/O on the main thread.
-  MOZ_LOG(sLog, LogLevel::Verbose, ("MOZILLA_OFFICIAL build. No JOG for you."));
-  return false;
-#endif
-
   if (sFoundAndLoadedJogfile) {
     return sFoundAndLoadedJogfile.value();
   }
@@ -58,11 +51,12 @@ bool JOG::EnsureRuntimeMetricsRegistered(bool aForce) {
 
   MOZ_LOG(sLog, LogLevel::Debug, ("Determining whether there's JOG for you."));
 
-  if (mozilla::IsPackagedBuild()) {
+  if (!mozilla::StaticPrefs::telemetry_fog_artifact_build()) {
     // Supporting Artifact Builds is a developer-only thing.
     // We're on the main thread here.
     // Let's not spend any more time than we need to.
-    MOZ_LOG(sLog, LogLevel::Debug, ("IsPackagedBuild. No JOG for you."));
+    MOZ_LOG(sLog, LogLevel::Debug,
+            ("!telemetry.fog.artifact_build. No JOG for you."));
     return false;
   }
   // The metrics we need to process were placed in GreD in jogfile.json

toolkit/components/glean/docs/dev/preferences.md

@@ -38,6 +38,13 @@ Present to allow testing without figuring out how to mock Rust's clock.
 Their values are integer seconds.
 Defaults to 120 (activity), 1200 (inactivity).
 
+## Internal Preferences
+
+`telemetry.fog.artifact_build`
+
+Read-only. This pref is `true` only if `MOZ_ARTIFACT_BUILDS` was set during configure.
+If true, [JOG](./jog) is enabled so that artifact builds will exhibit changes to their Glean metrics.
+
 ## Defines
 
 `MOZ_AUTOMATION`
@@ -72,9 +79,6 @@ This mode can be overridden at runtime in two ways:
   then pings are sent to a server operating locally at that port
   (even if the ping has a Debug Tag), to enable testing.
 
-Also, if set, [JOG](./jog) is disabled.
-Artifact builds will not exhibit changes to their Glean metrics.
-
 `MOZILLA_OFFICIAL` tends to be set on most builds released to users,
 including builds distributed by Linux distributions.
 It tends to not be set on local developer builds.