Bug 1894703 - Set logging modules from a single preference r=padenot

This uses a new preference logging.config.modules. When the user sets a
MOZ_LOG string to this preference, it's parsed the same way and the
corresponding modules are enabled.

Differential Revision: https://phabricator.services.mozilla.com/D209249

xpcom/base/LogModulePrefWatcher.cpp

@@ -10,6 +10,7 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/Services.h"
 #include "nsIObserverService.h"
+#include "NSPRLogModulesParser.h"
 #include "nsString.h"
 #include "nsXULAppAPI.h"
 #include "base/process_util.h"
@@ -23,6 +24,7 @@ static const char kLoggingPrefLogFile[] = "logging.config.LOG_FILE";
 static const char kLoggingPrefAddTimestamp[] = "logging.config.add_timestamp";
 static const char kLoggingPrefSync[] = "logging.config.sync";
 static const char kLoggingPrefStacks[] = "logging.config.profilerstacks";
+static const char kLoggingPrefLogModules[] = "logging.config.modules";
 
 namespace mozilla {
 
@@ -85,6 +87,30 @@ static void LoadPrefValue(const char* aName) {
     } else if (prefName.EqualsLiteral(kLoggingPrefStacks)) {
       bool captureStacks = Preferences::GetBool(aName, false);
       LogModule::SetCaptureStacks(captureStacks);
+    } else if (prefName.EqualsLiteral(kLoggingPrefLogModules)) {
+      // The content of the preference will be parsed as a MOZ_LOG string, then
+      // the corresponding log modules (if any) will be enabled, others will be
+      // disabled.
+      LogModule::DisableModules();
+
+      rv = Preferences::GetCString(aName, prefValue);
+      if (NS_FAILED(rv)) {
+        // If the preference is missing, there's nothing to set.
+        return;
+      }
+
+      NSPRLogModulesParser(
+          prefValue.BeginReading(),
+          [](const char* aName, LogLevel aLevel, int32_t aValue) mutable {
+            // Only the special string "profilerstacks" is taken into account,
+            // because we're especially interested in usage with the Firefox
+            // Profiler.
+            if (strcmp(aName, "profilerstacks") == 0) {
+              LogModule::SetCaptureStacks(true);
+            } else {
+              LogModule::Get(aName)->SetLevel(aLevel);
+            }
+          });
     }
     return;
   }

xpcom/base/Logging.cpp

@@ -774,6 +774,13 @@ class LogModuleManager {
     }
   }
 
+  void DisableModules() {
+    OffTheBooksMutexAutoLock guard(mModulesLock);
+    for (auto& m : mModules) {
+      (*(m.GetModifiableData()))->SetLevel(LogLevel::Disabled);
+    }
+  }
+
  private:
   OffTheBooksMutex mModulesLock;
   nsClassHashtable<nsCharPtrHashKey, LogModule> mModules;
@@ -841,6 +848,8 @@ void LogModule::SetCaptureStacks(bool aCaptureStacks) {
   sLogModuleManager->SetCaptureStacks(aCaptureStacks);
 }
 
+void LogModule::DisableModules() { sLogModuleManager->DisableModules(); }
+
 // This function is defined in gecko_logger/src/lib.rs
 // We mirror the level in rust code so we don't get forwarded all of the
 // rust logging and have to create an LogModule for each rust component.

xpcom/base/Logging.h

@@ -125,6 +125,11 @@ class LogModule {
    */
   static void SetCaptureStacks(bool aCaptureStacks);
 
+  /**
+   * Disable all log modules.
+   */
+  static void DisableModules();
+
   /**
    * Indicates whether or not the given log level is enabled.
    */

xpcom/tests/unit/test_logFromPreference.js

@@ -0,0 +1,37 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const kModulesPref = "logging.config.modules";
+add_task(async () => {
+  Services.prefs.setStringPref(kModulesPref, "prof:5");
+  registerCleanupFunction(() => {
+    Services.prefs.clearUserPref(kModulesPref);
+  });
+
+  const entries = 10000;
+  const interval = 1;
+  const threads = ["GeckoMain"];
+  const features = ["nostacksampling"];
+  await Services.profiler.StartProfiler(entries, interval, features, threads);
+  const profileData = await Services.profiler.getProfileDataAsync();
+  await Services.profiler.StopProfiler();
+  const { markers, stringTable } = profileData.threads[0];
+  const stringIndexForLogMessages = stringTable.indexOf("LogMessages");
+  Assert.greaterOrEqual(
+    stringIndexForLogMessages,
+    0,
+    "A string index for the string LogMessages have been found."
+  );
+
+  // At least one log for the profiler json streaming operation should exist.
+  // See https://searchfox.org/mozilla-central/rev/445a6e86233c733c5557ef44e1d33444adaddefc/mozglue/baseprofiler/core/platform.cpp#2015
+  const logMessageMarkers = markers.data.filter(
+    tuple => tuple[markers.schema.name] === stringIndexForLogMessages
+  );
+
+  Assert.greaterOrEqual(
+    logMessageMarkers.length,
+    0,
+    "At least one log message have been found."
+  );
+});

xpcom/tests/unit/xpcshell.toml

@@ -58,6 +58,9 @@ fail-if = ["os == 'android'"]
 
 ["test_localfile.js"]
 
+["test_logFromPreference.js"]
+skip-if = "(os == 'android' && release_or_beta)" # bug 1841818
+
 ["test_mac_bundle.js"]
 
 ["test_mac_xattrs.js"]