Log to console Data Collection flag value and source (#1811)

* Log to console Data Collection flag value and source

This will log the source and value of the `dataCollectionDefaultEnabled` flag.

This is for Issue #1768.

* Put alreadyOutputDataCollectionFlag behind ifdef

This avoids having the property in non-debug builds.

* PR feedback

Added a logging message when explicitly setting the data collection flag.

* Copy-paste error

Fixed a missed change in the ternary check.

Author: bstpierr

Firebase/Core/FIRApp.m

@@ -89,6 +89,10 @@ @interface FIRApp ()
 
 @property(nonatomic) BOOL alreadySentDeleteNotification;
 
+#ifdef DEBUG
+@property(nonatomic) BOOL alreadyOutputDataCollectionFlag;
+#endif  // DEBUG
+
 @end
 
 @implementation FIRApp
@@ -359,6 +363,12 @@ - (FIROptions *)options {
 }
 
 - (void)setDataCollectionDefaultEnabled:(BOOL)dataCollectionDefaultEnabled {
+#ifdef DEBUG
+  FIRLogDebug(kFIRLoggerCore, @"I-COR000034", @"Explicitly %@ data collection flag.",
+              dataCollectionDefaultEnabled ? @"enabled" : @"disabled");
+  self.alreadyOutputDataCollectionFlag = YES;
+#endif  // DEBUG
+
   NSString *key =
       [NSString stringWithFormat:kFIRGlobalAppDataCollectionEnabledDefaultsKeyFormat, self.name];
   [[NSUserDefaults standardUserDefaults] setBool:dataCollectionDefaultEnabled forKey:key];
@@ -385,6 +395,13 @@ - (BOOL)isDataCollectionDefaultEnabled {
   // Check if it's been manually set before in code, and use that as the higher priority value.
   NSNumber *defaultsObject = [[self class] readDataCollectionSwitchFromUserDefaultsForApp:self];
   if (defaultsObject != nil) {
+#ifdef DEBUG
+    if (!self.alreadyOutputDataCollectionFlag) {
+      FIRLogDebug(kFIRLoggerCore, @"I-COR000031", @"Data Collection flag is %@ in user defaults.",
+                  [defaultsObject boolValue] ? @"enabled" : @"disabled");
+      self.alreadyOutputDataCollectionFlag = YES;
+    }
+#endif  // DEBUG
     return [defaultsObject boolValue];
   }
 
@@ -393,9 +410,22 @@ - (BOOL)isDataCollectionDefaultEnabled {
   // no performance impact calling multiple times.
   NSNumber *collectionEnabledPlistValue = [[self class] readDataCollectionSwitchFromPlist];
   if (collectionEnabledPlistValue != nil) {
+#ifdef DEBUG
+    if (!self.alreadyOutputDataCollectionFlag) {
+      FIRLogDebug(kFIRLoggerCore, @"I-COR000032", @"Data Collection flag is %@ in plist.",
+                  [collectionEnabledPlistValue boolValue] ? @"enabled" : @"disabled");
+      self.alreadyOutputDataCollectionFlag = YES;
+    }
+#endif  // DEBUG
     return [collectionEnabledPlistValue boolValue];
   }
 
+#ifdef DEBUG
+  if (!self.alreadyOutputDataCollectionFlag) {
+    FIRLogDebug(kFIRLoggerCore, @"I-COR000033", @"Data Collection flag is not set.");
+    self.alreadyOutputDataCollectionFlag = YES;
+  }
+#endif  // DEBUG
   return YES;
 }