Access filesystem outside of GULHeartbeatDateStorage initializer (#5977)

* Lazily create fileURL

* Changelog

* Added setup check to verify init does not access file system

* Shortened constant name

Author: ncooke3

GoogleUtilities/CHANGELOG.md

@@ -1,4 +1,5 @@
 # 6.7.0 -- M75
+- Lazily access filesystem outside of `GULHeartbeatDateStorage` initializer. (#5969)
 - Update source imports to use repo-relative headers. (#5824)
 - Source cleanups to remove pre-iOS 8 code. (#5841)
 

GoogleUtilities/Environment/GULHeartbeatDateStorage.m

@@ -20,10 +20,14 @@
 @interface GULHeartbeatDateStorage ()
 /** The storage to store the date of the last sent heartbeat. */
 @property(nonatomic, readonly) NSFileCoordinator *fileCoordinator;
+/** The name of the file that stores heartbeat information. */
+@property(nonatomic, readonly) NSString *fileName;
 @end
 
 @implementation GULHeartbeatDateStorage
 
+@synthesize fileURL = _fileURL;
+
 - (instancetype)initWithFileName:(NSString *)fileName {
   if (fileName == nil) {
     return nil;
@@ -32,11 +36,21 @@ - (instancetype)initWithFileName:(NSString *)fileName {
   self = [super init];
   if (self) {
     _fileCoordinator = [[NSFileCoordinator alloc] initWithFilePresenter:nil];
+    _fileName = fileName;
+  }
+  return self;
+}
+
+/** Lazy getter for fileURL
+ * @return fileURL where heartbeat information is stored.
+ */
+- (NSURL *)fileURL {
+  if (!_fileURL) {
     NSURL *directoryURL = [[self class] directoryPathURL];
     [[self class] checkAndCreateDirectory:directoryURL fileCoordinator:_fileCoordinator];
-    _fileURL = [directoryURL URLByAppendingPathComponent:fileName];
+    _fileURL = [directoryURL URLByAppendingPathComponent:_fileName];
   }
-  return self;
+  return _fileURL;
 }
 
 /** Returns the URL path of the Application Support folder.

GoogleUtilities/Example/Tests/Environment/GULHeartbeatDateStorageTest.m

@@ -18,10 +18,11 @@
 #import "GoogleUtilities/Environment/Private/GULHeartbeatDateStorage.h"
 
 @interface GULHeartbeatDateStorageTest : XCTestCase
-@property(nonatomic) NSURL *fileURL;
 @property(nonatomic) GULHeartbeatDateStorage *storage;
 @end
 
+static NSString *const kTestFileName = @"GULStorageHeartbeatTest";
+
 @implementation GULHeartbeatDateStorageTest
 
 - (void)setUp {
@@ -38,7 +39,10 @@ - (void)setUp {
                                                              error:&error],
               @"Error: %@", error);
   }
-  self.storage = [[GULHeartbeatDateStorage alloc] initWithFileName:@"GULStorageHeartbeatTest"];
+
+  self.storage = [[GULHeartbeatDateStorage alloc] initWithFileName:kTestFileName];
+
+  [self assertInitializationDoesNotAccessFileSystem];
 }
 
 - (void)tearDown {
@@ -53,4 +57,24 @@ - (void)testHeartbeatDateForTag {
                  [[self.storage heartbeatDateForTag:@"fire-iid"] timeIntervalSinceReferenceDate]);
 }
 
+#pragma mark - Private Helpers
+
+- (void)assertInitializationDoesNotAccessFileSystem {
+  NSURL *fileURL = [self heartbeatFileURL];
+  NSError *error;
+  BOOL fileIsReachable = [fileURL checkResourceIsReachableAndReturnError:&error];
+  XCTAssertFalse(fileIsReachable,
+                 @"GULHeartbeatDateStorage initialization should not access the file system.");
+  XCTAssertNotNil(error, @"Error: %@", error);
+}
+
+- (NSURL *)heartbeatFileURL {
+  NSString *documentsPath = [NSSearchPathForDirectoriesInDomains(
+      NSApplicationSupportDirectory, NSUserDomainMask, YES) firstObject];
+  NSArray<NSString *> *components = @[ documentsPath, @"Google/FIRApp", kTestFileName ];
+  NSString *fileString = [NSString pathWithComponents:components];
+  NSURL *fileURL = [NSURL fileURLWithPath:fileString];
+  return fileURL;
+}
+
 @end