Clean up data source temp files when complete.

// FREEBIE

Signal/src/ViewControllers/ConversationView/ConversationViewController.m

@@ -3480,6 +3480,8 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
                                     id<DataSource> _Nullable dataSource =
                                         [DataSourcePath dataSourceWithURL:compressedVideoUrl];
                                     [dataSource setSourceFilename:filename];
+                                    // Remove temporary file when complete.
+                                    [dataSource setShouldDeleteOnDeallocation];
                                     SignalAttachment *attachment =
                                         [SignalAttachment attachmentWithDataSource:dataSource
                                                                            dataUTI:(NSString *)kUTTypeMPEG4];
@@ -3523,6 +3525,8 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
 
 - (void)yapDatabaseModified:(NSNotification *)notification
 {
+    OWSAssert([NSThread isMainThread]);
+
     // Currently, we update thread and message state every time
     // the database is modified.  That doesn't seem optimal, but
     // in practice it's efficient enough.
@@ -3642,6 +3646,8 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
         }
     }
         completion:^(BOOL success) {
+            OWSAssert([NSThread isMainThread]);
+
             if (!success) {
                 [self resetContentAndLayout];
             }
@@ -3871,6 +3877,8 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
     NSString *filename = [NSLocalizedString(@"VOICE_MESSAGE_FILE_NAME", @"Filename for voice messages.")
         stringByAppendingPathExtension:@"m4a"];
     [dataSource setSourceFilename:filename];
+    // Remove temporary file when complete.
+    [dataSource setShouldDeleteOnDeallocation];
     SignalAttachment *attachment =
         [SignalAttachment voiceMessageAttachmentWithDataSource:dataSource dataUTI:(NSString *)kUTTypeMPEG4Audio];
     if (!attachment || [attachment hasError]) {

SignalServiceKit/src/Util/DataSource.h

@@ -40,6 +40,10 @@ NS_ASSUME_NONNULL_BEGIN
 - (nullable NSString *)sourceFilename;
 - (void)setSourceFilename:(NSString *_Nullable)sourceFilename;
 
+// If called, this data source will try to delete its on-disk contents
+// when it is deallocated.
+- (void)setShouldDeleteOnDeallocation;
+
 @end
 
 #pragma mark -

SignalServiceKit/src/Util/DataSource.m

@@ -18,12 +18,30 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (nonatomic, nullable) NSString *sourceFilename;
 
+@property (nonatomic) BOOL shouldDeleteOnDeallocation;
+
 @end
 
 #pragma mark -
 
 @implementation DataSourceValue
 
+- (void)dealloc
+{
+    if (self.shouldDeleteOnDeallocation) {
+        NSString *filePath = self.cachedFilePath;
+        if (filePath) {
+            dispatch_async(dispatch_get_main_queue(), ^{
+                NSError *error;
+                BOOL success = [[NSFileManager defaultManager] removeItemAtPath:filePath error:&error];
+                if (!success || error) {
+                    OWSCFail(@"DataSourceValue could not delete file: %@, %@", filePath, error);
+                }
+            });
+        }
+    }
+}
+
 + (nullable id<DataSource>)dataSourceWithData:(NSData *)data fileExtension:(NSString *)fileExtension
 {
     OWSAssert(data);
@@ -35,6 +53,8 @@ NS_ASSUME_NONNULL_BEGIN
     DataSourceValue *instance = [DataSourceValue new];
     instance.dataValue = data;
     instance.fileExtension = fileExtension;
+    // Always try to clean up temp files created by this instance.
+    [instance setShouldDeleteOnDeallocation];
     return instance;
 }
 
@@ -89,7 +109,6 @@ NS_ASSUME_NONNULL_BEGIN
             NSString *dirPath = NSTemporaryDirectory();
             NSString *fileName = [[[NSUUID UUID] UUIDString] stringByAppendingPathExtension:self.fileExtension];
             NSString *filePath = [dirPath stringByAppendingPathComponent:fileName];
-            DDLogError(@"%@ ---- writing data", self.tag);
             if ([self writeToPath:filePath]) {
                 self.cachedFilePath = filePath;
             } else {
@@ -131,6 +150,11 @@ NS_ASSUME_NONNULL_BEGIN
     }
 }
 
+- (void)setShouldDeleteOnDeallocation
+{
+    self.shouldDeleteOnDeallocation = YES;
+}
+
 #pragma mark - Logging
 
 + (NSString *)tag
@@ -157,12 +181,30 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (nonatomic, nullable) NSString *sourceFilename;
 
+@property (nonatomic) BOOL shouldDeleteOnDeallocation;
+
 @end
 
 #pragma mark -
 
 @implementation DataSourcePath
 
+- (void)dealloc
+{
+    if (self.shouldDeleteOnDeallocation) {
+        NSString *filePath = self.filePath;
+        if (filePath) {
+            dispatch_async(dispatch_get_main_queue(), ^{
+                NSError *error;
+                BOOL success = [[NSFileManager defaultManager] removeItemAtPath:filePath error:&error];
+                if (!success || error) {
+                    OWSCFail(@"DataSourcePath could not delete file: %@, %@", filePath, error);
+                }
+            });
+        }
+    }
+}
+
 + (nullable id<DataSource>)dataSourceWithURL:(NSURL *)fileUrl;
 {
     OWSAssert(fileUrl);
@@ -263,6 +305,11 @@ NS_ASSUME_NONNULL_BEGIN
     }
 }
 
+- (void)setShouldDeleteOnDeallocation
+{
+    self.shouldDeleteOnDeallocation = YES;
+}
+
 #pragma mark - Logging
 
 + (NSString *)tag