TimedRollingFileTree doesn't handle log directories properly

[dominicmh]

Problem

Using TimedRollingFileTree we regularly – but not consistently – face this error:

[ERROR:flutter/runtime/dart_vm_initializer.cc(40)] Unhandled Exception: PathAccessException: Creation failed, path = '/var/mobile/Containers/Data/Application/7B8B2748-2BC0-4CA6-810B-88E170F2633B' (OS Error: Operation not permitted, errno = 1)
#0      _Directory.createSync (dart:io/directory_impl.dart:136:7)
#1      _Directory.createSync (dart:io/directory_impl.dart:131:16)
#2      _Directory.createSync (dart:io/directory_impl.dart:131:16)
#3      FimberFileTree._flushBuffer (package:fimber_io/src/file_log.dart:69:21)
#4      new FimberFileTree.<anonymous closure> (package:fimber_io/src/file_log.dart:47:13)
#5      _RootZone.runUnaryGuarded (dart:async/zone.dart:891:10)
#6      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:381:11)
#7      _BufferingStreamSubscription._add (dart:async/stream_impl.dart:312:7)

The result is that the log file cannot be created and logs are lost.

Analysis

LogFileNameFormatter, which is used by TimedRollingFileTree, is the culprit. It's responsible for formatting/replacing the date/time part of the filename. However, if any other part of the log file path matches any of the date time tokens (e.g. 'DD' for the day part), it will be replaced as well. This is especially common and uncontrollable in the application identifier.

Example

Consider an app installation with the identifier 7B8BDD48-2BC0-4CA6-810B-88E170F2633B. The filenameFormat would be something like '/var/mobile/Containers/Data/Application/7B8BDD48-2BC0-4CA6-810B-88E170F2633B/Documents/logs/log_YYYYMMDD_HHmmSS.txt'.
The statement .replaceAll(_dayToken, dateTime.day.toString().padLeft(2, '0')) in would then replace the DD in "7B8BDD48-2BC0-4CA6-810B-88E170F2633B" with 27 (on today's date), resulting in an illegal application identifier ("7B8B2748-2BC0-4CA6-810B-88E170F2633B") and the above PathAccessException.

Solution

The prefix and postfix should probably not be part of the filenameFormat and appended after replacing all the date/time tokens in the format function.

[magillus]

Hello, Thanks for bringing this up, I am not using flutter/dart for last 4 years and I do not have time to maintain this repository - feel free to clone it and do the fix on your own repository.