feat(NIOFileSystem): Add idempotent directory creation behavior (#3404) #3410
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glbrntt
requested changes
Oct 16, 2025
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| /// Handle _createDirectory failure if the directory already exists. | ||
| private func _handleCreateDirectoryFileExists( | ||
| at path: FilePath, | ||
| ) -> Result<Void, FileSystemError> { | ||
| // This function is called when _createDirectory fails with (errno = .fileExists), | ||
| // - If the path exists and is a directory, if so return success. | ||
| // - If the path exists and is not a directory, return failure. | ||
| switch Syscall.stat(path: path) { | ||
| case .success(let stat): | ||
| // Check if it's a directory | ||
| if (stat.st_mode & S_IFMT) == S_IFDIR { | ||
| return .success(()) | ||
| } else { | ||
| return .failure(.mkdir(errno: .fileExists, path: path, location: .here())) | ||
| } | ||
| case let .failure(errno): | ||
| return .failure(.mkdir(errno: errno, path: path, location: .here())) | ||
| } | ||
| } |
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I don't think we need a whole new function for this, we already have the _info function which does most of this for you.
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| if errno == .fileExists { | ||
| return self._handleCreateDirectoryFileExists(at: path) | ||
| } |
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This isn't necessary: we're creating child directories here which we'll only do if it didn't already exist.
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The createDirectory function will succeed without error if the target directory already exists.
Motivation
This change addresses issue #3404. Currently,
fileSystem.createDirectoryfails if the target directory already exists, forcing users to write boilerplate try/catch blocks to handle this common and expected case.The goal is to make this function's behavior idempotent.
Modifications
To achieve this, I've made the following changes:
(Implementation) A new private helper function,
_handleCreateDirectoryFileExists, was introduced. This function is responsible for:statcall on the path that failed.S_IFDIR)..fileExistserror if it's a file or another type of entity.(Logic) The core
_createDirectoryfunction was updated to call this new helper function wheneverSyscall.mkdirfails with anEEXIST(.fileExists) error. This check is applied in both internal loops to correctly handle cases where either an intermediate directory or the final target directory already exists.Result
With this change, users can now call the function
fileSystem.createDirectoryand the operation will succeed even if the directory is already present, leading to cleaner and more predictable code.