feat(NIOFileSystem): Add idempotent directory creation behavior (#3404) #3410
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glbrntt
requested changes
Oct 16, 2025
Comment on lines
807
to
825
| /// 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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Thanks for the feedback, will work on it!
glbrntt
reviewed
Oct 20, 2025
Comment on lines
852
to
853
| // Unable to determine what exists at this path. | ||
| return .failure(error) |
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In this path we should return the error from mkdir. I think it'd be a bit odd to be presented with an error from stat when mkdir failed.
glbrntt
requested changes
Oct 20, 2025
There was a problem hiding this comment.
Ah, the formatter is unhappy. It looks like you have some trailing whitespace:
--- a/Sources/NIOFS/FileSystem.swift
+++ b/Sources/NIOFS/FileSystem.swift
@@ -825,7 +825,7 @@ extension FileSystem {
break loop
case let .failure(errno):
- if errno == .fileExists {
+ if errno == .fileExists {
switch self._info(forFileAt: path, infoAboutSymbolicLink: false) {
case let .success(maybeInfo):
if let info = maybeInfo, info.type == .directory {
diff --git a/Sources/_NIOFileSystem/FileSystem.swift b/Sources/_NIOFileSystem/FileSystem.swift
index 70491ae..53174c1 100644
--- a/Sources/_NIOFileSystem/FileSystem.swift
+++ b/Sources/_NIOFileSystem/FileSystem.swift
@@ -839,7 +839,7 @@ extension FileSystem {
break loop
case let .failure(errno):
- if errno == .fileExists {
+ if errno == .fileExists {
switch self._info(forFileAt: path, infoAboutSymbolicLink: false) {
case let .success(maybeInfo):
if let info = maybeInfo, info.type == .directory {
@@ -852,7 +852,7 @@ extension FileSystem {
// Unable to determine what exists at this path.
return .failure(.mkdir(errno: errno, path: path, location: .here()))
}
- }
+ }
guard createIntermediateDirectories, errno == .noSuchFileOrDirectory else {
return .failure(.mkdir(errno: errno, path: path, location: .here()))
}
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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.