Using FullPath members

These rules report a call to a Path, Directory or Environment method that receives a FullPath or that has a FullPath equivalent. They are all Info rules, and all of them but MFFP0023 have a code fix.

The sections below give the details of each rule: the cases it does not report, the cases where its fix is not offered, and the differences of behavior between the original code and the fixed code.

MFFP0001: Use FullPath directly instead of Path.GetFullPath

A FullPath is already a full path: Path.GetFullPath(fullPath) returns its string unchanged. The rule also reports the overload with a base path, whose base is then ignored.

• The fix keeps the argument as written: Path.GetFullPath(fullPath.Value) becomes fullPath.Value.
• It is not offered when the result is used as the receiver of a member, such as Path.GetFullPath(fullPath).Length, or initializes a var variable: the type of the expression would change.
• Path.GetFullPath throws on the empty path; the fixed code returns it.

MFFP0002: Use the right FullPath operand directly

left / right returns right when right is a FullPath: a full path is rooted, and the / operator, like Path.Combine, ignores the left operand when the right one is rooted. The fix keeps the right operand only.

MFFP0003: Use '/' with a FullPath base instead of Path.GetFullPath

Path.GetFullPath(value, basePath) resolves value against a FullPath base: basePath / value does the same and returns a FullPath. The fix is not offered when value is a FullPath too: MFFP0001 reports that case.

MFFP0004: Use '/' operator instead of Path.Combine

The rule reports Path.Combine when any of its arguments is a FullPath, including the overloads with five arguments or more. It does not report Path.Join, which concatenates its arguments even when one of them is rooted, unlike the / operator.

• The fix starts from the last FullPath argument and appends the following arguments with /. The arguments before it are dropped: Path.Combine ignores them, because a FullPath is rooted. Path.Combine("value1", "value2", fullPath) becomes fullPath.
• It is not offered when a dropped argument may have side effects, such as a method call.
• The fixed expression is a FullPath. Where a string is required, it converts implicitly.

MFFP0005, MFFP0006, MFFP0007: name and extension

Path.GetFileName, Path.GetFileNameWithoutExtension and Path.GetExtension with a FullPath argument are replaced with the Name, NameWithoutExtension and Extension properties, which return the same strings. A complex argument is put in parentheses: Path.GetFileName(condition ? a : b) becomes (condition ? a : b).Name. See Names, extensions and parents.

MFFP0008: Use FullPath.Parent instead of Path.GetDirectoryName

• Path.GetDirectoryName returns null for a root folder; Parent returns the empty path, which converts to an empty string. Code that checks the result for null must check IsEmpty instead.
• The fix is not offered when the result is used as the receiver of a member, such as Path.GetDirectoryName(fullPath).Length, or initializes a var variable.

MFFP0009: Use FullPath.WithExtension instead of Path.ChangeExtension

fullPath.WithExtension(extension) changes the extension like Path.ChangeExtension, and returns a FullPath.

MFFP0010: Use FullPath.MakePathRelativeTo instead of Path.GetRelativePath

The rule only reports calls where both arguments are FullPath values. Note the order of the arguments: Path.GetRelativePath(relativeTo, path) becomes path.MakePathRelativeTo(relativeTo). On an empty path, MakePathRelativeTo throws an InvalidOperationException where Path.GetRelativePath throws an ArgumentException; on an empty folder, it returns the full path where Path.GetRelativePath throws.

MFFP0019: Simplify the FullPath.FromPath call

The rule reports three calls whose FromPath is redundant:

• FullPath.FromPath(fullPath) converts a FullPath to a string and back. The fix keeps the FullPath.
• FullPath.FromPath(Path.GetFullPath(path)): FromPath already resolves the path. On an empty string, Path.GetFullPath throws, while the fixed code returns the empty path.
• FullPath.FromPath(Path.Combine(...)): FullPath.Combine takes the same arguments. Path.Join is not reported.

MFFP0020: Use FullPath.FromFileSystemInfo instead of FullPath.FromPath

FullPath.FromPath(info.FullName), where info is a FileInfo, a DirectoryInfo or another FileSystemInfo, becomes FullPath.FromFileSystemInfo(info). When info is null, the original code throws a NullReferenceException, while the fixed code returns the empty path.

MFFP0022: Use FullPath.CreateParentDirectory instead of Directory.CreateDirectory

The rule reports Directory.CreateDirectory(fullPath.Parent) when its result is not used. It does not report the call when the returned DirectoryInfo is used, or with the overload that takes a UnixFileMode: CreateParentDirectory returns nothing and takes no options.

MFFP0023: Use FullPath.Parent instead of Directory.GetParent

Directory.GetParent(fullPath) returns a DirectoryInfo, where fullPath.Parent returns a FullPath. The rule has no code fix: replace the call by hand, and use FullPath where the code used the DirectoryInfo.

MFFP0024: Use the FullPath equivalent of Path.GetTempPath or Environment.GetFolderPath

The rule reports every call to Path.GetTempPath() and to both overloads of Environment.GetFolderPath. The fix calls FullPath.GetTempPath() or FullPath.GetFolderPath with the same arguments.

• Path.GetTempPath() ends with a directory separator; FullPath.GetTempPath() does not. Code that concatenates strings to the result must combine paths instead.
• For a folder that does not exist on the platform, FullPath.GetFolderPath returns the empty path, which converts to the same empty string.