Problem with `isfile_casesensitive()` on Windows

[kimikage]

An internal function isfile_casesensitive() uses Win32API GetLongPathNameW on Windows.

julia/base/loading.jl

Lines 11 to 16 in 222231f

	elseif Sys.iswindows()
	# GetLongPathName Win32 function returns the case-preserved filename on NTFS.
	function isfile_casesensitive(path)
	isaccessiblefile(path) || return false # Fail fast
	basename(Filesystem.longpath(path)) == basename(path)
	end

However, the API may not be able to handle non-existent directories.

julia> dir = joinpath(DEPOT_PATH[1], "environments", "v1.10") # just an example
"C:\\Users\\username\\.julia\\environments\\v1.10"

julia> Base.Filesystem.longpath(joinpath(dir, "Project.toml"))
"C:\\Users\\username\\.julia\\environments\\v1.10\\Project.toml"

julia> Base.Filesystem.longpath(joinpath(dir, "nonexistent", "..", "Project.toml"))
ERROR: SystemError: longpath: The system cannot find the file specified.
Stacktrace:
 [1] windowserror(p::Symbol, code::UInt32; extrainfo::Nothing)
   @ Base .\error.jl:200
 [2] windowserror
   @ .\error.jl:199 [inlined]
 [3] longpath(path::String)
   @ Base.Filesystem .\path.jl:479
 [4] top-level scope
   @ REPL[3]:1

julia> versioninfo()
Julia Version 1.12.0-DEV.727
Commit 3054c00d33 (2024-06-14 05:13 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: 8 × 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
  WORD_SIZE: 64
  LLVM: libLLVM-17.0.6 (ORCJIT, tigerlake)
Threads: 1 default, 0 interactive, 1 GC (on 8 virtual cores)

This problem can also be reproduced on Julia v1.6.7.
Perhaps `normpath()' would mitigate this problem.

Incidentally, parent directories of non-existent directories seem to be invalid on Linux from the beginning.

[kimikage]

Or, (on Julia v1.11 and later)

function Base.isfile_casesensitive(path)
    Base.isaccessiblefile(path) || return false  # Fail fast
    name = basename(path)
    try
        for entry in Base.Filesystem._readdirx(dirname(path), sort = false)
            entry.name == name && return true
        end
    catch err
        isa(err, Base.IOError) || rethrow()
    end
    return false
end

[stevengj]

Why should it succeed for paths that contain non-existent directories (even if they are cancelled out by ..)?

[PallHaraldsson]

@kimikage I repeat the question above, is this a problem (change title, add "problem for nonexistent directories"?), even a bug? AND for Julia itself, since this is an internal function as you say. and longpath even more internal, where the PR "fix" is, since only available on Windows, and the "fix" not applying elsewhere...

If you were using this non-API, i.e. outside of Julia itself (if for Julia, can you then clarify what will be better for it?), then first, should it be exported, and made public, maybe at first as is? Should this issue however be closed as not a bug or "not planned" and then also the PR. I was looking into the PR, making it more general, but do not want to waste my time if this is a non-issue...

Should longpath be renamed to _longpath and/or document it only available on Windows (it's always bad to use internals, but more so in this case; the first I know of not available on all platforms)? Or alternatively a dummy implementation made for other platforms,and make it public too?