【VBA】フォルダを作る｜MkDir（フォルダがすでに存在していればエラーになる）

' Prefer atomic create over pre-check｜事前チェックより原子的作成を優先
Public Function MakeFolderPathChain( _
		ByVal basePath As String, _
		ByVal folderName As String) As String

	' "\" を使う（ロケール非依存）｜Use "\" consistently (locale-agnostic)
	Dim folderPath As String
	folderPath = basePath & "\" & folderName

	' 親フォルダを含めて確実に作成｜Ensure parent chain exists
	Call EnsureFolderChain(folderPath)

	MakeFolderPathChain = folderPath
End Function

' Create all missing levels safely｜足りない階層を安全に作成
Private Sub EnsureFolderChain(ByVal fullPath As String)
	Dim parts() As String
	Dim i As Long
	Dim cur As String

	parts = Split(fullPath, "\")
	' ドライブレター対応（C: など）｜Handle drive prefix
	If InStr(parts(0), ":") > 0 Then
		cur = parts(0)
		i = 1
	Else
		cur = parts(0)
		i = 1
	End If

	For i = i To UBound(parts)
		If Len(cur) > 0 Then
			cur = cur & "\" & parts(i)
		Else
			cur = parts(i)
		End If

		' 事前チェック不要：作ってみて、既存エラー(75)だけ無視
		On Error Resume Next
		MkDir cur
		Select Case Err.Number
			Case 0
				' 作成成功｜Created
			Case 75
				' 既に存在｜Already exists → ignore
			Case Else
				Dim em As String
				em = "Failed to create folder: " & cur & " (Err " & Err.Number & ")"
				On Error GoTo 0
				Err.Raise vbObjectError + 513, "EnsureFolderChain", em
		End Select
		On Error GoTo 0
	Next i
End Sub

' Single-level create (simple)｜単段だけ作る簡易版
' 親が存在する前提。既存（Err 75）は握る。
Public Function MakeFolderPathSimple( _
		ByVal basePath As String, _
		ByVal folderName As String) As String

	Dim folderPath As String
	folderPath = basePath & "\" & folderName

	On Error Resume Next
	MkDir folderPath
	Select Case Err.Number
		Case 0, 75
			' 作成 or 既存 → OK
		Case Else
			Dim em As String
			em = "Failed to create: " & folderPath & " (Err " & Err.Number & ")"
			On Error GoTo 0
			Err.Raise vbObjectError + 513, "MakeFolderPathSimple", em
	End Select
	On Error GoTo 0

	MakeFolderPathSimple = folderPath
End Function