"[" and "]" characters mess up get-childitem - powershell

Question

Using PowerShell 4.0,
I am trying to get the size of multiple directories and I am getting very inconsistent results between what windows tells me and what my code is telling me.
The code in question is:
$temp4 = ($folderInfo.rootFolder).fullname
$folderInfo.directories += Get-ChildItem -LiteralPath $temp4 -Recurse -Force -Directory
$folderInfo.directories += $folderInfo.rootFolder
foreach ($dir in $folderInfo.directories)
{
$temp3 = $dir.fullname
$temp2 = Get-ChildItem -LiteralPath $temp3 -Force
$temp = (Get-ChildItem -LiteralPath $dir.fullname -Force -File | Measure-Object -Property length -Sum -ErrorAction SilentlyContinue).Sum
$folderInfo.totalSize += $temp
}
return $folderInfo
if $folderInfo.rootFolder = D:\sample
then I get what I want
but if $folderInfo.rootFolder = D:\[sample
then I get
Get-ChildItem : Cannot retrieve the dynamic parameters for the cmdlet. The specified wildcard character pattern is not valid: sample [sample
At C:\powershell scripts\test.ps1:55 char:12
+ $temp = (Get-ChildItem $dir.fullname -Force -File | Measure-Object -Property l ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidArgument: (:) [Get-ChildItem], ParameterBindingException
+ FullyQualifiedErrorId : GetDynamicParametersException,Microsoft.PowerShell.Commands.GetChildItemCommand
The same holds true if D:\sample contains a folder somewhere in it's children that is "[sample". I will get correct results from everything else, but anything in or beyond the problem directory. Both $dir.pspath and $dir.fullname screw things up.
Edit: changed the above code to reflect it's current state and included the full error.
edit again: The code above now has some debugging temp variables.

Answer 1

Use the -LiteralPath parameter in place of -Path to suppress the wildcard globbing. Also, since you're using V4, you can use the -Directory switch and dispense with the $_.iscontainer filter:
$folderInfo.directories =
Get-ChildItem -LiteralPath $folderInfo.rootFolder -Recurse -Force -Directory
If you have more squre brackets farther down the directory tree, keep using literpath in subsequent Get-ChildItem commands:
$folderInfo.directories += Get-ChildItem -LiteralPath $folderInfo.rootFolder -Recurse -Force -Directory
$folderInfo.directories += Get-Item -LiteralPath $folderInfo.rootFolder
foreach ($dir in $folderInfo.directories)
{
$temp2 = Get-ChildItem -LiteralPath $dir.PSPath -Force
$temp = (Get-ChildItem -LiteralPath $dir.fullname -Force -File | Measure-Object -Property length -Sum -ErrorAction SilentlyContinue).Sum
$folderInfo.totalSize += $temp
}
return $folderInfo