Compare Powershell hash tables recursively

compare_hash_tables.ps1

# Compare Powershell hash tables using a helper function.
# Usage:
#   PS> Import-Module ./compare_hash_tables.ps1
#   PS> $hash1 = @{'1'='2'; '3'=@(@{'5'='8'; 'a'='b'},'7', 'c'); 'd'=@('e')} 
#   PS> $hash2 = @{'1'='1'; '3'=@(@{'5'='9'},'6'); 'd'=@('e','f')}
#   PS> Compare-Hashes $hash1 $hash2
#
#     : hash['3'] : list[0] : hash['5'] : <->
#       -> Expected '8'
#       -> Actually '9'
#     : hash['3'] : list[0] : hash['a'] in Expected but not Actual!
#     : hash['3'] : list[1] : <->
#       -> Expected '7'
#       -> Actually '6'
#     : hash['3'] : list['c'] in Expected but not Actual!
#     : hash['d'] : list['f'] in Actual but not Expected!
#     : hash['1'] : <->
#       -> Expected '2'
#       -> Actually '1'


function Compare-Hashes ($expected, $actual, $history='') {
    # Recursively compare hash tables.
    # Add a newline before output at recursion level 0
    if ($history -eq '') {
        Write-Host ""}
    $allKeys =  $expected.keys + $actual.keys | select -uniq
    foreach ($key in $allKeys) {
        if (($actual.keys -contains $key) -and ($expected.keys -contains $key)) {
            $history_param = $history + " : hash['$($key)']"
            Compare-NonHashes $expected[$key] $actual[$key] $history_param }
        elseif ($expected.keys -notcontains $key) {
            Write-Host "$($history) : hash['$($key)'] in Actual but not Expected!" }
        elseif ($actual.keys -notcontains $key) {
            Write-Host "$($history) : hash['$($key)'] in Expected but not Actual!" } } }

function Compare-NonHashes ($expected, $actual, $history='') {
    # Helper function for Compare-Hashes.
    if ($expected.GetType().Name -eq "HashTable") {
        Compare-Hashes $expected $actual $history }
    elseif (($expected.GetType().Name -eq "Object[]") -and ($actual.GetType().Name -eq "Object[]"))
    {
        $maxLength = $($expected.length, $actual.length | Measure -Max).Maximum
        for ($i = 0; $i -lt $maxLength; $i++) {
            if ($expected[$i] -eq $null) {
                Write-Host "$($history) : list['$($actual[$i])'] in Actual but not Expected!" }
            elseif ($actual[$i] -eq $null) {
                Write-Host "$($history) : list['$($expected[$i])'] in Expected but not Actual!" }
            else {
                $history_param = $history + " : list[$($i)]"
                Compare-NonHashes $expected[$i] $actual[$i] $history_param } } }
    else { # String
        $different = Compare-Object $expected $actual
        if ($different) {
            Write-Host "$($history) : <->"
            Write-Host "   -> Expected '$($expected)'"
            Write-Host "   -> Actually '$($actual)'" } } }