EnvPaths.psm1

function Add-EnvPath {
    param(
        [Parameter(Mandatory=$true)]
        [string] $Path,

        [ValidateSet('Machine', 'User', 'Session')]
        [string] $Container = 'Session'
    )

    if ($Container -ne 'Session') {
        $containerMapping = @{
            Machine = [EnvironmentVariableTarget]::Machine
            User = [EnvironmentVariableTarget]::User
        }
        $containerType = $containerMapping[$Container]

        $persistedPaths = [Environment]::GetEnvironmentVariable('Path', $containerType) -split ';'
        if ($persistedPaths -notcontains $Path) {
            $persistedPaths = $persistedPaths + $Path | where { $_ }
            [Environment]::SetEnvironmentVariable('Path', $persistedPaths -join ';', $containerType)
        }
    }

    $envPaths = $env:Path -split ';'
    if ($envPaths -notcontains $Path) {
        $envPaths = $envPaths + $Path | where { $_ }
        $env:Path = $envPaths -join ';'
    }
}

function Remove-EnvPath {
    param(
        [Parameter(Mandatory=$true)]
        [string] $Path,

        [ValidateSet('Machine', 'User', 'Session')]
        [string] $Container = 'Session'
    )

    if ($Container -ne 'Session') {
        $containerMapping = @{
            Machine = [EnvironmentVariableTarget]::Machine
            User = [EnvironmentVariableTarget]::User
        }
        $containerType = $containerMapping[$Container]

        $persistedPaths = [Environment]::GetEnvironmentVariable('Path', $containerType) -split ';'
        if ($persistedPaths -contains $Path) {
            $persistedPaths = $persistedPaths | where { $_ -and $_ -ne $Path }
            [Environment]::SetEnvironmentVariable('Path', $persistedPaths -join ';', $containerType)
        }
    }

    $envPaths = $env:Path -split ';'
    if ($envPaths -contains $Path) {
        $envPaths = $envPaths | where { $_ -and $_ -ne $Path }
        $env:Path = $envPaths -join ';'
    }
}

function Get-EnvPath {
    param(
        [Parameter(Mandatory=$true)]
        [ValidateSet('Machine', 'User')]
        [string] $Container
    )

    $containerMapping = @{
        Machine = [EnvironmentVariableTarget]::Machine
        User = [EnvironmentVariableTarget]::User
    }
    $containerType = $containerMapping[$Container]

    [Environment]::GetEnvironmentVariable('Path', $containerType) -split ';' |
        where { $_ }
}

Export-ModuleMember -Function *

@mkropat Can you please tell me what is the benefit of this filtering | where { $_ } ?
Wouldn't the result be exactly the same without this?

@mkropat Can you please tell me what is the benefit of this filtering | where { $_ } ?
Wouldn't the result be exactly the same without this?

It filters out any records that is regarded as "falsy" values, including empty and null values.

Recommended change to Get-EnvPath:

function Get-EnvPath {
    param(
        [Parameter(Mandatory=$true)]
        [ValidateSet('Machine', 'User', 'Session')]
        [string] $Container
    )

    $containerMapping = @{
        Machine = [EnvironmentVariableTarget]::Machine
        User = [EnvironmentVariableTarget]::User
    }
    $containerType = $containerMapping[$Container]

    switch( $Container ){
        "Session" {
            $env:Path -split ";" |
                where { $_ }
        }
        default {
            [Environment]::GetEnvironmentVariable('Path', $containerType) -split ';' |
                where { $_ }
        }
    }
}

instead of hardcode ";"
Would you mind replacing it with [IO.Path]::PathSeparator?