adds test for optional dependencies

src/Dependency.json

@@ -0,0 +1,26 @@
+{
+    "Version": 0.1,
+    "Mandatory": {},
+    "Optional": [
+        {
+            "Name": "VMware",
+            "Modules": [
+                "VMware.VimAutomation.Core"
+            ]
+        },
+        {
+            "Name": "CiscoUCS",
+            "Modules": []
+        },
+        {
+            "Name": "FTP",
+            "Modules": [
+                "WinSCP"
+            ]
+        },
+        {
+            "Name": "NetAppFAS",
+            "Modules": []
+        }
+    ]
+}

src/Helper/Resolve-Dependency.ps1

@@ -0,0 +1,37 @@
+function Resolve-Dependency {
+    [OutputType([bool])]
+    [CmdletBinding()]
+    param (
+        [Parameter(Mandatory = $true)]
+        [string]$Name
+    )
+
+    begin {
+        $ModuleRootDir = $MyInvocation.MyCommand.Module.ModuleBase
+        $DepFilePath = Join-Path -Path $ModuleRootDir -ChildPath "Dependency.json"
+        if (Test-Path -Path $DepFilePath) {
+            $Dependency = Get-Content -Path $DepFilePath -Raw -Encoding UTF8 | ConvertFrom-Json
+        }
+        else {
+            Write-Warning ("Could not find the dependency file: {0}" -f $DepFilePath)
+        }
+        $res = @()
+    }
+
+    process {
+        $SelectedDependency = $Dependency.Optional | Where-Object {$_.Name -match $Name}
+
+        foreach ($Module in $SelectedDependency.Modules) {
+            $res += Test-Module -Name $Module
+        }
+        if ($res -contains $false) {
+            return $false
+        }
+        else {
+            return $true
+        }
+    }
+
+    end {
+    }
+}

src/Helper/Test-Module.ps1

@@ -0,0 +1,105 @@
+function Test-Module {
+    <#
+    .SYNOPSIS
+        Internal helper to check optional dependencies.
+
+    .DESCRIPTION
+        Test-Dependency checks if the given module or pssnapin is available on the system. It returns a bool value
+        So it is possible to use this function in a if condition.
+
+    .PARAMETER Name
+        Define a item name you need to test
+
+    .PARAMETER Type
+        Define the dependency type. This could be a Module or PSnapin.
+
+    .PARAMETER MessagePattern
+        You an optionally adjust the message pattern for the error message itself.
+        The available placeholders are:
+        - {0} : Type
+        - {1} : Name
+
+    .PARAMETER StopIfFails
+        This switch forces the entire script to stop if the given dependency object fails.
+
+    .INPUTS
+        [None]
+
+    .OUTPUTS
+        [Bool]
+
+    .EXAMPLE
+        .\Test-Dependency -Name 'VMware.PowerCLI' -Type 'Module'
+
+    .EXAMPLE
+        .\Test-Dependency -Name 'VMware.PowerCLI' -Type 'Module' -StopIfFails
+
+    .NOTES
+        File Name   : Get-RandomKey.ps1
+        Author      : Marco Blessing - marco.blessing@googlemail.com
+        Requires    :
+
+    .LINK
+        https://github.com/OCram85/PSCredentialStore
+    #>
+    [OutputType([bool])]
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory = $true)]
+        [ValidateNotNullOrEmpty()]
+        [string]$Name,
+
+        [Parameter(Mandatory = $false)]
+        [ValidateSet('Module', 'PSSnapin', 'Custom')]
+        [string]$Type = 'Module',
+
+        [Parameter(Mandatory = $false)]
+        [ValidateNotNullOrEmpty()]
+        [string]$MessagePattern = @"
+Could not find the required {0} called {1}. Please install the required {0} to run this function!
+"@,
+        [Parameter(Mandatory = $false)]
+        [switch]$StopIfFails
+    )
+    begin {
+
+    }
+
+    process {
+        $Message = $MessagePattern -f $Type, $Name
+        Write-Debug $Message
+        switch ($Type) {
+            'Module' {
+                if (Get-Module -Name $Name -ListAvailable) {
+                    return $true
+                }
+                else {
+                    if ($StopIfFails) {
+                        Write-Error -Message $Message -ErrorAction Stop -Category NotInstalled
+                    }
+                    return $false
+                }
+            }
+
+            'PSSnapin' {
+                if (Get-PSSnapin -Name $Name -Registered) {
+                    return $true
+                }
+                else {
+                    if ($StopIfFails) {
+                        Write-Error -Message $Message -ErrorAction Stop -Category NotInstalled
+                        return $false
+                    }
+                }
+            }
+
+            'Custom' {
+                Throw 'Custom tests are not implemented yet!'
+            }
+        }
+    }
+
+    end {
+
+    }
+}