👨‍💻 Improves Parameter Validation for Set-ItemNixMode

src/ConvertTo-NixMode.ps1

@@ -0,0 +1,58 @@
+#!/usr/bin/env pwsh
+$ErrorActionPreference = "Stop"
+Set-StrictMode -Version Latest
+
+
+<#
+.SYNOPSIS
+    Converts a value to a strongly-typed [System.IO.UnixFileMode] enum value.
+.DESCRIPTION
+    Converts a value to a strongly-typed [System.IO.UnixFileMode] enum value.
+.EXAMPLE
+    ConvertTo-NixMode -FromOctal 755
+#>
+function ConvertTo-NixMode() {
+    [CmdletBinding()]
+    [OutputType([System.IO.UnixFileMode])]
+    param(
+        [Parameter(Mandatory = $true, Position = 0, ParameterSetName = 'FromOctal')]
+        [ValidateNotNullOrEmpty()]
+        [string] $FromOctal,
+
+        [Parameter(Mandatory = $true, Position = 0, ParameterSetName = 'FromDecimal')]
+        [ValidateNotNullOrEmpty()]
+        [int] $FromDecimal
+    )
+    Begin {
+        function Factor-EnumValue() {
+            [OutputType([System.IO.UnixFileMode])]
+            param(
+                [Parameter(Mandatory = $true)]
+                [int]
+                $Value
+            )
+            $value = [int]$Value
+            $result = [System.IO.UnixFileMode]::None
+
+            foreach ($enumValue in [System.Enum]::GetValues([System.IO.UnixFileMode])) {
+                if (($value -band $enumValue) -eq $enumValue) {
+                    $result = $result -bor $enumValue
+                    $value = $value -bxor $enumValue
+                }
+            }
+
+            if ($value -ne 0) {
+                throw [System.ArgumentException]::new("Unable to interpret value '$FromDecimal' as a value of [System.IO.UnixFileMode].")
+            } else {
+                return $result
+            }
+        }
+
+        if ($FromOctal) {
+            $FromDecimal = [Convert]::ToInt32($FromOctal, 8)
+        }
+    }
+    Process {
+        return (Factor-EnumValue $FromDecimal)
+    }
+}

src/Set-ItemNixMode.ps1

@@ -9,12 +9,12 @@ if ($IsLinux) {
             [Parameter(Mandatory = $true)]
             [string[]]
             $Path,
+
             [Parameter(Mandatory = $true)]
-            [System.IO.UnixFileMode]
-            $Mode
+            [ValidateScript({ ConvertTo-NixMode -FromOctal $_ })]
+            [string] $ModeOctal
         )
-        [string] $modeInOctal = [Convert]::ToString([int]$Mode, 8)
-        Get-Item $Path | ForEach-Object { chmod $modeInOctal $_.FullName } | Out-Null
+        Get-Item $Path | ForEach-Object { chmod $ModeOctal $_.FullName } | Out-Null
     }
 } else {
     function Set-ItemNixMode() {

test/ConvertTo-NixMode.Tests.ps1

@@ -0,0 +1,81 @@
+#!/usr/bin/env pwsh
+#Requires -Modules "Pester"
+$ErrorActionPreference = "Stop"
+Set-StrictMode -Version Latest
+
+
+BeforeAll {
+    $SutFile = Get-Item "$PSScriptRoot/../src/ConvertTo-NixMode.ps1"
+    $SutName = $SutFile.BaseName
+}
+
+Describe "SUT file" {
+    It "should exist" {
+        $SutFile | Should -Exist
+    }
+
+    It "should be sourceable" {
+        { . $SutFile.FullName } | Should -Not -Throw
+    }
+
+    Context "when sourced" {
+        BeforeEach {
+            . $SutFile
+        }
+
+        Describe "function" {
+            It "should be defined" {
+                Get-Command -Name $SutName -CommandType Function | Should -Not -BeNullOrEmpty
+            }
+
+            Context "when invoked" {
+                Context "with no arguments" {
+                    It "should throw" {
+                        { & $SutName } | Should -Throw
+                    }
+                }
+
+                Context "via parameter" {
+                    # single integer matching a UnixFileMode value
+                    Context "single input is integer-equivalent [System.IO.UnixFileMode] value" {
+                        It "should return the value as-is" {
+                            $parameterValue = [int][Convert]::ToString([int][System.IO.UnixFileMode]::GroupExecute, 8)
+                            $expectedResult = [System.IO.UnixFileMode]::GroupExecute
+
+                            $actualResult = ConvertTo-NixMode -FromOctal $parameterValue
+
+                            $actualResult | Should -BeOfType [System.IO.UnixFileMode]
+                            $actualResult | Should -Be $expectedResult
+                        }
+                    }
+
+                    # single integer that should have been parsed as base8
+                    Context "single input is integer wrongly parsed as base10 instead of base8" {
+                        It "should return the value converted" {
+                            $parameterValue = [int]700
+                            $expectedResult = [System.IO.UnixFileMode]([Convert]::ToInt32('700', 8))
+
+                            $actualResult = ConvertTo-NixMode -FromOctal $parameterValue
+
+                            $actualResult | Should -BeOfType [System.IO.UnixFileMode]
+                            $actualResult | Should -Be $expectedResult
+                        }
+                    }
+
+                    # single integer string matching a UnixFileMode value as-is
+                    Context "single input is an integer string matching a [System.IO.UnixFileMode] value as-is" {
+                        It "should return the value as-is" {
+                            $parameterValue = [Convert]::ToString([int][System.IO.UnixFileMode]::GroupExecute, 8)
+                            $expectedResult = [System.IO.UnixFileMode]::GroupExecute
+
+                            $actualResult = ConvertTo-NixMode -FromOctal $parameterValue
+
+                            $actualResult | Should -BeOfType [System.IO.UnixFileMode]
+                            $actualResult | Should -Be $expectedResult
+                        }
+                    }
+                }
+            }
+        }
+    }
+}