Use Exec-Process

The `&` operator in Powershell does not easily allow arguments to be
conditionally emitted into a command. This is because instead of
inserting string contents when using variable replacement it will insert
a quoted string instead. Using `Exec-Process` instead as it does proper
substitution

build/scripts/build-utils.ps1

@@ -27,36 +27,70 @@ function Exec-Block([scriptblock]$cmd) {
     } 
 }
 
-function Exec-CommandCore([string]$command, [string]$commandArgs, [switch]$useConsole = $true) {
+# This will exec a process using the console and return it's exit code. This will not 
+# throw when the process fails.
+function Exec-Process([string]$command, [string]$commandArgs) {
     $startInfo = New-Object System.Diagnostics.ProcessStartInfo
     $startInfo.FileName = $command
     $startInfo.Arguments = $commandArgs
-
     $startInfo.UseShellExecute = $false
     $startInfo.WorkingDirectory = Get-Location
 
-    if (-not $useConsole) {
-       $startInfo.RedirectStandardOutput = $true
-       $startInfo.CreateNoWindow = $true
+    $process = New-Object System.Diagnostics.Process
+    $process.StartInfo = $startInfo
+    $process.Start() | Out-Null
+
+    $finished = $false
+    try {
+        while (-not $process.WaitForExit(100)) { 
+            # Non-blocking loop done to allow ctr-c interrupts
+        }
+
+        $finished = $true
+        $process.ExitCode
+    }
+    finally {
+        # If we didn't finish then an error occured or the user hit ctrl-c.  Either
+        # way kill the process
+        if (-not $finished) {
+            $process.Kill()
+        }
+    }
+}
+
+function Exec-CommandCore([string]$command, [string]$commandArgs, [switch]$useConsole = $true) {
+    if ($useConsole) {
+        $exitCode = Exec-Process $command $commandArgs
+        if ($exitCode -ne 0) { 
+            throw "Command failed to execute with exit code $($process.ExitCode): $command $commandArgs" 
+        }
+        return
     }
 
+    $startInfo = New-Object System.Diagnostics.ProcessStartInfo
+    $startInfo.FileName = $command
+    $startInfo.Arguments = $commandArgs
+
+    $startInfo.UseShellExecute = $false
+    $startInfo.WorkingDirectory = Get-Location
+    $startInfo.RedirectStandardOutput = $true
+    $startInfo.CreateNoWindow = $true
+
     $process = New-Object System.Diagnostics.Process
     $process.StartInfo = $startInfo
     $process.Start() | Out-Null
 
     $finished = $false
     try {
-        if (-not $useConsole) { 
-            # The OutputDataReceived event doesn't fire as events are sent by the 
-            # process in powershell.  Possibly due to subtlties of how Powershell
-            # manages the thread pool that I'm not aware of.  Using blocking
-            # reading here as an alternative which is fine since this blocks 
-            # on completion already.
-            $out = $process.StandardOutput
-            while (-not $out.EndOfStream) {
-                $line = $out.ReadLine()
-                Write-Output $line
-            }
+        # The OutputDataReceived event doesn't fire as events are sent by the 
+        # process in powershell.  Possibly due to subtlties of how Powershell
+        # manages the thread pool that I'm not aware of.  Using blocking
+        # reading here as an alternative which is fine since this blocks 
+        # on completion already.
+        $out = $process.StandardOutput
+        while (-not $out.EndOfStream) {
+            $line = $out.ReadLine()
+            Write-Output $line
         }
 
         while (-not $process.WaitForExit(100)) { 
@@ -65,7 +99,7 @@ function Exec-CommandCore([string]$command, [string]$commandArgs, [switch]$useCo
 
         $finished = $true
         if ($process.ExitCode -ne 0) { 
-            throw "Command failed to execute: $command $commandArgs" 
+            throw "Command failed to execute with exit code $($process.ExitCode): $command $commandArgs" 
         }
     }
     finally {

build/scripts/vsts-robocopy.ps1

@@ -3,116 +3,55 @@
 [CmdletBinding()]
 param(
     [Parameter(Mandatory = $true)]
-    [string]$Source,
+    [string]$source,
 
     [Parameter(Mandatory = $true)]
-    [string]$Target,
+    [string]$target,
 
     [Parameter(Mandatory = $true)]
-    [int]$ParallelCount,
+    [int]$parallelCount,
 
     [Parameter(Mandatory = $false)]
-    [string]$File,
+    [string]$file,
     
     [Parameter(Mandatory = $false)]
-    [string[]]$Exclude)
-
-# This script translates the output from robocopy into UTF8. Node has limited
-# built-in support for encodings.
-#
-# Robocopy uses the system default code page. The system default code page varies
-# depending on the locale configuration. On an en-US box, the system default code
-# page is Windows-1252.
-#
-# Note, on a typical en-US box, testing with the '' character is a good way to
-# determine whether data is passed correctly between processes. This is because
-# the '' character has a different code point across each of the common encodings
-# on a typical en-US box, i.e.
-#   1) the default console-output code page (IBM437)
-#   2) the system default code page (i.e. CP_ACP) (Windows-1252)
-#   3) UTF8
+    [string[]]$exclude)
 
 $ErrorActionPreference = 'Stop'
+Set-StrictMode -version 2.0
 
-# Redefine the wrapper over STDOUT to use UTF8. Node expects UTF8 by default.
-$stdout = [System.Console]::OpenStandardOutput()
-$utf8 = New-Object System.Text.UTF8Encoding($false) # do not emit BOM
-$writer = New-Object System.IO.StreamWriter($stdout, $utf8)
-[System.Console]::SetOut($writer)
-
-# All subsequent output must be written using [System.Console]::WriteLine(). In
-# PowerShell 4, Write-Host and Out-Default do not consider the updated stream writer.
+try {
+    . (Join-Path $PSScriptRoot "build-utils.ps1")
 
-if (!$File) {
-    $File = "*";
-}
-
-# Print the ##command. The /MT parameter is only supported on 2008 R2 and higher.
-if ($ParallelCount -gt 1) {
-    [System.Console]::WriteLine("##[command]robocopy.exe /E /COPY:DA /NP /R:3 /MT:$ParallelCount `"$Source`" `"$Target`" `"$File`"")
-}
-else {
-    [System.Console]::WriteLine("##[command]robocopy.exe /E /COPY:DA /NP /R:3 `"$Source`" `"$Target`" `"$File`"")
-}
-
-# The $OutputEncoding variable instructs PowerShell how to interpret the output
-# from the external command.
-$OutputEncoding = [System.Text.Encoding]::Default
+    if (!$File) {
+        $File = "*";
+    }
 
-$ExcludeArg = ""
-if (($null -ne $Exclude) -and ($Exclude.Length -gt 0)) {
-    $ExcludeArg = "/XD "
-    foreach ($e in $Exclude) {
-        $ExcludeArg += "$e "
+    $commandLine = "/E /COPY:DA /NP /R:3 "
+    if ($parallelCount -gt 1) {
+        $commandLine += "/MT:$parallelCount "
     }
-}
 
-#             Usage :: ROBOCOPY source destination [file [file]...] [options]
-#            source :: Source Directory (drive:\path or \\server\share\path).
-#       destination :: Destination Dir  (drive:\path or \\server\share\path).
-#              file :: File(s) to copy  (names/wildcards: default is "*.*").
-#                /E :: copy subdirectories, including Empty ones.
-# /COPY:copyflag[s] :: what to COPY for files (default is /COPY:DAT).
-#                      (copyflags : D=Data, A=Attributes, T=Timestamps).
-#                      (S=Security=NTFS ACLs, O=Owner info, U=aUditing info).
-#               /NP :: No Progress - don't display percentage copied.
-#			/MT[:n] :: Do multi-threaded copies with n threads (default 8).
-#                       n must be at least 1 and not greater than 128.
-#                       This option is incompatible with the /IPG and /EFSRAW options.
-#                      Redirect output using /LOG option for better performance.
-#              /R:n :: number of Retries on failed copies: default 1 million.
-#
-# Note, the output from robocopy needs to be iterated over. Otherwise PowerShell.exe
-# will launch the external command in such a way that it inherits the streams.
-#
-# Note, the /MT parameter is only supported on 2008 R2 and higher.
-if ($ParallelCount -gt 1) {
-    & robocopy.exe /E /COPY:DA /NP /R:3 /MT:$ParallelCount $Source $Target $File $ExcludeArg 2>&1 |
-        ForEach-Object {
-        if ($_ -is [System.Management.Automation.ErrorRecord]) {
-            [System.Console]::WriteLine($_.Exception.Message)
-        }
-        else {
-            [System.Console]::WriteLine($_)
+    $commandLine += "$source $target $file "
+
+    if (($null -ne $exclude) -and ($exclude.Length -gt 0)) {
+        $commandLine += "/XD "
+        foreach ($e in $exclude) {
+            $commandLine += "$e "
         }
     }
-}
-else {
-    & robocopy.exe /E /COPY:DA /NP /R:3 $Source $Target $File $ExcludeArg 2>&1 |
-        ForEach-Object {
-        if ($_ -is [System.Management.Automation.ErrorRecord]) {
-            [System.Console]::WriteLine($_.Exception.Message)
-        }
-        else {
-            [System.Console]::WriteLine($_)
-        }
+
+    Write-Host "robocopy $commandLine"
+    $exitCode = Exec-Process "robocopy" $commandLine
+    if ($exitCode -gt 8) {
+        Write-Host "robocopy failed $exitCode"
     }
-}
 
-[System.Console]::WriteLine("##[debug]robocopy exit code '$LASTEXITCODE'")
-[System.Console]::Out.Flush()
-if ($LASTEXITCODE -ge 8) {
-    exit $LASTEXITCODE
+    exit 0
+}
+catch {
+    Write-Host $_
+    Write-Host $_.Exception
+    Write-Host $_.ScriptStackTrace
+    exit 1
 }
-
-exit 0

docs/contributing/Powershell Guidelines.md

@@ -113,3 +113,16 @@ Invoke-Expression "& $command $args"
 Exec-Command $command $args
 ```
 
+## Comarisons with null
+Whenever comparing with `$null` always make sure to put `$null` on the left hand side of the 
+operator. For non-collection types this doesn't really affect behavior. For collection types though
+having a collection on the left hand side changes the meaning of `-ne` and `-eq`. Instead of checking
+for `$null` it will instead compare collection contents.
+
+``` powershell
+# DO NOT
+if ($e -ne $null) { ... }
+# DO
+if ($null -ne $e) { ... }
+```
+