Test HttpListener so that PowerShell Core tests don't have to rely on an internet web service (#3778)

test/tools/Modules/HttpListener/HttpListener.psd1

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+@{
+ModuleVersion = '1.0.0'
+GUID = 'e148b26c-0594-4963-99e5-419d4ff302e2'
+Author = 'Steve Lee'
+CompanyName = 'Microsoft'
+Copyright = '(c) Microsoft. All rights reserved.'
+Description = 'Creates a new HTTP Listener for testing purposes'
+RootModule = 'HttpListener.psm1'
+FunctionsToExport = @('Start-HttpListener','Stop-HttpListener')
+}

test/tools/Modules/HttpListener/HttpListener.psm1

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+Function Stop-HTTPListener {
+    <#
+    .Synopsis
+        Stop HTTP Listener used for PowerShell tests rather than rely on 3rd party websites
+    .Description
+        Sends `exit` command to HTTP Listener causing it to exit.
+    .Parameter Port
+        Port to use, default is 8080
+    .Example
+        Stop-HTTPListener -Port 8080
+    #>
+    Param (
+        [Parameter()]
+        [Int] $Port = 8080
+    )
+
+    Invoke-WebRequest -Uri "http://localhost:$port/PowerShell?test=exit"
+}
+
+Function Start-HTTPListener {
+    <#
+    .Synopsis
+        Creates a new HTTP Listener to be used for PowerShell tests rather than rely on 3rd party websites
+    .Description
+        Creates a new HTTP Listener supporting several test cases intended to be used only by PowerShell tests.
+
+        Use Ctrl-C to stop the listener.  You'll need to send another web request to allow the listener to stop since
+        it will be blocked waiting for a request.
+    .Parameter Port
+        Port to listen, default is 8080
+    .Example
+        Start-HTTPListener -Port 8080
+        Invoke-WebRequest -Uri "http://localhost:8080/PowerShell/?test=linkheader&maxlinks=5"
+    #>
+    Param (
+        [Parameter()]
+        [Int] $Port = 8080,
+
+        [Parameter()]
+        [switch] $AsJob
+        )
+
+    Process {
+        $ErrorActionPreference = "Stop"
+
+        [scriptblock]$script = {
+            param ($Port)
+
+            # HttpListener.QueryString is not being populated, need to follow-up with CoreFx, workaround is to parse it ourselves
+            Function ParseQueryString([string]$url)
+            {
+                Write-Verbose "Parsing: $url"
+                $uri = [uri]$url
+                $queryItems = @{}
+                if ($uri.Query -ne $null)
+                {
+                    foreach ($segment in $uri.Query.Split("&"))
+                    {
+                        if ($segment -match "\??(?<name>\w*)(=(?<value>.*?))?$")
+                        {
+                            $name = $matches["name"]
+                            $value = $matches["value"]
+                            if ($value -ne $null)
+                            {
+                                $value = [System.Web.HttpUtility]::UrlDecode($value)
+                            }
+                            $queryItems.Add($name, $value)
+                            Write-Verbose "Found: $name = $value"
+                        }
+                    }
+                }
+                return $queryItems
+            }
+
+            $listener = [System.Net.HttpListener]::New()
+            $urlPrefix = "/PowerShell"
+            $url = "http://localhost:$Port$urlPrefix"
+            $listener.Prefixes.Add($url + "/")  # trailing slash required for registration
+            $listener.AuthenticationSchemes = [System.Net.AuthenticationSchemes]::Anonymous 
+            try {
+                Write-Warning "Note that thread is blocked waiting for a request.  After using Ctrl-C to stop listening, you need to send a valid HTTP request to stop the listener cleanly."
+                Write-Warning "Use Stop-HttpListener or Invoke-WebRequest -Uri '${Url}?test=exit' to stop the listener."
+                Write-Verbose "Listening on $Url..."
+                $listener.Start()
+                $exit = $false
+                while ($exit -eq $false) {
+                    $context = $listener.GetContext()
+                    $request = $context.Request
+                    
+                    $queryItems = ParseQueryString($request.Url)
+
+                    $test = $queryItems["test"]
+                    Write-Verbose "Testing: $test"
+
+                    # the status code to return for the response
+                    $statusCode = [System.Net.HttpStatusCode]::OK
+                    # this is the body of the response, return json/xml as appropriate
+                    $output = ""
+                    # this is hashtable of headers in the response
+                    $outputHeader = @{}
+                    # this is the contenttype, example 'application/json'
+                    $contentType = $null
+
+                    switch ($test)
+                    {
+                        $null
+                        {
+                            $statusCode = [System.Net.HttpStatusCode]::BadRequest
+                            $output = "Test not specified"
+                        }
+                        "exit"
+                        {
+                            Write-Verbose "Received command to exit listener"
+                            $output = "Exit command received"
+                            $exit = $true
+                        }
+                        "response"
+                        {
+                            $statusCode = $queryItems["statuscode"]
+                            $contentType = $queryItems["contenttype"]
+                            $output = $queryItems["output"]
+                        }
+                        "redirect"
+                        {
+                            $redirect = $queryItems["redirect"]
+                            if ($redirect -eq $null)
+                            {
+                                $statusCode = [System.Net.HttpStatusCode]::Found
+                                $redirectedUrl = "${Url}?test=redirect&redirect=false"
+                                Write-Verbose "$redirectedUrl"
+                                $outputHeader.Add("Location",$redirectedUrl)
+                                Write-Verbose "Redirecting to $($outputHeader.Location)"
+                            }
+                            else
+                            {
+                                $output = $request | ConvertTo-Json
+                            }
+                        }
+                        default
+                        {
+                            $statusCode = [System.Net.HttpStatusCode]::NotFound
+                            $output = "Unknown Test: $Test"
+                        }
+                    }
+
+                    $response = $context.Response
+                    if ($contentType -ne $null)
+                    {
+                        Write-Verbose "Setting ContentType to $contentType"
+                        $response.ContentType = $contentType
+                    }
+                    if ($statusCode -ne $null)
+                    {
+                        $response.StatusCode = $statusCode
+                    }
+                    $response.Headers.Clear()
+                    foreach ($header in $outputHeader.Keys)
+                    {
+                        $response.Headers.Add($header, $outputHeader[$header])
+                    }
+                    if ($output -ne $null)
+                    {
+                        $buffer = [System.Text.Encoding]::UTF8.GetBytes($output)
+                        $response.ContentLength64 = $buffer.Length
+                        $output = $response.OutputStream
+                        $output.Write($buffer,0,$buffer.Length)
+                        $output.Close()
+                    }
+                    $response.Close()
+                }
+            }
+            finally
+            {
+                $listener.Stop()
+            }
+        }
+
+        if ($AsJob)
+        {
+            Start-Job -ScriptBlock $script -ArgumentList $Port
+        }
+        else
+        {
+            & $script -Port $Port
+        }
+    }
+}