Tuesday, 22 March 2016

Elvis and King Concat

I hate LINQ's Enumerable.Concat when bringing together IEnumerables. Not the behaviour (I love that!) but rather how code ends up looking when you use it. Consider this:

var concatenated = myCollection?.Select(x => new ConcatObj(x)) ?? new ConcatObj[0].Concat(
    myOtherCollection?.Select(x => new ConcatObj(x)) ?? new ConcatObj[0]

In this example I'm bringing together 2 collections, either of which may be null (more on that later). I think we can all agree this doesn't represent a world of readability. I've also had to create a custom class ConcatObj because you can't create an empty array for an anonymous type in C#.

Attempt #1: ConcatMany

After toying around with a bunch of different ideas I created this extension method:

public static class FunctionalExtensions
    public static IEnumerable<T> ConcatMany<T>(
        this IEnumerable<T> original,
        params IEnumerable<T>[] enumerablesToConcat) => original.Concat(
            enumerablesToConcat.Where(e => e != null).SelectMany(c => c)

Thanks to the joy of params this extension allows me to bring together multiple IEnumerables into a single one but has the advantage of considerably cleaner calling code:

var concatenated = Enumerable.Empty<ConcatObj>().ConcatMany(
    myCollection?.Select(x => new ConcatObj(x)),
    myOtherCollection?.Select(x => new ConcatObj(x))

For my money this is more readable and intent is clearer. Particularly as the number of contributing IEnumerables goes up. The downside is that I can’t use anonymous objects because you need to tell the compiler what the type is when using Enumerable.Empty.

Wouldn't it be nice to have both:

  1. Readable code and
  2. Anonymous objects?

Attempt #2: EnumerableExtensions.Create

After batting round a few ideas (thanks Matt) I settled on this implementation:

public static class EnumerableExtensions
    public static IEnumerable<TSource> Create<TSource>(params IEnumerable<TSource>[] enumerables)
        return Concat(enumerables.Where(e => e != null));

    private static IEnumerable<TSource> Concat<TSource>(IEnumerable<IEnumerable<TSource>> enumerables)
        foreach (var enumerable in enumerables)
            foreach (var item in enumerable)
                yield return item;

Which allows for calling code like this:

var concatenated = EnumerableExtensions.Create(
    myCollection?.Select(x => new { Anonymous = x.Types }),
    myOtherCollection?.Select(x => new { Anonymous = x.Types })

That's right; anonymous types are back! Strictly speaking the Concat method above could be converted into a single SelectMany (and boy does ReSharper like telling me) but I'm quite happy with it as is. And to be honest, I so rarely get to use yield in my own code; I thought it might be nice to give it a whirl 😊

What Gives Elvis?

If you look closely at the implementation you'll notice that I purge all nulls when I'm bringing together the Enumerables. For why? Some may legitimately argue this is a bad idea. However, there is method in my "bad practice".

I've chosen to treat null as "not important" for this use case. I'm doing this because it emerges that ASP.NET MVC deserialises empty collections as nulls. (See here and play spot the return null;) Which is a pain. But thanks to the null purging behaviour of EnumerableExtensions.Create I can trust in the null-conditional (Elvis) operator to not do me wrong.

Thursday, 17 March 2016

Atom - Recovering from Corrupted Packages

Every now and then when I try and update my packages in Atom I find this glaring back at me:

Ug. The problem is that my atom packages have become corrupt. Quite how I couldn't say. But that's the problem. Atom, as I know from bitter experience, will not recover from this. It just sits there feeling sorry for itself. However, getting back to where you belong is simpler than you imagine:

  1. Shutdown Atom
  2. In the file system go to [Your name]/.atom (and bear in mind this is Windows; Macs / Linux may be different)
  3. You'll see an .apm folder that contains all your packages. Delete this.

When you next fire up Atom these packages will automagically come back but this time they shouldn't be corrupt. Instead you should see the happiness of normality restored:

Friday, 4 March 2016

TFS 2012 meet PowerShell, Karma and BuildNumber

To my lasting regret, TFS 2012 has no direct support for PowerShell. Such a shame as PowerShell scripts can do a lot of heavy lifting in a build process. Well, here we're going to brute force TFS 2012 into running PowerShell scripts. And along the way we'll also get Karma test results publishing into TFS 2012 as an example usage. Nice huh? Let's go!

PowerShell via csproj

It's time to hack the csproj (or whatever project file you have) again. We're going to add an AfterBuild target to the end of the file. This target will be triggered after the build completes (as the name suggests):

  <Target Name="AfterBuild">
    <Message Importance="High" Text="AfterBuild: PublishUrl = $(PublishUrl), BuildUri = $(BuildUri), Configuration = $(Configuration), ProjectDir = $(ProjectDir), TargetDir = $(TargetDir), TargetFileName = $(TargetFileName), BuildNumber = $(BuildNumber), BuildDefinitionName = $(BuildDefinitionName)" />
    <Exec Command="powershell.exe -NonInteractive -ExecutionPolicy RemoteSigned "& '$(ProjectDir)AfterBuild.ps1' '$(Configuration)' '$(ProjectDir)' '$(TargetDir)' '$(PublishUrl)' '$(BuildNumber)' '$(BuildDefinitionName)'"" />

There's 2 things happening in this target:

  1. A message is printed out during compilation which contains details of the various compile time variables. This is nothing more than a console.log statement really; it's useful for debugging and so I keep it around. You'll notice one of them is called $(BuildNumber); more on that later.
  2. A command is executed; PowerShell! This invokes PowerShell with the -NonInteractive and -ExecutionPolicy RemoteSigned flags. It passes a script to be executed called AfterBuild.ps1 that lives in the root of the project directory. To that script a number of parameters are supplied; compile time variables that we may use in the script.

Where's my BuildNumber and BuildDefinitionName?

So you've checked in your changes and kicked off a build on the server. You're picking over the log messages and you're thinking: "Where's my BuildNumber?". Well, TFS 2012 does not have that set as a variable at compile time by default. This stumped me for a while but thankfully I wasn't the only person wondering... As ever, Stack Overflow had the answer. So, deep breath, it's time to hack the TFS build template file.

Checkout the DefaultTemplate.11.1.xaml file from TFS and open it in your text editor of choice. It's find and replace time! (There are probably 2 instances that need replacement.) Perform a find for the below

[String.Format(&quot;/p:SkipInvalidConfigurations=true {0}&quot;, MSBuildArguments)]

And replace it with this:

[String.Format("/p:SkipInvalidConfigurations=true /p:BuildNumber={1} /p:BuildDefinitionName={2} {0}", MSBuildArguments, BuildDetail.BuildNumber, BuildDetail.BuildDefinition.Name)]

Pretty long line eh? Let's try breaking that up to make it more readable: (but remember in the XAML it needs to be a one liner)

    /p:BuildDefinitionName={2} {0}", MSBuildArguments, BuildDetail.BuildNumber, BuildDetail.BuildDefinition.Name)]

We're just adding 2 extra parameters of BuildNumber and BuildDefinitionName to the invocation of MSBuild. Once we've checked this back in, BuildNumber and BuildDefinitionName will be available on future builds. Yay! Important! You must have a build name that does not feature spaces; probably there's a way to pass spaces here but I'm not sure what it is.


You can use your AfterBuild.ps1 script to do any number of things. In my case I'm going to use MSTest to publish some test results which have been generated by Karma into TFS:

param ([string]$configuration, [string]$projectDir, [string]$targetDir, [string]$publishUrl, [string]$buildNumber, [string] $buildDefinitionName)

$ErrorActionPreference = 'Stop'

function PublishTestResults([string]$resultsFile) {
 Write-Host 'PublishTests'
 $mstest = 'C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\IDE\MSTest.exe'

 Write-Host "Using $mstest at $pwd"
 Write-Host "Publishing: $resultsFile"

 & $mstest /publishresultsfile:$resultsFile /publish:http://my-tfs-server:8080/tfs /teamproject:MyProject /publishbuild:$buildNumber /platform:'Any CPU' /flavor:Release

function FailBuildIfThereAreTestFailures([string]$resultsFile) {
 $results = [xml](GC $resultsFile)
 $outcome = $results.TestRun.ResultSummary.outcome
 $fgColor = if($outcome -eq "Failed") { "Red" } else { "Green" }
 $total = $results.TestRun.ResultSummary.Counters.total
 $passed = $results.TestRun.ResultSummary.Counters.passed
 $failed = $results.TestRun.ResultSummary.Counters.failed

 $failedTests = $results.TestRun.Results.UnitTestResult | Where-Object { $_.outcome -eq "Failed" }

 Write-Host Test Results: $outcome -ForegroundColor $fgColor -BackgroundColor "Black"
 Write-Host Total tests: $total
 Write-Host Passed: $passed
 Write-Host Failed: $failed

 $failedTests | % { Write-Host Failed test: $_.testName
  Write-Host $_.Output.ErrorInfo.Message
  Write-Host $_.Output.ErrorInfo.StackTrace }


 if($outcome -eq "Failed") { 
  Write-Host "Failing build as there are broken tests"

function Run() {
  Write-Host "Running AfterBuild.ps1 using Configuration: $configuration, projectDir: $projectDir, targetDir: $targetDir, publishUrl: $publishUrl, buildNumber: $buildNumber, buildDefinitionName: $buildDefinitionName"

 if($buildNumber) {
  $resultsFile = "$projectDir\test-results.trx"
  PublishTestResults $resultsFile
  FailBuildIfThereAreTestFailures $resultsFile

# Off we go...

Assuming we have a build number this script kicks off the PublishTestResults function above. So we won't attempt to publish test results when compiling in Visual Studio on our dev machine. The script looks for MSTest.exe in a certain location on disk (the default VS 2015 installation location in fact; it may be installed elsewhere on your build machine). MSTest is then invoked and passed a file called test-results.trx which is is expected to live in the root of the project. All being well, the test results will be registered with the running build and will be visible when you look at test results in TFS.

Finally in FailBuildIfThereAreTestFailures we parse the test-results.trx file (and for this I'm totally in the debt of David Robert's helpful Gist). We write out the results to the host so it'll show up in the MSBuild logs. Also, and this is crucial, if there are any failures we fail the build by exiting PowerShell with a code of 1. We are deliberately swallowing any error that Karma raises earlier when it detects failed tests. We do this because we want to publish the failed test results to TFS before we kill the build.

Bonus Karma: test-results.trx

If you've read a previous post of mine you'll be aware that it's possible to get MSBuild to kick off npm build tasks. Specifically I have MSBuild kicking off an npm run build. My package.json looks like this:

  "scripts": {
    "test": "karma start --reporters mocha,trx --single-run --browsers PhantomJS",
    "clean": "gulp delete-dist-contents",
    "watch": "gulp watch",
    "build": "gulp build",
    "postbuild": "npm run test"

You can see that the postbuild hook kicks off the test script in turn. And that test script kicks off a single run of karma. I'm not going to go over setting up Karma at all here; there are other posts out there that cover that admirably. But I wanted to share news of the karma trx reporter. This reporter is the thing that produces our test-results.trx file; trx being the format that TFS likes to deal with.

So now we've got a PowerShell hook into our build process (something very useful in itself) which we are using to publish Karma test results into TFS 2012. They said it couldn't be done. They were wrong. Huzzah!!!!!!!