MSBuild – Access to the path is denied

The problem:

I was configuring a new build on Bamboo CI server for a ASP.NET application. The solution built locally just fine, but consistently failed on the build server. This was the error:

(BeforeBuild target) -> 
  C:\Bamboo\src\MC-BUILD-JOB1\MyProject.Web\MyProject.Web.csproj(1851,5):
 error : Could not write Destination file: 
Access to the path 'C:\Bamboo\src\MC-BUILD-JOB1\MyProject.Web\Config\AppSettings.config' is denied.

The problem was in the following line:

<TransformXml Source="Config\AppSettings.Base.config" 
              Transform="Config\AppSettings.$(Configuration).config" 
              Destination="Config\AppSettings.config" />

So basically the TransformXml task was failing because the file Config\AppSettings.config was checked out as read-only in the build server.

Fortunately there is an easy workaround. The trick is to apply the XML transformations to a temp file and then use the Copy task with the OverwriteReadOnlyFiles attribute set to “True” to overwrite the file Config\AppSettings.config:

<TransformXml Source="Config\AppSettings.Base.config" 
              Transform="Config\AppSettings.$(Configuration).config" 
              Destination="Config\AppSettings_temp.config" />
<Copy SourceFiles="Config\AppSettings_temp.config" 
      DestinationFiles="Config\AppSettings.config" 
      OverwriteReadOnlyFiles="True" />
<Delete Files="Config\AppSettings_temp.config" />

Powershell scripts running on Bamboo don’t return the correct exit code

As part of an deployment project on Bamboo CI, I was running a powershell script to deploy an ASP.NET application to a Cloud Service on Azure.

Even though there was an error executing the script, Bamboo was setting the status of the Deployment to Success. Why? Because the exit code returned by the powershell script is always 0 (zero means successful execution).

After some research I was able to find a way to return the correct exit code in case of failure. I added the following lines to the top of my powershell script:

trap
{
    write-output $_
    exit 1
}

The trap statement includes a list of statements to run when a terminating error occurs – in this case, every time an error occurs the error message will be displayed and then the script will return a correct exit code indicating a failure. I am returning 1 but any value different from 0 (zero) will do the trick 🙂