How can I get MSBUILD to evaluate and print the full path when given a relative path?

Question

How can I get MSBuild to evaluate and print in a <Message /> task an absolute path given a relative path?

Property Group

<Source_Dir>..\..\..\Public\Server\</Source_Dir>
<Program_Dir>c:\Program Files (x86)\Program\</Program_Dir>

Task

<Message Importance="low" Text="Copying '$(Source_Dir.FullPath)' to '$(Program_Dir)'" />

Output

Copying '' to 'c:\Program Files (x86)\Program\'

Answer 1

In MSBuild 4.0, the easiest way is the following:

$([System.IO.Path]::GetFullPath('$(MSBuildThisFileDirectory)\your\path'))

This method works even if the script is <Import>ed into another script; the path is relative to the file containing the above code.

(consolidated from Aaron's answer as well as the last part of Sayed's answer)

---

In MSBuild 3.5, you can use the ConvertToAbsolutePath task:

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003"
         DefaultTargets="Test"
         ToolsVersion="3.5">
  <PropertyGroup>
    <Source_Dir>..\..\..\Public\Server\</Source_Dir>
    <Program_Dir>c:\Program Files (x86)\Program\</Program_Dir>
  </PropertyGroup>

  <Target Name="Test">
    <ConvertToAbsolutePath Paths="$(Source_Dir)">
      <Output TaskParameter="AbsolutePaths" PropertyName="Source_Dir_Abs"/>
    </ConvertToAbsolutePath>
    <Message Text='Copying "$(Source_Dir_Abs)" to "$(Program_Dir)".' />
  </Target>
</Project>

Relevant output:

Project "P:\software\perforce1\main\XxxxxxXxxx\Xxxxx.proj" on node 0 (default targets).
  Copying "P:\software\Public\Server\" to "c:\Program Files (x86)\Program\".

A little long-winded if you ask me, but it works. This will be relative to the "original" project file, so if placed inside a file that gets <Import>ed, this won't be relative to that file.

---

In MSBuild 2.0, there is an approach which doesn't resolve "..". It does however behave just like an absolute path:

<PropertyGroup>
    <Source_Dir_Abs>$(MSBuildProjectDirectory)\$(Source_Dir)</Source_Dir_Abs>
</PropertyGroup>

The $(MSBuildProjectDirectory) reserved property is always the directory of the script that contains this reference.

This will also be relative to the "original" project file, so if placed inside a file that gets <Import>ed, this won't be relative to that file.

Answer 2

MSBuild 4.0 added Property Functions which allow you to call into static functions in some of the .net system dlls. A really nice thing about Property Functions is that they will evaluate out side of a target.

To evaluate a full path you can use System.IO.Path.GetFullPath when defining a property like so:

<PropertyGroup>
  <Source_Dir>$([System.IO.Path]::GetFullPath('..\..\..\Public\Server\'))</Source_Dir>
</PropertyGroup>

The syntax is a little ugly but very powerful.

Answer 3

Wayne is correct that well-known metadata does not apply to properties - only to items. Using properties such as "MSBuildProjectDirectory" will work, but I'm not aware of a built in way to resolve the full path.

Another option is to write a simple, custom task that will take a relative path and spit out the fully-resolved path. It would look something like this:

public class ResolveRelativePath : Task
{
    [Required]
    public string RelativePath { get; set; }

    [Output]
    public string FullPath { get; private set; }

    public override bool Execute()
    {
        try
        {
            DirectoryInfo dirInfo = new DirectoryInfo(RelativePath);
            FullPath = dirInfo.FullName;
        }
        catch (Exception ex)
        {
            Log.LogErrorFromException(ex);
        }
        return !Log.HasLoggedErrors;
    }
}

And your MSBuild lines would look something like:

<PropertyGroup>
    <TaskAssembly>D:\BuildTasks\Build.Tasks.dll</TaskAssembly>
    <Source_Dir>..\..\..\Public\Server\</Source_Dir>
    <Program_Dir>c:\Program Files (x86)\Program\</Program_Dir>
</PropertyGroup>
<UsingTask AssemblyFile="$(TaskAssembly)" TaskName="ResolveRelativePath" />

<Target Name="Default">
    <ResolveRelativePath RelativePath="$(Source_Dir)">
    <Output TaskParameter="FullPath" PropertyName="_FullPath" />
    </ResolveRelativePath>
    <Message Importance="low" Text="Copying '$(_FullPath)' to '$(Program_Dir)'" />
</Target>