Question

I’m trying to combine all javascript files in a project during the build process, but it just isn’t working for me. Here’s what I have:

<Target Name="CombineJS">
  <CreateItem Include=".\**\*.js">
    <Output TaskParameter="Include" ItemName="jsFilesToCombine" />
  </CreateItem>

  <ReadLinesFromFile File="@(jsFilesToCombine)">
    <Output TaskParameter="Lines" ItemName="jsLines" />
  </ReadLinesFromFile>

  <WriteLinesToFile File="all.js" Lines="@(jsLines)" Overwrite="true" />
</Target>

MSBuild is throwing an error on the ReadLinesFromFile line saying there’s an invalid value for the “File” parameter. (No error when there’s only one file to combine)

So, two questions:

1. What am I doing wrong?
2. Is there a better way to combine files within an MSBuild task? I ask this question because I know that my current process removes all tabs and blank lines, which for me isn’t that big of a deal, but still kind of annoying.

Answer 1

Change line 6 to:

<ReadLinesFromFile File="%(jsFilesToCombine.FullPath)">

The @ operator is used when the input is ItemGroup which is essentially a semicolon-delimited list of strings.

The % operator is for expanding ItemGroups into strings (properties).