Question

I have a simple Word to Pdf converter as an MSBuild Task. The task takes Word files (ITaskItems) as input and Pdf files (ITaskItems) as output. The script uses a Target transform for conversion:

<Project DefaultTargets='Build' xmlns='http://schemas.microsoft.com/developer/msbuild/2003' ToolsVersion='3.5'>   <UsingTask AssemblyFile='$(MSBuildExtensionsPath)\MyTasks.dll' TaskName='MyTasks.DocToPdf' />   <Target Name='Build' DependsOnTargets='Convert' />   <Target Name='Convert'           Inputs='@(WordDocuments)'           Outputs='@(WordDocuments->'%(FileName).pdf')'>     <DocToPdf Inputs='@(WordDocuments)'               Outputs='%(FileName).pdf'>       <Output TaskParameter='ConvertedFiles' ItemName='PdfDocuments' />     </DocToPdf>   </Target>   <ItemGroup>     <WordDocuments Include='One.doc' />     <WordDocuments Include='SubDir\Two.doc' />      <WordDocuments Include='**\*.doc' />   </ItemGroup> </Project> 

What’s happening is that SubDir\Two.doc gets converted on every incremental build, One.doc does not (ie MSBuild correctly skips that file because it was already converted). If I use the recursive items spec (the third one above), I get the same behaviour (ie. One.doc only gets converted if the PDF is out of date or missing, but all documents in subdirectories always get converted regardless).

What am I doing wrong here?

Answer 1

I found the problem. It turns out that I had some logic in the Task that would turn any relative path specified for a PDF file into an absolute path. Once I removed that and changed the script to this:

  <Target Name='Convert'           Inputs='@(WordDocuments)'           Outputs='@(WordDocuments->'%(RelativeDir)%(FileName).pdf')'>     <DocToPdf Inputs='%(WordDocuments.Identity)'               Outputs='%(RelativeDir)%(FileName).pdf'>       <Output TaskParameter='ConvertedFiles' ItemName='PdfDocuments' />     </DocToPdf>   </Target> 

I got the behaviour I expected.