How do I do a MSBuild Condition testing if an ItemGroup contains an item?

Question

This should be simple, but I can't find how to do this (or maybe it's not possible).

In MSBuild I have an ItemGroup that is a list of files. I want to execute a task only if a particular file is in that ItemGroup

Something like:

<Copy Condition="@(Files) <contains> C:\MyFile.txt" .... />

Any way to do this? Preferably without writing a custom task.

Edit: The list of files is only to do with the condition. Otherwise it has no relation to the task.

Humid

Answer 1

Try

<Copy Condition="'%(Files.Identity)' == 'C:\MyFile.txt'" .. />

Lillielilliputian

Yes, this should work. % will make it "iterate" thru all Files existing... is equivalent to: <Copy Condition="'$(File1.Identity)' == 'C:\MyFile.txt'" .. /> <Copy Condition="'$(File2.Identity)' == 'C:\MyFile.txt'" .. /> <Copy Condition="'$(File3.Identity)' == 'C:\MyFile.txt'" .. /> etc... – Imperator

Maybe I've misunderstood this, but I actually only want to execute the copy once, and what I'm copying is not in the list of files, it's something different. The list of files is only for the condition – Humid

It will iterate through the multiple batches, but the Copy task will be executed only once, when the condition is true. @(Files) doesn't need to be the set of files that you are copying, we are using it here only to ensure that we execute this Copy task only if "C:\MyFile.txt" is present in @(Files). – Lillielilliputian

Too bad this only works in an actual task and not at every possible "Condition" attribute. – Ashore

This works to execute one task per matching item, but what do you do if you want to do e.g. execute only if ALL or NONE match? – Trefler

@TimLovell-Smith No, I believe the example shown does not execute "one [<Copy...>] per matching item" but rather executes the <Copy...> task either once or not at all (using other operational parameters that are not shown here), based on whether "a particular file is [mentioned]" in the ItemGroup, which is just what the OP requested. The situation you want is a bit weird (matching both of either all or none, but not in-between) so I'd start thinking about a more elaborate <Choose> <When .../> <Otherwise .../> </Choose> construct... – Endorse

@Glenn Slayden by 'per matching item' IIRC I meant 'a particular file is [mentioned]"' in the sense that usually there's only one matching item... however what if the item group contains duplicates? – Trefler

Answer 2

I had a similar issue, where I wanted to do something if a file was not included in an itemGroup. In my case, it was the <Compile> item group.

This snippet is scanning through all the files in the tag, and for each one, if the file's FullPath matches the TheFileIAmLookingFor, then I set a property indicating the file was found.

Then I can use that property, and if it isn't set, I can assume the item wasn't included in the <Compile> item group. In my case, the final action is to add the item only if it didn't exist. For context, I came across this issue while working on code-generation via custom msbuild build tasks, and the generated code was sometimes getting referenced twice, which was throwing a warning.

  <Target Name="CheckForFile" BeforeTargets="CoreCompile"">
    <PropertyGroup>
        <DoesMyFileExist Condition="%(Compile.FullPath) == $(TheFileIAmLookingFor)">1</DoesMyFileExist>
    </PropertyGroup>

    <Message Importance="high" Condition="$(DoesMyFileExist)=='1'" Text="It exists"/>
    <Message Importance="high" Condition="$(DoesMyFileExist)!='1'" Text="It does not exist!"/>
    
    <ItemGroup Condition="$(DoesMyFileExist)!='1'">
      <Compile Include="$(TheFileIAmLookingFor)" />
    </ItemGroup>
  </Target>

Oys