How do I selectively perform certain responses tasks or targets based on item properties

[mwpowellhtx]

Let's say we have:

<ItemGroup>
  <MySpec Include="Alpha" Type="Module" ... />
  <MySpec Include="Bravo" Type="Feature" ... />
  <MySpec Include="Charlie" Type="Feature" ... />
  <MySpec Include="Delta" Type="Theme" ... />
  <MySpec Include="Echo" Type="Theme" ... />
  <MySpec Include="Foxtrot" Type="SomethingElse" ... />
</ItemGroup>

My goal there, if possible, is to filter on all Module, Feature, Theme, then anything else with the Type as such. Is it possible?

And while it would be 'simple enough' to add specialized item lists, I would like to avoid that if at all possible, and simply support a single variant style shape.

I think that the solution must probably involve some sort of copying from one source items list to another, using a condition, predicate, or what have you, but the tasks, inputs, outputs, etc, are a bit unfamiliar to me.

[mwpowellhtx]

For instance, FindInList seems like a possible application here, but would be fantastic to have some examples. i.e. given the source list items, find what/how, directed to what targets, and so forth.

[jrdodds]

It sounds like you are asking about how to do batching.

Here is an example of task batching using your example data:

<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
    <ItemGroup>
        <MySpec Include="Alpha" Type="Module" />
        <MySpec Include="Bravo" Type="Feature" />
        <MySpec Include="Charlie" Type="Feature" />
        <MySpec Include="Delta" Type="Theme" />
        <MySpec Include="Echo">
            <Type>Theme</Type>
        </MySpec>
        <MySpec Include="Foxtrot" Type="SomethingElse" />
    </ItemGroup>

    <Target Name="Test">
        <Message Text="Features:     @(MySpec, ', ')" Condition="%(Type) == 'Feature'"/>
        <Message Text="Modules:      @(MySpec, ', ')" Condition="%(Type) == 'Module'"/>
        <Message Text="Misc:         @(MySpec, ', ')" Condition="%(Type) == 'Misc'"/>
        <Message Text="Themes+Other: @(MySpec, ', ')" Condition="%(Type) != 'Feature' and %(Type) != 'Module'"/>

        <ItemGroup>
            <SubSet Include="@(MySpec)" Condition="%(MySpec.Type) != 'Feature' and %(MySpec.Type) != 'Module'" />
        </ItemGroup>
        <Message Text="Subset:       @(Subset, ', ')" />
    </Target>
</Project>

The output will be:

         Features:     Bravo, Charlie
         Modules:      Alpha
         Themes+Other: Delta, Echo
         Themes+Other: Foxtrot
         Subset:       Delta, Echo, Foxtrot

MSBuild is declarative. There are no loops. Don't think of Targets and Tasks as function calls.

In the example, the first four Message tasks use the Type metadata. Because the metadata is referenced, the MySpec item group collection is split into batches based on Type and the task is performed for each batch.

The conditions on each Message task are where the Type metadata is referenced which causes the batching. But the conditions also determine if the task is performed for a given batch. Note that the Message task for 'Misc' is not performed because nothing matches. But also note that the 'Themes+Other' task is run twice, once for each of two different batches of Type.

In many cases it is fine to perform a task multiple times with different batches. For the times when that is not acceptable, batching can be used to create a new item group collection. The SubSet item group is an example.

[mwpowellhtx]

Great response, thanks! I did do some background reading, I get it; they are not functions, unless they 'are' i.e. taking inputs returning outputs, but otherwise, yes, totally get it. Did not know I could do the batch-wise condition, this is awesome, just what I was looking for.