Update construct seems to update all items regardless of match when run in target

[nguerrera]

<Project>
  <ItemGroup>
     <X Include="A;B;C" />
     <X Update="B" Metadata="Just on B" />
     <X Update="NonExistent" Metadata="Useless" />
  </ItemGroup>

  <Target Name="Build">
    <Warning Text="Before in-target update: %(X.Identity) %(X.Metadata)" />
    
   <ItemGroup>
      <X Update="A" Metadata="Just on A" />
      <X Update="NonExistent" Metadata="Huh" />
   </ItemGroup>
      
   <Warning Text="After in-target update: %(X.Identity) %(X.Metadata)" />
 </Target>
</Project>

Expected after target runs:

• A has Metadata= "Just on A" and B has Metadata "Just on B", C has no Metadata=""

Actual:

• They all have Metadata="Huh"

C:\temp\test.proj(10,5): warning : Before in-target update: A
C:\temp\test.proj(10,5): warning : Before in-target update: B Just on B
C:\temp\test.proj(10,5): warning : Before in-target update: C
C:\temp\test.proj(17,4): warning : After in-target update: A Huh
C:\temp\test.proj(17,4): warning : After in-target update: B Huh
C:\temp\test.proj(17,4): warning : After in-target update: C Huh

@AndyGerlicher @rainersigwald

[davkean]

tag @cdmihai

[rainersigwald]

I think this is a bad interaction between metadata-as-attributes and the fact that items are handled differently in targets.

Update was possible before the Update attribute, but only in targets. Inside a target you can use the old form (set metadata as though in an ItemDefinitionGroup, batching over the items with conditions).

      <X Metadata="Just on A" Condition="'%(X.Identity)' == 'A'" />
      <X Metadata="Huh" Condition="'%(X.Identity)' == 'NonExistent'" />

That's the best workaround for this.

Surprising things:

• This isn't an error. We didn't implement Update attributes inside targets, and I would have expected this to report "invalid syntax". I suspect it's not because of metadata-as-attributes, but
• Update doesn't appear to actually be getting set as metadata. Maybe we're correctly rejecting it as a reserved not-eligible-for-as-attribute metadata name, but not pushing up an error?

[nguerrera]

This needs to at least be an error for RTW.

I have a case (investigating perf issue with GetTargetFrameworkProperties) where it is very difficult to express as a condition.

Basically, I get a item group back from <MSBuild> task where the items have OriginalItemSpec pointing back to the project items and I want to update the project items passed in with metadata returned.

I imagined something like this would work and read nicely:

<MSBuild Projects="@(X)">
   <Output TaskParameter="TargetOutputs" ItemName="Y" />
</MSBuild>
<ItemGroup>
    <X Update="%(Y.OriginalItemSpec)">
        <Metadata>%(Y.Metadata)</Metadata>
   </X>
</ItemGroup>

Variants using conditions did not work out either:

<X  Metadata="%(Y.Metadata)" Condition="%(X.Identity) == %(Y.OriginalItemSpec)" />

I'm still trying to wrap my head around #1018 (comment) and I can't get it to work. I'd love to find a readable expression of this pattern.

[nguerrera]

Btw, it does error out if I use Update="" saying Update can't be empty so it partially knows this is special and not metadata.

[rainersigwald]

Beat my head against this for quite a while. I think you should just write a Task to do this. The syntax you want wouldn't do what you expect either due to the vagaries of batching rules.

[nguerrera]

OK. I'll write a task. :) Still pushing for that error in RTW.

[cdmihai]

Included in #1124

[nguerrera]

NOTE: This was closed because it's a subset of #1124, not because it was fixed.

[jimitndiaye]

This needs to at least be an error for RTW.

I have a case (investigating perf issue with GetTargetFrameworkProperties) where it is very difficult to express as a condition.

Basically, I get a item group back from <MSBuild> task where the items have OriginalItemSpec pointing back to the project items and I want to update the project items passed in with metadata returned.

I imagined something like this would work and read nicely:

<MSBuild Projects="@(X)">
   <Output TaskParameter="TargetOutputs" ItemName="Y" />
</MSBuild>
<ItemGroup>
    <X Update="%(Y.OriginalItemSpec)">
        <Metadata>%(Y.Metadata)</Metadata>
   </X>
</ItemGroup>

Variants using conditions did not work out either:

<X  Metadata="%(Y.Metadata)" Condition="%(X.Identity) == %(Y.OriginalItemSpec)" />

I'm still trying to wrap my head around #1018 (comment) and I can't get it to work. I'd love to find a readable expression of this pattern.

I'm trying to do exactly what @nguerrera is trying to do here with similar results.

[gulbanana]

I've just run across this and it was extremely confusing.