AfterTargets hook runs before target body when Condition-skipped target re-runs with Condition true

[sbomer]

This may be by design (see referenced issues below) but I found this very confusing, so wanted to make sure we have an issue for this specific problem.

Repro

<Project>
  <Target Name="Build" DependsOnTargets="Work;Enable;Second" />
  <Target Name="Work" Condition=" '$(Enabled)' == 'true' ">
    <Message Importance="high" Text="1. Work ran" />
  </Target>
  <Target Name="Hook" AfterTargets="Work">
    <Message Importance="high" Text="2. Hook ran" />
  </Target>
  <Target Name="Enable">
    <PropertyGroup>
      <Enabled>true</Enabled>
    </PropertyGroup>
  </Target>
  <Target Name="Second" DependsOnTargets="Work" />
</Project>

$ dotnet msbuild repro.proj -v:n

Expected: 1. Work ran before 2. Hook ran
Actual: 2. Hook ran before 1. Work ran

Hook fires on the first (Condition-false) invocation of Work, before Work has ever executed. When Work actually runs on the second invocation (after Enable sets the property), Hook does not fire again.

Analysis

Two documented behaviors interact to produce this:

1. AfterTargets fires on skipped targets — "After the target is executed or skipped, any other target that lists it in an AfterTargets attribute is run."
2. Condition-skipped targets can re-run — "If a target is skipped because its Condition evaluates to false, it can still be executed if invoked later with Condition true."

The target gets a second chance, but its hooks don't.

This came up while investigating an incremental build issue in xamarin-android.

Related

• Targets hooked BeforeTargets a conditioned target run after instead #8788 — BeforeTargets ordering wrong on Condition-false target (fixed)
• Confusing and inconsistent behavior around AfterTargets="Build" in referenced projects #11784 — AfterTargets not awaited by second caller in parallel builds (open)