Add mobile telemetry hooks for Build target

[matouskozak]

Description

Adding simple mobile telemetry triggered by Build target for android, ios, maccatalyst, and tvos. Collecting: TargetPlatformIdentifier, RuntimeIdentifier, UseMonoRuntime, PublishAot, PublishReadyToRun, PublishReadyToRunComposite properties.

Sample Output Telemetry

{
    "EventName": "MobileProperties",
    "Properties": {
        "Invocation": "build",
        "TargetPlatformIdentifier": "android",
        "RuntimeIdentifier": "android-arm64",
        "UseMonoRuntime": "true",
        "PublishAot": "false",
        "PublishReadyToRun": "false",
        "PublishReadyToRunComposite": "false"
    },
    "Timestamp": "2025-08-31T14:07:24.070952+01:00",
    "ThreadId": 9,
    "Message": null,
    "HelpKeyword": null,
    "SenderName": null,
    "BuildEventContext": {
        "EvaluationId": -1,
        "NodeId": 1,
        "TargetId": 381,
        "ProjectContextId": 99,
        "TaskId": 333,
        "ProjectInstanceId": 4,
        "SubmissionId": 1,
        "BuildRequestId": -2053145140
    }
}

Testing

Tested locally by installing android workload to .dotnet/dotnet and running the following tests:

Publish:

[CoreMSBuildOnlyTheory]
[InlineData(ToolsetInfo.CurrentTargetFramework)]
public void It_collects_Mobile_properties_for_publish(string targetFramework)
{
    Type loggerType = typeof(LogTelemetryToStdOutForTest);
    var TelemetryTestLogger = new[]
        {
            "--property:TargetPlatformIdentifier=android",
            "--property:RuntimeIdentifier=android-arm64",
            "--property:UseMonoRuntime=true",
            "--property:PublishAot=false",
            "--property:PublishReadyToRun=false",
            "--property:PublishReadyToRunComposite=false",
            $"/Logger:{loggerType.FullName},{loggerType.GetTypeInfo().Assembly.Location}"
        };

    var testProject = CreateTestProject(targetFramework, "MobileTelemetryPublishTest");
    var testProjectInstance = _testAssetsManager.CreateTestProject(testProject);
    var publishCommand = new PublishCommand(testProjectInstance);
    publishCommand.Execute(TelemetryTestLogger).StdOut.Should.Contain(...)

Build:

[CoreMSBuildOnlyFact]
public void It_collects_Mobile_properties_for_build()
{
    string targetFramework = ToolsetInfo.CurrentTargetFramework;
    var testProject = new TestProject()
    {
        Name = "MobileTelemetryBuildTest",
        TargetFrameworks = targetFramework,
    };
    Type loggerType = typeof(LogTelemetryToStdOutForTest);
    var telemetryArgs = new[]
        {
            "--property:TargetPlatformIdentifier=android",
            "--property:RuntimeIdentifier=android-arm64",
            "--property:UseMonoRuntime=false",
            "--property:PublishAot=false",
            "--property:PublishReadyToRun=true",
            "--property:PublishReadyToRunComposite=true",
            $"/Logger:{loggerType.FullName},{loggerType.GetTypeInfo().Assembly.Location}"
        };
    var testAsset = _testAssetsManager.CreateTestProject(testProject);

    var buildCommand = new BuildCommand(testAsset);

    buildCommand
        .Execute(telemetryArgs)
        .StdOut.Should()
        .Contain(...)

Another testing was done by locally modified version of SDK, where I modified the .target files and verified that the mobile telemetry targets get executed for dotnet new android app.

Open Questions

1. How to setup tests using mobile workloads as part of the regular dotnet/sdk tests? (Instead of manually installing workload to .dotnet/dotnet)
2. Currently, the telemetry collects data for all commands that invoke Build target. How could we distinguish in the telemetry if the invocation came from dotnet build or dotnet publish?
3. How will this new telemetry data get propagated to Kusto?

---

I noticed that without "--property:TargetPlatformIdentifier=android", the TargetPlatformIdentifier in BeforeCommon.targets was left empty and the telemetry wasn't included. My concerns is if TargetPlatformIdentifier is populated soon enough so that the check in BeforeCommon.targets succeeds when building for mobile targets.

• After overwriting the modified target files in a local SDK copy, I can see the MobileTelemetry targets getting triggered, so I suppose the check is working.

[github-actions]

This PR is targeting main, which is now for .NET 11-facing work. If you intended to target .NET 10, either retarget this PR to release/10.0.1xx or make sure you backport the change to release/10.0.1xx after merging. See #50394 for more details.

[Copilot]

Pull Request Overview

This PR adds mobile telemetry hooks to collect build-time information for mobile platforms (Android, iOS, macOS Catalyst, and tvOS). The telemetry captures key properties like target platform, runtime identifier, and publishing configuration settings when the Build target is executed.

• Creates a new mobile telemetry target file that collects platform-specific properties
• Conditionally imports mobile telemetry only for mobile platforms in the build pipeline
• Registers the new "MobileProperties" telemetry event in the MSBuild logger

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
Microsoft.NET.Sdk.BeforeCommon.targets	Conditionally imports mobile telemetry targets for mobile platforms
Microsoft.NET.MobileTelemetry.targets	New file defining build telemetry collection for mobile properties
MSBuildLogger.cs	Adds MobileProperties event name to the telemetry logger

[Copilot]

[nitpick] The condition uses string equality comparisons with 'or' operators spanning multiple lines. Consider using an ItemGroup with an 'in' operator for better readability and maintainability: Condition="$(TargetPlatformIdentifier) != '' and '$(TargetPlatformIdentifier)' in 'android;ios;maccatalyst;tvos'"

Suggested change

	Condition="'$(TargetPlatformIdentifier)' == 'android' or
	'$(TargetPlatformIdentifier)' == 'ios' or
	'$(TargetPlatformIdentifier)' == 'maccatalyst' or
	'$(TargetPlatformIdentifier)' == 'tvos'" />
	Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' in 'android;ios;maccatalyst;tvos'" />

[Copilot]

[nitpick] The ItemGroup removes all MobileTelemetry items and then recreates them. This pattern could be simplified by using a condition on the target or by ensuring the ItemGroup is only populated once, which would be more efficient and clearer in intent.

Suggested change

	<ItemGroup>
	<MobileTelemetry Remove="@(MobileTelemetry)" />

[baronfel]

Triage/proposal:

• We should instead unify the current Publish properties and targetframeworkeval events into one combined data set
• We need to add a new SessionId value because the existing telemetry-context one isn't being forwarded for some reason
• We need clarity from @matouskozak's team about how you'd like to reason about multi-project and/or multi-TFM builds
  • We may be able to filter out transitive builds triggered by a top-level project if so.