Expose through extension methods maui build and launch arguments - #19572

Previously missed (1) — in code that hasn't changed since the last review.

src/Aspire.Hosting.Maui/MauiBuildArgumentsExtensions.cs:112

• This example recommends overriding NoBuild=true, but that flag is required by the serialized build queue: the semaphore is released when DCP reports the launch process Running, before any launch-time build finishes, allowing the next target to build concurrently. Keep NoBuild=true and use a non-build-triggering launch property in the example, unless the queue lifecycle is redesigned.

This issue also appears on line 143 of the same file.

    /// <example>
    /// Force a build during launch by overriding the default <c>-p:NoBuild=true</c>:
    /// <code lang="csharp">
    /// maui.AddAndroidEmulator("emulator")
    ///     .WithMauiLaunchArguments(context => context.Arguments.Add("-p:NoBuild=false"));
    /// </code>

src/Aspire.Hosting.Maui/Lifecycle/MauiBuildQueueEventSubscriber.cs:293

• This is not idempotent as the new regression test expects. After the first BeforeStartEvent, launchOverride is the replacement annotation containing the callback's additions, so a second event copies those edited arguments and applies the callbacks again (and the test helper also registers another subscriber). The WithMauiLaunchArguments_MultipleStarts_DoNotAccumulate assertion will therefore observe duplicate -p:NoBuild=false entries. Preserve the pristine override separately or mark the launch callbacks as applied so repeated startup processing cannot reapply them.

        var arguments = new List<string>(launchOverride.Arguments);

src/Aspire.Hosting.Maui/README.md:244

• This TypeScript example does not match the generated SDK. A getter-only IList<string> is exposed as the async context.arguments() method returning an AspireList<string>, whose mutation API is add; context.arguments.push(...) therefore does not compile. Fetch the list and await add in an async callback.

    .withMauiBuildArguments(context => { context.arguments.push("-p:MyProperty=Value"); });

src/Aspire.Hosting.Maui/MauiBuildArgumentsExtensions.cs:42

• These are new exported callback APIs, but the PR only adds C# tests; the existing MAUI polyglot AppHost does not exercise either generated method or its callback context. Add a TypeScript polyglot scenario that mutates the generated arguments editor. This is especially important here because the README currently uses a generated API shape that does not compile.

    [AspireExport]
    public static IResourceBuilder<T> WithMauiBuildArguments<T>(
        this IResourceBuilder<T> builder,
        Func<MauiBuildArgumentsCallbackContext, Task> callback)

src/Aspire.Hosting.Maui/README.md:258

• This TypeScript example does not match the generated SDK. A getter-only IList<string> is exposed as the async context.arguments() method returning an AspireList<string>, whose mutation API is add; context.arguments.push(...) therefore does not compile. Fetch the list and await add in an async callback.

    .withMauiLaunchArguments(context => { context.arguments.push("-p:NoBuild=false"); });

src/Aspire.Hosting.Maui/MauiBuildArgumentsExtensions.cs:148

• This example also recommends overriding NoBuild=true, which breaks the build queue's serialization because the semaphore can be released as soon as the launch process reports Running, before launch-time compilation completes. Keep NoBuild=true and demonstrate a property that does not trigger another build.

    /// <example>
    /// Force a build during launch by overriding the default <c>-p:NoBuild=true</c>:
    /// <code lang="csharp">
    /// maui.AddAndroidEmulator("emulator")
    ///     .WithMauiLaunchArguments(context => context.Arguments.Add("-p:NoBuild=false"));
    /// </code>

Previously missed (2) — in code that hasn't changed since the last review.

src/Aspire.Hosting.Maui/Lifecycle/MauiBuildQueueEventSubscriber.cs:293

• Repeated application is not idempotent: this copies the last override, which already contains the prior callback result. An append-style launch callback therefore adds its argument again whenever BeforeStartEvent is published again, contrary to the documented contract and the new multiple-start test. Preserve the pristine launch override separately and rebuild the callback result from that baseline each time.

        var arguments = new List<string>(launchOverride.Arguments);

src/Aspire.Hosting.Maui/MauiBuildArgumentsCallbackContext.cs:51

• This token is not always tied to a resource start. Launch callbacks receive the BeforeStartEvent token, while build callbacks receive the linked per-resource token, so the current public documentation promises cancellation semantics that launch callbacks do not have.

    /// Gets a token that is cancelled if the resource start is cancelled.

src/Aspire.Hosting.Maui/README.md:258

• This TypeScript sample uses an API shape the generated SDK does not provide. arguments is an async getter returning an AspireList<string>, whose mutation method is asynchronous add; it is not an array with push.

    .withMauiLaunchArguments(context => { context.arguments.push("-p:MyProperty=Value"); });

src/Aspire.Hosting.Maui/MauiBuildArgumentsExtensions.cs:39

• The new exported callback contract has only C# tests that invoke annotations directly. Because the callback context projects a live mutable list into generated SDKs, add ATS/TypeScript generation coverage for both methods and the arguments(): Promise<AspireList<string>> mutation path; this would also catch the invalid TypeScript examples in this PR.

    [AspireExport]

Previously missed (1) — in code that hasn't changed since the last review.

src/Aspire.Hosting.Maui/MauiBuildArgumentsCallbackContext.cs:51

• This description is inaccurate for launch callbacks: they run from BeforeStartEvent and receive the application-start cancellation token, before any individual resource start can be canceled. Describe this as cancellation of the current callback operation so the documentation is correct for both build and launch steps.

    /// <summary>
    /// Gets a token that is cancelled if the resource start is cancelled.
    /// </summary>

src/Aspire.Hosting.Maui/README.md:264

• This TypeScript fluent call is also left unawaited, so the sample relies on implicit promise flushing and defers failures. Await the registration chain directly.

mauiApp.addAndroidEmulator("emulator")
    .withMauiLaunchArguments(async context => {
        const args = await context.arguments();
        await args.add("-p:MyProperty=Value");
    });