Aspire E2E Exception After Installing 10.0 P7 And Running Existing Projects

Hey everyone! We've got a bit of a situation on our hands with Aspire, and I wanted to break it down for you in a way that's easy to understand. We're seeing an issue where, after installing SDK 10.0 P7, running an existing 9.0 or 10.0 P6 Aspire project throws an exception in the CLI, and the dashboard just doesn't load correctly. It's a bit of a head-scratcher, but let's dive into the details.

Regression Information: The Scope of the Issue

This regression issue isn't just a one-off; it's showing up in a few different configurations, which is something we really need to address. We've seen it rear its head in the following setups:

• SDK 9.0.303 + Aspire 9.3.1 + SDK 10.0 P6
• SDK 9.0.303 + Aspire 9.4.0 + SDK 10.0 P6
• SDK 10.0 P6 + Aspire 9.4.0 + SDK 10.0 P7

This pattern tells us that it's not isolated to a single version combination, but rather a broader interaction between these SDKs and Aspire versions. Understanding the scope is the first step in tackling this bug, so knowing it spans these configurations gives us a good starting point for our investigation.

Reproduction Steps: How to Make the Bug Appear

So, how do we actually make this bug show up? Here's a step-by-step guide to reproduce the issue. This is crucial because if we can reliably reproduce it, we can reliably test our fixes. Let's walk through the process:

1. Start with a Clean Slate: We begin with a clean machine – a Win11 x64 24h2 ENU setup. This ensures we're all starting from the same baseline, eliminating any potential environmental factors. A clean slate helps us isolate the problem to the specific steps we're testing.
2. Install SDK 9.0.303 and Aspire 9.4.0: Next, we install the older SDK and Aspire version. This is important because we're seeing the issue arise when transitioning between versions, so we need to set up the initial environment.
3. Trust the Dev Cert: Run dotnet dev-certs https --trust to trust the development certificate for SDK 9.0.303. This is a key step because certificate issues can often lead to problems with local development environments. By trusting the cert, we rule out that potential cause.
4. Create and Run an Aspire Starter App: We create a basic Aspire Starter App and run it. The expectation here is that it runs successfully. This confirms that our initial environment is working as expected before we introduce the problematic SDK version.
5. Install SDK 10.0 P7: Now, we install the problematic SDK version – 10.0 P7. Crucially, we do not run dotnet dev-certs https --trust for this SDK. This is a deliberate omission, as we suspect certificate handling might be part of the issue.
6. Open and Run the Existing Project: We open the project we created in step 4 and try to run it using dotnet run. We then try to open the URL in a browser. This is where we expect to see the issue manifest itself.

By following these steps, you should be able to reproduce the error consistently. Remember, the key to fixing a bug is understanding how to make it happen on demand.

Important Notes: Key Observations About the Issue

Before we jump into potential solutions, there are a few critical observations about this issue that are worth highlighting. These nuances can give us clues about what's going on under the hood:

1. First Run Phenomenon: This issue primarily crops up on the very first run after installing SDK 10.0 P7. Subsequent runs often don't exhibit the same problem. This suggests that there might be some kind of initialization or configuration issue that only occurs once after the new SDK is installed. It's like a first-time setup process going awry.
2. The Dev Cert Factor: If you open a project that hasn't been run since the 9.0.303 dev cert was established, or a project that predates the cert's establishment, the issue won't reproduce. This strongly points to a connection between the development certificate and the problem. It seems that the way the project interacts with the cert after the SDK update is where things go wrong.
3. Adding the 10.0 P7 Cert as a Workaround: Interestingly, adding the 10.0 P7 dev cert after the fact seems to alleviate the issue. If you open the existing 9.0 project and run it after trusting the new certificate, the problem disappears. This workaround gives us a valuable hint: it suggests that the issue might stem from a conflict or missing link in the certificate chain when the project is initially run under the new SDK.

These notes are like breadcrumbs, guiding us toward the root cause of the problem. By understanding the conditions under which the issue arises and disappears, we can start to form hypotheses about what's really happening.

Actual Behavior: What We See When the Bug Occurs

Okay, so we've set the stage and reproduced the bug. But what does it actually look like when it happens? Well, the first thing you'll notice is that the page is blank. It's like the dashboard just refuses to load, leaving you staring at a big, empty space. Not exactly the Aspire experience we're hoping for, right?

But wait, there's more! If you try refreshing the page, things get even more interesting. You'll likely encounter an error message. In this specific case, we're seeing a Microsoft.JSInterop.JSException. This exception tells us that something went wrong while trying to run JavaScript code in the browser. The error message goes on to say:

Failed to fetch dynamically imported module: https://localhost:17111/_content/Microsoft.FluentUI.AspNetCore.Components/Components/Anchor/FluentAnchor.razor.js?v=4.11.9.25128
TypeError: Failed to fetch dynamically imported module: https://localhost:17111/_content/Microsoft.FluentUI.AspNetCore.Components/Components/Anchor/FluentAnchor.razor.js?v=4.11.9.25128

This is a mouthful, but the key takeaway here is that the browser is failing to fetch a dynamically imported JavaScript module. Specifically, it's having trouble with a module related to FluentAnchor.razor.js, which is part of the Microsoft FluentUI library. This library is used for building the Aspire dashboard's user interface, so if it can't load, the dashboard is going to have problems.

Looking at the stack trace, we can see the error originating in Microsoft.FluentUI.AspNetCore.Components.FluentAnchor.OnAfterRenderAsync. This suggests that the issue is happening during the rendering of a FluentAnchor component, which is a basic UI element like a link or button.

Interestingly, if you stop the application and run it again, the page often displays normally. This further reinforces the idea that the issue is related to some kind of initial setup or caching problem.

Expected Behavior: What We Want to See

Now, let's talk about what we expect to happen. Ideally, when we run an existing Aspire project after installing a new SDK, everything should just work. We shouldn't have to jump through hoops or deal with cryptic error messages. The project should run successfully, and the dashboard should load without any issues.

That's the gold standard we're aiming for: a seamless experience where Aspire projects are resilient to SDK updates. We want to avoid situations where developers are left scratching their heads, wondering why their dashboards are blank or throwing JavaScript errors.

Diving Deeper: Potential Causes and Solutions

Okay, so we've got a good handle on the problem. We know how to reproduce it, we know what it looks like, and we know what the expected behavior is. Now it's time to put on our detective hats and start thinking about potential causes and solutions.

Given the clues we've gathered, here are a few hypotheses we can explore:

1. Certificate Mishaps: The fact that the issue often disappears after trusting the 10.0 P7 dev cert suggests that certificate handling is a prime suspect. It's possible that the new SDK is introducing changes to how certificates are managed, and existing projects might not be correctly picking up the new certificate. This could lead to the browser refusing to load resources from localhost due to security concerns.
2. Caching Conundrums: The