Troubleshooting Android CoreCLR Test Host Issues With Runtimeconfig.json

July 29, 2025 by StackCamp Team 73 views

Troubleshooting Android CoreCLR Test Host: Runtimeconfig.json Not Found

Hey guys! Ever run into a situation where your Android CoreCLR test host just can't seem to find that elusive runtimeconfig.json file? It's a real head-scratcher, but don't worry, we're going to dive deep into this issue and figure out what's going on. This article will explore the common causes, potential solutions, and how to reproduce the problem, so you can get your tests running smoothly again.

Problem Description

So, the main issue we're tackling today is that when you're building an Android app using CoreCLR, specifically the sample app located at src/mono/sample/Android/AndroidSampleApp.csproj, the test host sometimes struggles to locate the runtimeconfig.json file. Now, this might seem odd because, in some other test projects like Invariant.Tests.csproj or those enabled in issue #117980, everything works just fine. So, what's the deal?

The likely culprit lies within the ApkBuilder.cs file, specifically around line 689. Here, the code attempts to find the runtimeconfig.json file using the [appname].runtimeconfig.json naming convention, as suggested by the official documentation. This approach works in many cases, but there are instances, like our sample app, where the generated .json file follows a different naming pattern: [assemblyname].runtimeconfig.json. To put it simply, the application's name might be HelloAndroid, but the assembly is named AndroidSampleApp. Consequently, the system generates AndroidSampleApp.runtimeconfig.json, while the test host is searching for HelloAndroid.runtimeconfig.json, leading to a frustrating "file not found" error. This discrepancy between the expected and actual file names is the root cause of the problem, and resolving it will ensure that the test host can correctly locate and utilize the runtime configuration.

Potential Solutions Explored

Alright, so we've identified the problem. Now, let's brainstorm some solutions to get this runtimeconfig.json fiasco sorted out. We've got a couple of options on the table, each with its own set of considerations. It's crucial to weigh these approaches carefully to determine the best path forward.

Fallback to Assembly Name

One option is to have the test host first look for [appname].runtimeconfig.json, and if it doesn't find it, fallback to searching for [assemblyname].runtimeconfig.json. This seems like a reasonable approach, right? If the standard naming convention doesn't pan out, we try the assembly name as a backup. However, this raises a crucial question: Is this the correct behavior? The documentation clearly states that the file should be named [appname].runtimeconfig.json. So, are we potentially masking an underlying issue or deviating from the intended naming convention? This is something we need to consider carefully. We must ensure that adopting this fallback mechanism aligns with the overall design principles and doesn't introduce any unexpected side effects. It's essential to thoroughly evaluate the implications of this approach before implementing it to ensure that it provides a robust and reliable solution.

Load Runtimeconfig.bin

Another intriguing option is to ditch the .json file altogether and instead load the runtimeconfig.bin file. This approach neatly sidesteps the naming problem, as we're no longer reliant on a specific filename. The source code for generating this binary file can be found in src/tasks/MonoTargetsTasks/RuntimeConfigParser/RuntimeConfigParser.cs. This approach has the potential to simplify the process and eliminate the risk of naming conflicts. The key here is to ensure that loading the binary file provides the same functionality and configuration options as the .json file. We need to verify that this method fully satisfies the requirements and doesn't introduce any limitations. Thorough testing and evaluation are essential to ensure that this approach is a viable and reliable alternative to using the .json file.

Steps to Reproduce the Issue

Okay, let's get practical. If you want to see this issue in action, here's how you can reproduce it. This is super helpful for understanding the problem firsthand and verifying any potential fixes. By following these steps, you can replicate the exact scenario where the runtimeconfig.json file isn't found, allowing for a more targeted and effective troubleshooting process. Reproducing the issue ensures that you are addressing the root cause and that any implemented solutions are genuinely effective.

Build the Runtime: First, you'll need to build the runtime using the following command:
```
build.sh --os android -a x64 -s clr.runtime+clr.alljits+clr.corelib+clr.nativecorelib+clr.tools+clr.packages+libs+libs.tests+host+packs -c Release /p:ArchiveTests=true /p:RunSmokeTestsOnly=True
```
This command sets up the environment and compiles the necessary components for the Android runtime. It's a crucial step in ensuring that you have the correct build configuration to reproduce the issue accurately. Make sure you execute this command in the appropriate directory and that all dependencies are correctly installed. A successful build is the foundation for replicating the problem and testing potential solutions.
Build the Sample App: Next, build the sample app with this command:
```
make BUILD_CONFIG=Release TARGET_ARCH=x64 RUNTIME_FLAVOR=CoreCLR DEPLOY_AND_RUN=false run -C src/mono/sample/Android
```
This command specifically builds the AndroidSampleApp, which is where we've seen this issue pop up. The flags ensure that we're building a release configuration for the x64 architecture, using the CoreCLR runtime flavor. The DEPLOY_AND_RUN=false flag prevents the app from being automatically deployed and run, which is useful for focusing on the build process and file generation. By building the sample app in this controlled environment, you can closely observe the files that are created and verify whether the runtimeconfig.json file is named correctly. This step is critical for confirming the problem and testing potential fixes.

Expected vs. Actual Behavior

So, what should happen, and what actually happens? Let's break it down. Understanding the discrepancy between expected and actual behavior is key to diagnosing the issue and verifying that any implemented solutions are effective. It's not enough to just fix the immediate problem; we need to ensure that the fix aligns with the intended behavior of the system.

Expected Behavior

Ideally, the test host should be able to find the HelloAndroid.runtimeconfig.json file without any hiccups. This is the scenario we're aiming for: a smooth, trouble-free test run. The expectation is that the runtime configuration file, which contains critical settings for the application, is correctly located and loaded by the test host. This ensures that the application runs with the intended configuration and that tests can be executed reliably. A properly functioning test host is essential for maintaining the quality and stability of the application.

Actual Behavior

In reality, the HelloAndroid.runtimeconfig.json file goes missing, leading to an error message that looks something like this:

Error while parsing runtime config at `artifacts/bin/AndroidSampleApp/x64/Release/android-x64/publish/HelloAndroid.runtimeconfig.json`: Could not find file `artifacts/bin/AndroidSampleApp/x64/Release/android-x64/publish/HelloAndroid.runtimeconfig.json`

Notice how the error message explicitly states that the HelloAndroid.runtimeconfig.json file cannot be found. This clearly indicates that the test host is looking for a file with this specific name, but it's not present in the expected location. This discrepancy between the expected and actual behavior is a direct consequence of the naming mismatch we discussed earlier. The system is generating a runtimeconfig.json file with a different name, causing the test host to fail in its attempt to locate and load the configuration. This error message serves as a crucial piece of evidence in diagnosing the issue and verifying that any proposed solutions correctly address the underlying problem.

Conclusion

Alright, guys, we've covered a lot of ground here! We've identified the issue, explored potential solutions, and even learned how to reproduce the problem. Hopefully, this deep dive into the Android CoreCLR test host's struggle with runtimeconfig.json has shed some light on the situation. Remember, the key takeaway is that the naming convention mismatch between the expected [appname].runtimeconfig.json and the actual [assemblyname].runtimeconfig.json is the root cause. By understanding this, we can move forward with confidence in implementing the right fix. Whether it's falling back to the assembly name or loading the runtimeconfig.bin file, we're now better equipped to tackle this challenge. Keep experimenting, keep learning, and happy coding!