Required library libhostfxr.so could not be found

[ckuehl]

Related to #446, I'm seeing an issue when setting --msbuild-parameters /p:PreserveCompilationContext=true at the end of my dotnet lambda deploy-serverless command. I am using Amazon.Lambda.RuntimeSupport to run a .Net Core 2.2 app. When executing the Lambda function, I receive the following error:

A fatal error occurred, the required library libhostfxr.so could not be found.
If this is a self-contained application, that library should exist in [/var/task/].
If this is a framework-dependent application, install the runtime in the default location [/usr/share/dotnet] or use the DOTNET_ROOT environment variable to specify the runtime location.

I need this set as I use the https://github.com/toddams/RazorLight library for some of our HTML email templates. Is there a way to use p:PreserveCompilationContext successfully with .Net Core 2.2 and Lambda?

[normj]

Assuming your created your Custom Runtime Lambda project from one of our templates check out the aws-lambda-tools-defaults.json file and see that it also has a value for msbuild-parameters set to -self-contained true. An awkward situation is when you set --msbuild-parameters on the command line it replaces what is set in aws-lambda-tools-defaults.json so the self contained switch doesn't get included.

Can you either include --self-contained true to the value you are setting for --msbuild-parameters or add /p:PreserveCompilationContext=true to msbuild-parameters in aws-lambda-tools-defaults.json.

Due to an old quirk from the .NET Core 1.0 days and the fact you are using razor pages with your Lambda function you also might need to set the runtime with msbuild parameters. To do that add -r rhel.7.2-x64 to the msbuild parameters string. Now that .NET Core 1.0 is officially deprecated I plan on fixing that old quick.

[ckuehl]

Awesome - that seems to have fixed it. I wasn't aware that the values would override each other, so placing both flags in the aws-lambda-tools-defaults.json file worked. Thanks for the help!