Aspnetcore doesn't look for linux-musl nupkgs when building on linux-musl platform

[ayakael]

Aspnetcore looks for linux-x64 version of nupkgs that, under Alpine, should be linux-musl-x64.

Provisional patch follows:

From 9f21622ae208f49adddf9e8465295229661579ec Mon Sep 17 00:00:00 2001
From: "build@apk-groulx" <build@apk-groulx.praxis>
Date: Thu, 20 Jan 2022 01:12:07 +0000
Subject: [PATCH 1/1] build_fix-musl-build

---
 repos/aspnetcore.proj | 1 +
 repos/installer.proj  | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/repos/aspnetcore.proj b/repos/aspnetcore.proj
index ad9d77885..0cefccee1 100644
--- a/repos/aspnetcore.proj
+++ b/repos/aspnetcore.proj
@@ -5,6 +5,7 @@
     <!-- StandardSourceBuildArgs include -publish which is not supported by the aspnetcore build script. -->
     <BuildCommandArgs>$(StandardSourceBuildArgs.Replace('--publish', ''))</BuildCommandArgs>
     <!-- The arch flag (defaults to x64) overrides any value of TargetArchitecture that we might set -->
+    <BuildCommandArgs>$(BuildCommandArgs) --os-name linux-musl</BuildCommandArgs>
     <BuildCommandArgs>$(BuildCommandArgs) --arch $(Platform)</BuildCommandArgs>
     <BuildCommandArgs>$(BuildCommandArgs) --no-build-repo-tasks</BuildCommandArgs>
     <BuildCommandArgs>$(BuildCommandArgs) /p:BuildNodeJs=false</BuildCommandArgs>
diff --git a/repos/installer.proj b/repos/installer.proj
index 712d7cd14..cca5295f9 100644
--- a/repos/installer.proj
+++ b/repos/installer.proj
@@ -25,7 +25,7 @@
     <BuildCommandArgs Condition="'$(TargetOS)' == 'Linux'">$(BuildCommandArgs) /p:Rid=$(TargetRid)</BuildCommandArgs>
     <BuildCommandArgs>$(BuildCommandArgs) /p:DOTNET_INSTALL_DIR=$(DotNetCliToolDir)</BuildCommandArgs>
 
-    <BuildCommandArgs Condition="'$(TargetOS)' == 'Linux'">$(BuildCommandArgs) /p:AspNetCoreSharedFxInstallerRid=linux-$(Platform)</BuildCommandArgs>
+    <BuildCommandArgs Condition="'$(TargetOS)' == 'Linux'">$(BuildCommandArgs) /p:AspNetCoreSharedFxInstallerRid=linux-musl-$(Platform)</BuildCommandArgs>
     <!-- core-sdk always wants to build portable on OSX and FreeBSD -->
     <BuildCommandArgs Condition="'$(TargetOS)' == 'FreeBSD'">$(BuildCommandArgs) /p:CoreSetupRid=freebsd-x64 /p:PortableBuild=true</BuildCommandArgs>
     <BuildCommandArgs Condition="'$(TargetOS)' == 'OSX'">$(BuildCommandArgs) /p:CoreSetupRid=osx-x64</BuildCommandArgs>
-- 

Better implementation would involve, either Aspnetcore automatically setting os-name to linux-musl when building, or repos/aspnetcore.proj automaticallty adds the above BuildCommandArg. Ditto on repos/installer.proj for setting AspNetCoreSharedFxInstallerRid,

Made as part of Alpine Linux dotnet6 packaging project, see dotnet/source-build#2782

[omajid]

Could/should we push this logic/fix into aspnetcore itself? I identified several other cases that would break in the ASP.NET Core builds a few months ago, including linux-musl-arm64: #37400

[MichaelSimons]

[Source-build triage] We agree with @omajid's suggestion that the preferred place to fix this is within aspnetcore itself. If guidance is needed, reach out to @dotnet/source-build-internal.

[mkArtakMSFT]

[Source-build triage] We agree with @omajid's suggestion that the preferred place to fix this is within aspnetcore itself. If guidance is needed, reach out to @dotnet/source-build-internal.

Thanks @MichaelSimons. Do you think this is something we must fix? I'm trying to gauge the urgency and importance of this.

[MichaelSimons]

@mkArtakMSFT - Must is a little strong. I would classify this as something we should fix/accept. This makes is easier for distro maintainers to build .NET from source. With the unified build investments being made in .NET 8 we want to support a true open source upstream vs what we have today where upstream is mostly Microsoft's variant.

[ayakael]

Considering the move to portable RIDs as default for source-build starting with .NET8, this should be worked on. Right now, I'm unable to build dotnet8 when TargetRid=linux-musl-x64 rather than alpine-3.18-x64. I've identified eng/Common.props as the culprit, as it sets TargetOsName=linux rather than the expected TargetOsName=linux-musl. Logics should be put in place to detect if the platform is Musl, and set TargetOsName=linux-musl

[ayakael]

A related issue is #37400, failing the build on non-x64 platform. A workaround is setting /p:BuildOSName=linux-musl in addition to --os-name linux-musl. The installer changes in the the first workaround wasn't necessary