[release/7.0] Set AssemblyName.ProcessorArchitecture for compatibilit…

…y. (#81101)

* Set AssemblyName.ProcessorArchitecture for compatibility.

* Simplified ProcArch computation.

* Make GetAssemblyName test more robust (#80878)

* undo AssemblyName.CoreCLR change

* Library servicing steps.

---------

Co-authored-by: vsadov <8218165+VSadov@users.noreply.github.com>
Co-authored-by: Vladimir Sadov <vsadov@microsoft.com>

src/libraries/System.Reflection.Metadata/src/System.Reflection.Metadata.csproj

@@ -9,6 +9,8 @@
 
 The System.Reflection.Metadata library is built-in as part of the shared framework in .NET Runtime. The package can be installed when you need to use it in other target frameworks.</PackageDescription>
  <PackageReadmeFile>README.md</PackageReadmeFile>
+ <ServicingVersion>1</ServicingVersion>
+ <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
  </PropertyGroup>
 
  <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->

src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/MetadataReader.netstandard.cs

@@ -85,6 +85,12 @@ public static unsafe AssemblyName GetAssemblyName(string assemblyFile)
  peReader = new PEReader((byte*)safeBuffer.DangerousGetHandle(), (int)safeBuffer.ByteLength);
  MetadataReader mdReader = peReader.GetMetadataReader(MetadataReaderOptions.None);
  AssemblyName assemblyName = mdReader.GetAssemblyDefinition().GetAssemblyName();
+
+ AssemblyFlags aFlags = mdReader.AssemblyTable.GetFlags();
+#pragma warning disable SYSLIB0037 // AssemblyName.ProcessorArchitecture is obsolete
+ assemblyName.ProcessorArchitecture = CalculateProcArch(peReader, aFlags);
+#pragma warning restore SYSLIB0037
+
  return assemblyName;
  }
  finally
@@ -101,6 +107,42 @@ public static unsafe AssemblyName GetAssemblyName(string assemblyFile)
  }
  }
 
+ private static ProcessorArchitecture CalculateProcArch(PEReader peReader, AssemblyFlags aFlags)
+ {
+ // 0x70 specifies "reference assembly".
+ // For these, CLR wants to return None as arch so they can be always loaded, regardless of process type.
+ if (((uint)aFlags & 0xF0) == 0x70)
+ return ProcessorArchitecture.None;
+
+ PEHeaders peHeaders = peReader.PEHeaders;
+ switch (peHeaders.CoffHeader.Machine)
+ {
+ case Machine.IA64:
+ return ProcessorArchitecture.IA64;
+ case Machine.Arm:
+ return ProcessorArchitecture.Arm;
+ case Machine.Amd64:
+ return ProcessorArchitecture.Amd64;
+ case Machine.I386:
+ {
+ CorFlags flags = peHeaders.CorHeader!.Flags;
+ if ((flags & CorFlags.ILOnly) != 0 &&
+ (flags & CorFlags.Requires32Bit) == 0)
+ {
+ // platform neutral.
+ return ProcessorArchitecture.MSIL;
+ }
+
+ // requires x86
+ return ProcessorArchitecture.X86;
+ }
+ }
+
+ // ProcessorArchitecture is a legacy API and does not cover other Machine kinds.
+ // For example ARM64 is not expressible
+ return ProcessorArchitecture.None;
+ }
+
  private static AssemblyNameFlags GetAssemblyNameFlags(AssemblyFlags flags)
  {
  AssemblyNameFlags assemblyNameFlags = AssemblyNameFlags.None;

src/libraries/System.Reflection.Metadata/tests/Metadata/MetadataReaderTests.cs

@@ -3090,8 +3090,13 @@ public void GetAssemblyName()
 
  if (PlatformDetection.HasAssemblyFiles)
  {
- Assembly a = typeof(MetadataReaderTests).Assembly;
- Assert.Equal(new AssemblyName(a.FullName).ToString(), MetadataReader.GetAssemblyName(AssemblyPathHelper.GetAssemblyLocation(a)).ToString());
+ Assembly a = typeof(MetadataReader).Assembly;
+ AssemblyName name = MetadataReader.GetAssemblyName(AssemblyPathHelper.GetAssemblyLocation(a));
+ Assert.Equal(new AssemblyName(a.FullName).ToString(), name.ToString());
+
+#pragma warning disable SYSLIB0037 // AssemblyName.ProcessorArchitecture is obsolete
+ Assert.Equal(ProcessorArchitecture.MSIL, name.ProcessorArchitecture);
+#pragma warning restore SYSLIB0037
  }
  }
  }