[wasm] Allow to build browser in library mode

src/mono/browser/build/BrowserWasmApp.targets

@@ -63,6 +63,15 @@
     <ProjectCapability Include="DotNetCoreWeb"/>
   </ItemGroup>
 
+  <!-- When trimming non-exe projects, root the whole intermediate assembly. -->
+  <Target Name="_RootEntireIntermediateAssembly" AfterTargets="PrepareForILLink" BeforeTargets="_RunILLink" Condition="'$(RuntimeIdentifier)' == 'browser-wasm' And '$(OutputType)' == 'Library'">
+    <ItemGroup>
+      <TrimmerRootAssembly Condition="'%(Identity)' == '@(IntermediateAssembly)'">
+        <RootMode>all</RootMode>
+      </TrimmerRootAssembly>
+    </ItemGroup>
+  </Target>
+
   <Target Name="_GetWasmGenerateAppBundleDependencies">
     <Warning Condition="'$(InvariantGlobalization)' == 'true' and '$(HybridGlobalization)' == 'true'" Text="%24(HybridGlobalization) has no effect when %24(InvariantGlobalization) is set to true." />
     <Warning Condition="'$(WasmIcuDataFileName)' != '' and '$(HybridGlobalization)' == 'true'" Text="%24(WasmIcuDataFileName) has no effect when %24(HybridGlobalization) is set to true." />

src/mono/wasi/wasi.proj

@@ -67,7 +67,8 @@
       PInvokeModules="@(WasmPInvokeModule)"
       PInvokeOutputPath="$(WasmPInvokeTablePath)"
       InterpToNativeOutputPath="$(WasmInterpToNativeTablePath)"
-      IsLibraryMode="$(_IsLibraryMode)">
+      IsLibraryMode="$(_IsLibraryMode)"
+      RuntimeIdentifier="$(RuntimeIdentifier)">
       <Output TaskParameter="FileWrites" ItemName="FileWrites" />
     </ManagedToNativeGenerator>
   </Target>

src/mono/wasm/build/WasmApp.Common.targets

@@ -798,7 +798,8 @@
       PInvokeOutputPath="$(_WasmPInvokeTablePath)"
       InterpToNativeOutputPath="$(_WasmInterpToNativeTablePath)"
       CacheFilePath="$(_WasmM2NCachePath)"
-      IsLibraryMode="$(_IsLibraryMode)">
+      IsLibraryMode="$(_IsLibraryMode)"
+      RuntimeIdentifier="$(RuntimeIdentifier)">
       <Output TaskParameter="FileWrites" ItemName="FileWrites" />
     </ManagedToNativeGenerator>
   </Target>

src/tasks/WasmAppBuilder/ManagedToNativeGenerator.cs

@@ -35,6 +35,8 @@ public class ManagedToNativeGenerator : Task
 
     public bool IsLibraryMode { get; set; }
 
+    public string RuntimeIdentifier { get; set; } = string.Empty;
+
     [Output]
     public string[]? FileWrites { get; private set; }
 
@@ -71,7 +73,7 @@ private void ExecuteInternal(LogAdapter log)
         List<string> managedAssemblies = FilterOutUnmanagedBinaries(Assemblies);
         if (ShouldRun(managedAssemblies))
         {
-            var pinvoke = new PInvokeTableGenerator(FixupSymbolName, log, IsLibraryMode);
+            var pinvoke = new PInvokeTableGenerator(FixupSymbolName, log, IsLibraryMode, RuntimeIdentifier);
             var icall = new IcallTableGenerator(RuntimeIcallTableFile, FixupSymbolName, log);
 
             var resolver = new PathAssemblyResolver(managedAssemblies);

src/tasks/WasmAppBuilder/PInvokeTableGenerator.cs

@@ -26,13 +26,15 @@ internal sealed class PInvokeTableGenerator
     private readonly List<PInvokeCallback> callbacks = new();
     private readonly PInvokeCollector _pinvokeCollector;
     private readonly bool _isLibraryMode;
+    private readonly string _runtimeIdentifier;
 
-    public PInvokeTableGenerator(Func<string, string> fixupSymbolName, LogAdapter log, bool isLibraryMode = false)
+    public PInvokeTableGenerator(Func<string, string> fixupSymbolName, LogAdapter log, bool isLibraryMode = false, string runtimeIdentifier = "browser-wasm")
     {
         Log = log;
         _fixupSymbolName = fixupSymbolName;
         _pinvokeCollector = new(log);
         _isLibraryMode = isLibraryMode;
+        _runtimeIdentifier = runtimeIdentifier;
     }
 
     public void ScanAssembly(Assembly asm)
@@ -376,7 +378,7 @@ private void EmitNativeToInterp(StreamWriter w, List<PInvokeCallback> callbacks)
                     (!cb.IsVoid ? $"{w.NewLine}    {MapType(cb.ReturnType)} result;" : "")}}
 
                     if (!(InterpEntry_T{{cb_index}})wasm_native_to_interp_ftndescs [{{cb_index}}].func) {{{
-                        (cb.IsExport && _isLibraryMode ? $"initialize_runtime();{w.NewLine}" : "")}}
+                        (cb.IsExport && _isLibraryMode && _runtimeIdentifier == "wasi-wasm" ? $"initialize_runtime();{w.NewLine}" : "")}}
                         mono_wasm_marshal_get_managed_wrapper ("{{EscapeLiteral(cb.AssemblyName)}}", "{{EscapeLiteral(cb.Namespace)}}", "{{EscapeLiteral(cb.TypeName)}}", "{{EscapeLiteral(cb.MethodName)}}", {{cb.Token}}, {{cb.Parameters.Length}});
                     }