Use mono_bind_static_method for invoking JS methods (#17942)

* Use mono_bind_static_method for invoking JS methods

Author: pranavkm

src/Components/Blazor/Blazor/src/Hosting/EntrypointInvoker.cs

@@ -22,7 +22,7 @@ public static void InvokeEntrypoint(string assemblyName, string[] args)
             {
                 var assembly = Assembly.Load(assemblyName);
                 var entrypoint = FindUnderlyingEntrypoint(assembly);
-                var @params = entrypoint.GetParameters().Length == 1 ? new object[] { args } : new object[] { };
+                var @params = entrypoint.GetParameters().Length == 1 ? new object[] { args ?? Array.Empty<string>() } : new object[] { };
                 entrypointResult = entrypoint.Invoke(null, @params);
             }
             catch (Exception syncException)

src/Components/Web.JS/dist/Release/blazor.server.js

@@ -1,19 +1,9 @@
-import { MethodHandle, System_Object, System_String, System_Array, Pointer, Platform } from '../Platform';
+import { System_Object, System_String, System_Array, Pointer, Platform } from '../Platform';
 import { getFileNameFromUrl } from '../Url';
 import { attachDebuggerHotkey, hasDebuggingEnabled } from './MonoDebugger';
 import { showErrorNotification } from '../../BootErrors';
 
-const assemblyHandleCache: { [assemblyName: string]: number } = {};
-const typeHandleCache: { [fullyQualifiedTypeName: string]: number } = {};
-const methodHandleCache: { [fullyQualifiedMethodName: string]: MethodHandle } = {};
-
-let assembly_load: (assemblyName: string) => number;
-let find_class: (assemblyHandle: number, namespace: string, className: string) => number;
-let find_method: (typeHandle: number, methodName: string, unknownArg: number) => MethodHandle;
-let invoke_method: (method: MethodHandle, target: System_Object, argsArrayPtr: number, exceptionFlagIntPtr: number) => System_Object;
-let mono_string_array_new: (length: number) => System_Array<System_String>;
 let mono_string_get_utf8: (managedString: System_String) => Mono.Utf8Ptr;
-let mono_string: (jsString: string) => System_String;
 const appBinDirName = 'appBinDir';
 const uint64HighOrderShift = Math.pow(2, 32);
 const maxSafeNumberHighPart = Math.pow(2, 21) - 1; // The high-order int32 from Number.MAX_SAFE_INTEGER
@@ -38,49 +28,16 @@ export const monoPlatform: Platform = {
     });
   },
 
-  findMethod: findMethod,
-
   callEntryPoint: function callEntryPoint(assemblyName: string) {
     // Instead of using Module.mono_call_assembly_entry_point, we have our own logic for invoking
     // the entrypoint which adds support for async main.
     // Currently we disregard the return value from the entrypoint, whether it's sync or async.
     // In the future, we might want Blazor.start to return a Promise<Promise<value>>, where the
     // outer promise reflects the startup process, and the inner one reflects the possibly-async
     // .NET entrypoint method.
-    const invokeEntrypoint = findMethod('Microsoft.AspNetCore.Blazor', 'Microsoft.AspNetCore.Blazor.Hosting', 'EntrypointInvoker', 'InvokeEntrypoint');
-    this.callMethod(invokeEntrypoint, null, [
-      this.toDotNetString(assemblyName),
-      mono_string_array_new(0) // In the future, we may have a way of supplying arg strings. For now, we always supply an empty string[].
-    ]);
-  },
-
-  callMethod: function callMethod(method: MethodHandle, target: System_Object, args: System_Object[]): System_Object {
-    if (args.length > 4) {
-      // Hopefully this restriction can be eased soon, but for now make it clear what's going on
-      throw new Error(`Currently, MonoPlatform supports passing a maximum of 4 arguments from JS to .NET. You tried to pass ${args.length}.`);
-    }
-
-    const stack = Module.stackSave();
-
-    try {
-      const argsBuffer = Module.stackAlloc(args.length);
-      const exceptionFlagManagedInt = Module.stackAlloc(4);
-      for (let i = 0; i < args.length; ++i) {
-        Module.setValue(argsBuffer + i * 4, args[i], 'i32');
-      }
-      Module.setValue(exceptionFlagManagedInt, 0, 'i32');
-
-      const res = invoke_method(method, target, argsBuffer, exceptionFlagManagedInt);
-
-      if (Module.getValue(exceptionFlagManagedInt, 'i32') !== 0) {
-        // If the exception flag is set, the returned value is exception.ToString()
-        throw new Error(monoPlatform.toJavaScriptString(<System_String>res));
-      }
-
-      return res;
-    } finally {
-      Module.stackRestore(stack);
-    }
+    const invokeEntrypoint = bindStaticMethod('Microsoft.AspNetCore.Blazor', 'Microsoft.AspNetCore.Blazor.Hosting.EntrypointInvoker', 'InvokeEntrypoint');
+    // Note we're passing in null because passing arrays is problematic until https://github.com/mono/mono/issues/18245 is resolved.
+    invokeEntrypoint(assemblyName, null);
   },
 
   toJavaScriptString: function toJavaScriptString(managedString: System_String) {
@@ -94,10 +51,6 @@ export const monoPlatform: Platform = {
     return res;
   },
 
-  toDotNetString: function toDotNetString(jsString: string): System_String {
-    return mono_string(jsString);
-  },
-
   toUint8Array: function toUint8Array(array: System_Array<any>): Uint8Array {
     const dataPtr = getArrayDataPointer(array);
     const length = Module.getValue(dataPtr, 'i32');
@@ -158,44 +111,6 @@ export const monoPlatform: Platform = {
   },
 };
 
-function findAssembly(assemblyName: string): number {
-  let assemblyHandle = assemblyHandleCache[assemblyName];
-  if (!assemblyHandle) {
-    assemblyHandle = assembly_load(assemblyName);
-    if (!assemblyHandle) {
-      throw new Error(`Could not find assembly "${assemblyName}"`);
-    }
-    assemblyHandleCache[assemblyName] = assemblyHandle;
-  }
-  return assemblyHandle;
-}
-
-function findType(assemblyName: string, namespace: string, className: string): number {
-  const fullyQualifiedTypeName = `[${assemblyName}]${namespace}.${className}`;
-  let typeHandle = typeHandleCache[fullyQualifiedTypeName];
-  if (!typeHandle) {
-    typeHandle = find_class(findAssembly(assemblyName), namespace, className);
-    if (!typeHandle) {
-      throw new Error(`Could not find type "${className}" in namespace "${namespace}" in assembly "${assemblyName}"`);
-    }
-    typeHandleCache[fullyQualifiedTypeName] = typeHandle;
-  }
-  return typeHandle;
-}
-
-function findMethod(assemblyName: string, namespace: string, className: string, methodName: string): MethodHandle {
-  const fullyQualifiedMethodName = `[${assemblyName}]${namespace}.${className}::${methodName}`;
-  let methodHandle = methodHandleCache[fullyQualifiedMethodName];
-  if (!methodHandle) {
-    methodHandle = find_method(findType(assemblyName, namespace, className), methodName, -1);
-    if (!methodHandle) {
-      throw new Error(`Could not find method "${methodName}" on type "${namespace}.${className}"`);
-    }
-    methodHandleCache[fullyQualifiedMethodName] = methodHandle;
-  }
-  return methodHandle;
-}
-
 function addScriptTagsToDocument() {
   const browserSupportsNativeWebAssembly = typeof WebAssembly !== 'undefined' && WebAssembly.validate;
   if (!browserSupportsNativeWebAssembly) {
@@ -254,26 +169,8 @@ function createEmscriptenModuleInstance(loadAssemblyUrls: string[], onReady: ()
       'number',
       'number',
     ]);
-    assembly_load = Module.cwrap('mono_wasm_assembly_load', 'number', ['string']);
-    find_class = Module.cwrap('mono_wasm_assembly_find_class', 'number', [
-      'number',
-      'string',
-      'string',
-    ]);
-    find_method = Module.cwrap('mono_wasm_assembly_find_method', 'number', [
-      'number',
-      'string',
-      'number',
-    ]);
-    invoke_method = Module.cwrap('mono_wasm_invoke_method', 'number', [
-      'number',
-      'number',
-      'number',
-    ]);
 
     mono_string_get_utf8 = Module.cwrap('mono_wasm_string_get_utf8', 'number', ['number']);
-    mono_string = Module.cwrap('mono_wasm_string_from_js', 'number', ['string']);
-    mono_string_array_new = Module.cwrap('mono_wasm_string_array_new', 'number', ['number']);
 
     MONO.loaded_files = [];
 
@@ -346,10 +243,16 @@ function getArrayDataPointer<T>(array: System_Array<T>): number {
   return <number><any>array + 12; // First byte from here is length, then following bytes are entries
 }
 
+function bindStaticMethod(assembly: string, typeName: string, method: string) : (...args: any[]) => any {
+  // Fully qualified name looks like this: "[debugger-test] Math:IntAdd"
+  const fqn = `[${assembly}] ${typeName}:${method}`;
+  return Module.mono_bind_static_method(fqn);
+}
+
 function attachInteropInvoker(): void {
-  const dotNetDispatcherInvokeMethodHandle = findMethod('Mono.WebAssembly.Interop', 'Mono.WebAssembly.Interop', 'MonoWebAssemblyJSRuntime', 'InvokeDotNet');
-  const dotNetDispatcherBeginInvokeMethodHandle = findMethod('Mono.WebAssembly.Interop', 'Mono.WebAssembly.Interop', 'MonoWebAssemblyJSRuntime', 'BeginInvokeDotNet');
-  const dotNetDispatcherEndInvokeJSMethodHandle = findMethod('Mono.WebAssembly.Interop', 'Mono.WebAssembly.Interop', 'MonoWebAssemblyJSRuntime', 'EndInvokeJS');
+  const dotNetDispatcherInvokeMethodHandle =  bindStaticMethod('Mono.WebAssembly.Interop', 'Mono.WebAssembly.Interop.MonoWebAssemblyJSRuntime', 'InvokeDotNet');
+  const dotNetDispatcherBeginInvokeMethodHandle = bindStaticMethod('Mono.WebAssembly.Interop', 'Mono.WebAssembly.Interop.MonoWebAssemblyJSRuntime', 'BeginInvokeDotNet');
+  const dotNetDispatcherEndInvokeJSMethodHandle = bindStaticMethod('Mono.WebAssembly.Interop', 'Mono.WebAssembly.Interop.MonoWebAssemblyJSRuntime', 'EndInvokeJS');
 
   DotNet.attachDispatcher({
     beginInvokeDotNetFromJS: (callId: number, assemblyName: string | null, methodIdentifier: string, dotNetObjectId: any | null, argsJson: string): void => {
@@ -362,30 +265,25 @@ function attachInteropInvoker(): void {
         ? dotNetObjectId.toString()
         : assemblyName;
 
-      monoPlatform.callMethod(dotNetDispatcherBeginInvokeMethodHandle, null, [
-        callId ? monoPlatform.toDotNetString(callId.toString()) : null,
-        monoPlatform.toDotNetString(assemblyNameOrDotNetObjectId),
-        monoPlatform.toDotNetString(methodIdentifier),
-        monoPlatform.toDotNetString(argsJson),
-      ]);
+        dotNetDispatcherBeginInvokeMethodHandle(
+          callId ? callId.toString() : null,
+          assemblyNameOrDotNetObjectId,
+          methodIdentifier,
+          argsJson,
+        );
     },
     endInvokeJSFromDotNet: (asyncHandle, succeeded, serializedArgs): void => {
-      monoPlatform.callMethod(
-        dotNetDispatcherEndInvokeJSMethodHandle,
-        null,
-        [monoPlatform.toDotNetString(serializedArgs)]
+      dotNetDispatcherEndInvokeJSMethodHandle(
+        serializedArgs
       );
     },
     invokeDotNetFromJS: (assemblyName, methodIdentifier, dotNetObjectId, argsJson) => {
-      const resultJsonStringPtr = monoPlatform.callMethod(dotNetDispatcherInvokeMethodHandle, null, [
-        assemblyName ? monoPlatform.toDotNetString(assemblyName) : null,
-        monoPlatform.toDotNetString(methodIdentifier),
-        dotNetObjectId ? monoPlatform.toDotNetString(dotNetObjectId.toString()) : null,
-        monoPlatform.toDotNetString(argsJson),
-      ]) as System_String;
-      return resultJsonStringPtr
-        ? monoPlatform.toJavaScriptString(resultJsonStringPtr)
-        : null;
+      return dotNetDispatcherInvokeMethodHandle(
+        assemblyName ? assemblyName : null,
+        methodIdentifier,
+        dotNetObjectId ? dotNetObjectId.toString() : null,
+        argsJson,
+      ) as string;
     },
   });
 }

src/Components/Web.JS/dist/Release/blazor.webassembly.js

@@ -10,7 +10,7 @@ declare namespace Module {
   function FS_createPath(parent, path, canRead, canWrite);
   function FS_createDataFile(parent, name, data, canRead, canWrite, canOwn);
 
-  function mono_call_assembly_entry_point(assemblyName: string, args: any[]): any;
+  function mono_bind_static_method(fqn: string): BoundStaticMethod;
 }
 
 // Emscripten declares these globals
@@ -28,3 +28,7 @@ declare namespace MONO {
   var mono_wasm_runtime_is_ready: boolean;
   function mono_wasm_setenv (name: string, value: string): void;
 }
+
+// mono_bind_static_method allows arbitrary JS data types to be sent over the wire. However we are
+// artifically limiting it to a subset of types that we actually use.
+declare type BoundStaticMethod = (...args: (string | number | null)[]) => (string | number | null);

src/Components/Web.JS/src/Platform/Mono/MonoPlatform.ts

@@ -2,12 +2,8 @@ export interface Platform {
   start(loadAssemblyUrls: string[]): Promise<void>;
 
   callEntryPoint(assemblyName: string): void;
-  findMethod(assemblyName: string, namespace: string, className: string, methodName: string): MethodHandle;
-  callMethod(method: MethodHandle, target: System_Object | null, args: (System_Object | null)[]): System_Object;
 
   toJavaScriptString(dotNetString: System_String): string;
-  toDotNetString(javaScriptString: string): System_String;
-
   toUint8Array(array: System_Array<any>): Uint8Array;
 
   getArrayLength(array: System_Array<any>): number;