Initial debugger support

samples/MonoSanity/wwwroot/index.html

@@ -68,7 +68,7 @@
   <script type="blazor-boot"></script>
   <script src="loader.js"></script>
   <script>
-    initMono(['/_framework/_bin/MonoSanityClient.dll'], function () {
+    initMono(['_framework/_bin/MonoSanityClient.dll', '_framework/_bin/MonoSanityClient.pdb'], function () {
       var buttons = document.getElementsByTagName('button');
       for (var i = 0; i < buttons.length; i++) {
         buttons[i].disabled = false;

samples/MonoSanity/wwwroot/loader.js

@@ -30,8 +30,9 @@
         preloadAssemblies(loadAssemblyUrls);
       }],
       postRun: [function () {
-        var load_runtime = Module.cwrap('mono_wasm_load_runtime', null, ['string']);
+        var load_runtime = Module.cwrap('mono_wasm_load_runtime', null, ['string', 'number']);
-        load_runtime('appBinDir');
+        load_runtime('appBinDir', 1);
+        MONO.mono_wasm_runtime_is_ready = true;
         onReadyCallback();
       }]
     };
@@ -85,13 +86,22 @@
       .concat(loadBclAssemblies.map(function (name) { return '_framework/_bin/' + name + '.dll'; }));
 
     Module.FS_createPath('/', 'appBinDir', true, true);
+
+    MONO.loaded_files = []; // Used by debugger
     allAssemblyUrls.forEach(function (url) {
-      FS.createPreloadedFile('appBinDir', getAssemblyNameFromUrl(url) + '.dll', url, true, false, null, function onError(err) {
+      FS.createPreloadedFile('appBinDir', getFileNameFromUrl(url), url, true, false,
-        throw err;
+        /* success */ function() { MONO.loaded_files.push(toAbsoluteUrl(url)); },
-      });
+        /* failure */ function onError(err) { throw err; }
+      );
     });
   }
 
+  var anchorTagForAbsoluteUrlConversions = document.createElement('a');
+  function toAbsoluteUrl(possiblyRelativeUrl) {
+    anchorTagForAbsoluteUrlConversions.href = possiblyRelativeUrl;
+    return anchorTagForAbsoluteUrlConversions.href;
+  }
+
   function asyncLoad(url, onload, onerror) {
     var xhr = new XMLHttpRequest;
     xhr.open('GET', url, /* async: */ true);
@@ -161,11 +171,11 @@
     document.body.appendChild(scriptElem);
   }
 
-  function getAssemblyNameFromUrl(url) {
+  function getFileNameFromUrl(url) {
     var lastSegment = url.substring(url.lastIndexOf('/') + 1);
     var queryStringStartPos = lastSegment.indexOf('?');
     var filename = queryStringStartPos < 0 ? lastSegment : lastSegment.substring(0, queryStringStartPos);
-    return filename.replace(/\.dll$/, '');
+    return filename;
   }
 
 })();

samples/MonoSanityClient/MonoSanityClient.csproj

@@ -1,9 +1,12 @@
-<Project Sdk="Microsoft.NET.Sdk.Razor" TreatAsLocalProperty="BlazorLinkOnBuild">
+<Project Sdk="Microsoft.NET.Sdk.Razor" TreatAsLocalProperty="BlazorLinkOnBuild">
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
     <IsPackable>false</IsPackable>
     <BlazorLinkOnBuild>false</BlazorLinkOnBuild>
+
+    <!-- loader.js is hard-coded to assume it can load .pdbs regardless of Debug/Release configuration -->
+    <BlazorEnableDebugging>true</BlazorEnableDebugging>
   </PropertyGroup>
 
   <!-- Local alternative to <PackageReference Include="Microsoft.AspNetCore.Blazor.Build" /> -->

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Boot.ts

@@ -1,6 +1,6 @@
 import '../../Microsoft.JSInterop/JavaScriptRuntime/src/Microsoft.JSInterop';
 import { platform } from './Environment';
-import { getAssemblyNameFromUrl } from './Platform/DotNet';
+import { getAssemblyNameFromUrl } from './Platform/Url';
 import './GlobalExports';
 
 async function boot() {

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Platform/DotNet.ts

@@ -1,6 +0,0 @@
-export function getAssemblyNameFromUrl(url: string) {
-  const lastSegment = url.substring(url.lastIndexOf('/') + 1);
-  const queryStringStartPos = lastSegment.indexOf('?');
-  const filename = queryStringStartPos < 0 ? lastSegment : lastSegment.substring(0, queryStringStartPos);
-  return filename.replace(/\.dll$/, '');
-}

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Platform/Mono/MonoDebugger.ts

@@ -0,0 +1,50 @@
+import { getAssemblyNameFromUrl, getFileNameFromUrl } from '../Url';
+
+const currentBrowserIsChrome = (window as any).chrome
+  && navigator.userAgent.indexOf('Edge') < 0; // Edge pretends to be Chrome
+
+let hasReferencedPdbs = false;
+
+export function hasDebuggingEnabled() {
+  return hasReferencedPdbs && currentBrowserIsChrome;
+}
+
+export function attachDebuggerHotkey(loadAssemblyUrls: string[]) {
+  hasReferencedPdbs = loadAssemblyUrls
+    .some(url => /\.pdb$/.test(getFileNameFromUrl(url)));
+
+  // Use the combination shift+alt+D because it isn't used by the major browsers
+  // for anything else by default
+  const altKeyName = navigator.platform.match(/^Mac/i) ? 'Cmd' : 'Alt';
+  if (hasDebuggingEnabled()) {
+    console.info(`Debugging hotkey: Shift+${altKeyName}+D (when application has focus)`);
+  }
+
+  // Even if debugging isn't enabled, we register the hotkey so we can report why it's not enabled
+  document.addEventListener('keydown', evt => {
+    if (evt.shiftKey && (evt.metaKey || evt.altKey) && evt.code === 'KeyD') {
+      if (!hasReferencedPdbs) {
+        console.error('Cannot start debugging, because the application was not compiled with debugging enabled.');
+      } else if (!currentBrowserIsChrome) {
+        console.error('Currently, only Chrome is supported for debugging.');
+      } else {
+        launchDebugger();
+      }
+    }
+  });
+}
+
+function launchDebugger() {
+  // The noopener flag is essential, because otherwise Chrome tracks the association with the
+  // parent tab, and then when the parent tab pauses in the debugger, the child tab does so
+  // too (even if it's since navigated to a different page). This means that the debugger
+  // itself freezes, and not just the page being debugged.
+  //
+  // We have to construct a link element and simulate a click on it, because the more obvious
+  // window.open(..., 'noopener') always opens a new window instead of a new tab.
+  const link = document.createElement('a');
+  link.href = `_framework/debug?url=${encodeURIComponent(location.href)}`;
+  link.target = '_blank';
+  link.rel = 'noopener noreferrer';
+  link.click();
+}

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Platform/Mono/MonoPlatform.ts

@@ -1,5 +1,6 @@
 import { MethodHandle, System_Object, System_String, System_Array, Pointer, Platform } from '../Platform';
-import { getAssemblyNameFromUrl } from '../DotNet';
+import { getAssemblyNameFromUrl, getFileNameFromUrl } from '../Url';
+import { attachDebuggerHotkey, hasDebuggingEnabled } from './MonoDebugger';
 
 const assemblyHandleCache: { [assemblyName: string]: number } = {};
 const typeHandleCache: { [fullyQualifiedTypeName: string]: number } = {};
@@ -11,14 +12,16 @@ let find_method: (typeHandle: number, methodName: string, unknownArg: number) =>
 let invoke_method: (method: MethodHandle, target: System_Object, argsArrayPtr: number, exceptionFlagIntPtr: number) => System_Object;
 let mono_string_get_utf8: (managedString: System_String) => Mono.Utf8Ptr;
 let mono_string: (jsString: string) => System_String;
+const appBinDirName = 'appBinDir';
 
 export const monoPlatform: Platform = {
   start: function start(loadAssemblyUrls: string[]) {
     return new Promise<void>((resolve, reject) => {
+      attachDebuggerHotkey(loadAssemblyUrls);
+
       // mono.js assumes the existence of this
       window['Browser'] = {
-        init: () => { },
+        init: () => { }
-        asyncLoad: asyncLoad
       };
       // Emscripten works by expecting the module config to be a global
       window['Module'] = createEmscriptenModuleInstance(loadAssemblyUrls, resolve, reject);
@@ -192,8 +195,9 @@ function createEmscriptenModuleInstance(loadAssemblyUrls: string[], onReady: ()
   const module = {} as typeof Module;
   const wasmBinaryFile = '_framework/wasm/mono.wasm';
   const asmjsCodeFile = '_framework/asmjs/mono.asm.js';
+  const suppressMessages = ['DEBUGGING ENABLED'];
 
-  module.print = line => console.log(`WASM: ${line}`);
+  module.print = line => (suppressMessages.indexOf(line) < 0 && console.log(`WASM: ${line}`));
   module.printErr = line => console.error(`WASM: ${line}`);
   module.preRun = [];
   module.postRun = [];
@@ -216,14 +220,39 @@ function createEmscriptenModuleInstance(loadAssemblyUrls: string[], onReady: ()
     mono_string_get_utf8 = Module.cwrap('mono_wasm_string_get_utf8', 'number', ['number']);
     mono_string = Module.cwrap('mono_wasm_string_from_js', 'number', ['string']);
 
-    Module.FS_createPath('/', 'appBinDir', true, true);
+    Module.FS_createPath('/', appBinDirName, true, true);
-    loadAssemblyUrls.forEach(url =>
+    MONO.loaded_files = [];
-      FS.createPreloadedFile('appBinDir', `${getAssemblyNameFromUrl(url)}.dll`, url, true, false, undefined, onError));
+
+    loadAssemblyUrls.forEach(url => {
+      const filename = getFileNameFromUrl(url);
+      const runDependencyId = `blazor:${filename}`;
+      addRunDependency(runDependencyId);
+      asyncLoad(url).then(
+        data => {
+          Module.FS_createDataFile(appBinDirName, filename, data, true, false, false);
+          MONO.loaded_files.push(toAbsoluteUrl(url));
+          removeRunDependency(runDependencyId);
+        },
+        errorInfo => {
+          // If it's a 404 on a .pdb, we don't want to block the app from starting up.
+          // We'll just skip that file and continue (though the 404 is logged in the console).
+          // This happens if you build a Debug build but then run in Production environment.
+          const isPdb404 = errorInfo instanceof XMLHttpRequest
+            && errorInfo.status === 404
+            && filename.match(/\.pdb$/);
+          if (!isPdb404) {
+            onError(errorInfo);
+          }
+          removeRunDependency(runDependencyId);
+        }
+      );
+    });
   });
 
   module.postRun.push(() => {
-    const load_runtime = Module.cwrap('mono_wasm_load_runtime', null, ['string']);
+    const load_runtime = Module.cwrap('mono_wasm_load_runtime', null, ['string', 'number']);
-    load_runtime('appBinDir');
+    load_runtime(appBinDirName, hasDebuggingEnabled() ? 1 : 0);
+    MONO.mono_wasm_runtime_is_ready = true;
     attachInteropInvoker();
     onReady();
   });
@@ -231,20 +260,28 @@ function createEmscriptenModuleInstance(loadAssemblyUrls: string[], onReady: ()
   return module;
 }
 
-function asyncLoad(url, onload, onerror) {
+const anchorTagForAbsoluteUrlConversions = document.createElement('a');
-  var xhr = new XMLHttpRequest;
+function toAbsoluteUrl(possiblyRelativeUrl: string) {
-  xhr.open('GET', url, /* async: */ true);
+  anchorTagForAbsoluteUrlConversions.href = possiblyRelativeUrl;
-  xhr.responseType = 'arraybuffer';
+  return anchorTagForAbsoluteUrlConversions.href;
-  xhr.onload = function xhr_onload() {
+}
-    if (xhr.status == 200 || xhr.status == 0 && xhr.response) {
+
-      var asm = new Uint8Array(xhr.response);
+function asyncLoad(url) {
-      onload(asm);
+  return new Promise((resolve, reject) => {
-    } else {
+    var xhr = new XMLHttpRequest;
-      onerror(xhr);
+    xhr.open('GET', url, /* async: */ true);
-    }
+    xhr.responseType = 'arraybuffer';
-  };
+    xhr.onload = function xhr_onload() {
-  xhr.onerror = onerror;
+      if (xhr.status == 200 || xhr.status == 0 && xhr.response) {
-  xhr.send(null);
+        var asm = new Uint8Array(xhr.response);
+        resolve(asm);
+      } else {
+        reject(xhr);
+      }
+    };
+    xhr.onerror = reject;
+    xhr.send(null);
+  });
 }
 
 function getArrayDataPointer<T>(array: System_Array<T>): number {

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Platform/Mono/MonoTypes.d.ts

@@ -1,4 +1,4 @@
-declare namespace Module {
+declare namespace Module {
   function UTF8ToString(utf8: Mono.Utf8Ptr): string;
   var preloadPlugins: any[];
 
@@ -11,7 +11,17 @@
   function FS_createDataFile(parent, name, data, canRead, canWrite, canOwn);
 }
 
+// Emscripten declares these globals
+declare const addRunDependency: any;
+declare const removeRunDependency: any;
+
 declare namespace Mono {
   interface Utf8Ptr { Utf8Ptr__DO_NOT_IMPLEMENT: any }
   interface StackSaveHandle { StackSaveHandle__DO_NOT_IMPLEMENT: any }
 }
+
+// Mono uses this global to hang various debugging-related items on
+declare namespace MONO {
+  var loaded_files: string[];
+  var mono_wasm_runtime_is_ready: boolean;
+}

src/Microsoft.AspNetCore.Blazor.Browser.JS/src/Platform/Url.ts

@@ -0,0 +1,11 @@
+export function getFileNameFromUrl(url: string) {
+  // This could also be called "get last path segment from URL", but the primary
+  // use case is to extract things that look like filenames
+  const lastSegment = url.substring(url.lastIndexOf('/') + 1);
+  const queryStringStartPos = lastSegment.indexOf('?');
+  return queryStringStartPos < 0 ? lastSegment : lastSegment.substring(0, queryStringStartPos);
+}
+
+export function getAssemblyNameFromUrl(url: string) {
+  return getFileNameFromUrl(url).replace(/\.dll$/, '');
+}

src/Microsoft.AspNetCore.Blazor.Build/Core/RuntimeDependenciesResolver.cs

@@ -1,6 +1,7 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
@@ -45,7 +46,14 @@ namespace Microsoft.AspNetCore.Blazor.Build
             assemblyResolutionContext.ResolveAssemblies();
 
             var paths = assemblyResolutionContext.Results.Select(r => r.Path);
-            return paths;
+            return paths.Concat(FindPdbs(paths));
+        }
+
+        private static IEnumerable<string> FindPdbs(IEnumerable<string> dllPaths)
+        {
+            return dllPaths
+                .Select(path => Path.ChangeExtension(path, "pdb"))
+                .Where(path => File.Exists(path));
         }
 
         public class AssemblyResolutionContext

src/Microsoft.AspNetCore.Blazor.Build/targets/All.props

@@ -1,12 +1,15 @@
-<Project>
+<Project>
   <Import Project="Blazor.MonoRuntime.props" />
 
   <PropertyGroup>
     <DefaultWebContentItemExcludes>$(DefaultWebContentItemExcludes);wwwroot\**</DefaultWebContentItemExcludes>
 
     <!-- By default, enable auto rebuilds for debug builds. Note that the server will not enable it in production environments regardless. -->
-    <BlazorRebuildOnFileChange Condition="'$(Configuration)' == 'Debug'">true</BlazorRebuildOnFileChange>
+    <BlazorRebuildOnFileChange Condition="'$(Configuration)' == 'Debug' AND '$(BlazorRebuildOnFileChange)' == ''">true</BlazorRebuildOnFileChange>
-    
+
+    <!-- By default, enable debugging for debug builds. -->
+    <BlazorEnableDebugging Condition="'$(Configuration)' == 'Debug' AND '$(BlazorEnableDebugging)' == ''">true</BlazorEnableDebugging>
+      
     <!-- When using IISExpress with a standalone app, there's no point restarting IISExpress after build. It slows things unnecessarily and breaks in-flight HTTP requests. -->
     <NoRestartServerOnBuild>true</NoRestartServerOnBuild>
   </PropertyGroup>

src/Microsoft.AspNetCore.Blazor.Build/targets/All.targets

@@ -24,6 +24,7 @@
     <WriteLinesToFile File="$(BlazorMetadataFilePath)" Lines="$(MSBuildProjectFullPath)" Overwrite="true" Encoding="Unicode"/>
     <WriteLinesToFile File="$(BlazorMetadataFilePath)" Lines="$(OutDir)$(AssemblyName).dll" Overwrite="false" Encoding="Unicode"/>
     <WriteLinesToFile File="$(BlazorMetadataFilePath)" Condition="'$(BlazorRebuildOnFileChange)'=='true'" Lines="autorebuild:true" Overwrite="false" Encoding="Unicode"/>
+    <WriteLinesToFile File="$(BlazorMetadataFilePath)" Condition="'$(BlazorEnableDebugging)'=='true'" Lines="debug:true" Overwrite="false" Encoding="Unicode"/>
     <ItemGroup>
       <ContentWithTargetPath Include="$(BlazorMetadataFilePath)" TargetPath="$(BlazorMetadataFileName)" CopyToOutputDirectory="PreserveNewest" />
     </ItemGroup>

src/Microsoft.AspNetCore.Blazor.Build/targets/Blazor.MonoRuntime.props

@@ -11,7 +11,7 @@
 
   <PropertyGroup Label="Blazor build outputs">
     <MonoLinkerI18NAssemblies>none</MonoLinkerI18NAssemblies> <!-- See Mono linker docs - allows comma-separated values from: none,all,cjk,mideast,other,rare,west -->
-    <AdditionalMonoLinkerOptions>-c link -u link -t --verbose </AdditionalMonoLinkerOptions>
+    <AdditionalMonoLinkerOptions>-c link -u link -b true -t --verbose </AdditionalMonoLinkerOptions>
     <BaseBlazorDistPath>dist/</BaseBlazorDistPath>
     <BaseBlazorPackageContentOutputPath>$(BaseBlazorDistPath)_content/</BaseBlazorPackageContentOutputPath>
     <BaseBlazorRuntimeOutputPath>$(BaseBlazorDistPath)_framework/</BaseBlazorRuntimeOutputPath>

src/Microsoft.AspNetCore.Blazor.Build/targets/Blazor.MonoRuntime.targets

@@ -272,6 +272,7 @@
       <_BlazorCommonInput Include="@(IntermediateAssembly)" />
       <_BlazorCommonInput Include="@(_BlazorDependencyInput)" />
       <_BlazorCommonInput Include="$(_BlazorShouldLinkApplicationAssemblies)" />
+      <_BlazorCommonInput Include="$(BlazorEnableDebugging)" />
       <_BlazorLinkingOption Condition="'$(_BlazorShouldLinkApplicationAssemblies)' == ''" Include="false" />
       <_BlazorLinkingOption Condition="'$(_BlazorShouldLinkApplicationAssemblies)' != ''" Include="true" />
     </ItemGroup>
@@ -340,11 +341,15 @@
     </ReadLinesFromFile>
 
     <ItemGroup>
-      <BlazorItemOutput Include="@(_OptimizedFiles)">
+      <BlazorItemOutput Include="@(_OptimizedFiles->WithMetadataValue('Extension','.dll'))">
         <TargetOutputPath>$(BlazorRuntimeBinOutputPath)%(FileName)%(Extension)</TargetOutputPath>
         <Type>Assembly</Type>
         <PrimaryOutput Condition="'%(FileName)' == @(IntermediateAssembly->'%(FileName)')">true</PrimaryOutput>
       </BlazorItemOutput>
+      <BlazorItemOutput Include="@(_OptimizedFiles->WithMetadataValue('Extension','.pdb'))">
+        <TargetOutputPath>$(BlazorRuntimeBinOutputPath)%(FileName)%(Extension)</TargetOutputPath>
+        <Type>Pdb</Type>
+      </BlazorItemOutput>
       <FileWrites Include="@(BlazorItemOutput->WithMetadataValue('Type','Assembly')->'%(TargetOutputPath)')" />
     </ItemGroup>
 
@@ -443,6 +448,7 @@
     <!-- Collect the contents of /obj/<<configuration>>/<<targetframework>>/blazor/blazor/linker/ -->
     <ItemGroup>
       <_BlazorLinkerOutput Include="$(BlazorIntermediateLinkerOutputPath)*.dll" />
+      <_BlazorLinkerOutput Include="$(BlazorIntermediateLinkerOutputPath)*.pdb" />
     </ItemGroup>
 
     <!--
@@ -497,14 +503,17 @@
     -->
 
     <ItemGroup>
-      <BlazorItemOutput Include="@(_IntermediateResolvedRuntimeDependencies)">
+      <BlazorItemOutput Include="@(_IntermediateResolvedRuntimeDependencies->WithMetadataValue('Extension','.dll'))">
         <TargetOutputPath>$(BlazorRuntimeBinOutputPath)%(FileName)%(Extension)</TargetOutputPath>
         <Type>Assembly</Type>
         <PrimaryOutput Condition="'%(FileName)' == @(IntermediateAssembly->'%(FileName)')">true</PrimaryOutput>
       </BlazorItemOutput>
+      <BlazorItemOutput Include="@(_IntermediateResolvedRuntimeDependencies->WithMetadataValue('Extension','.pdb'))">
+        <TargetOutputPath>$(BlazorRuntimeBinOutputPath)%(FileName)%(Extension)</TargetOutputPath>
+        <Type>Pdb</Type>
+      </BlazorItemOutput>
       <FileWrites Include="@(BlazorItemOutput->WithMetadataValue('Type','Assembly')->'%(TargetOutputPath)')" />
     </ItemGroup>
-
   </Target>
 
   <Target
@@ -583,8 +592,11 @@
   <Target Name="_ResolveBlazorIndexHtmlInputs">
     <ItemGroup>
       <BlazorIndexHtmlInput Include="$(BlazorIndexHtml)" />
+      <BlazorIndexHtmlInput Include="$(Configuration)" />
       <BlazorIndexHtmlInput Include="@(BlazorItemOutput->WithMetadataValue('Type','Assembly')->'%(FullPath)')" />
+      <BlazorIndexHtmlInput Include="@(BlazorItemOutput->WithMetadataValue('Type','Pdb')->'%(FullPath)')" />
       <BlazorIndexHtmlInput Include="@(_BlazorLinkingOption)" />
+      <BlazorIndexHtmlInput Include="$(BlazorEnableDebugging)" />
     </ItemGroup>
 
     <WriteLinesToFile
@@ -607,6 +619,7 @@
     <ItemGroup>
       <_UnlinkedAppReferencesPaths Include="@(_BlazorDependencyInput)" />
       <_AppReferences Include="@(BlazorItemOutput->WithMetadataValue('Type','Assembly')->WithMetadataValue('PrimaryOutput','')->'%(FileName)%(Extension)')" />
+      <_AppReferences Include="@(BlazorItemOutput->WithMetadataValue('Type','Pdb')->'%(FileName)%(Extension)')" Condition="'$(BlazorEnableDebugging)' == 'true'" />
     </ItemGroup>
     <PropertyGroup>
       <_LinkerEnabledFlag Condition="'$(_BlazorShouldLinkApplicationAssemblies)' != ''">--linker-enabled</_LinkerEnabledFlag>

src/Microsoft.AspNetCore.Blazor.Build/targets/BuiltInBclLinkerDescriptor.xml

@@ -8,20 +8,6 @@
     <!-- Preserve all methods on WasmRuntime, because these are called by JS-side code
     to implement timers. Fixes https://github.com/aspnet/Blazor/issues/239 -->
     <type fullname="System.Threading.WasmRuntime" />
-
-      <!-- Mono redirects certain string constructor calls to CreateString internally, so preserve them -->
-      <type fullname="System.String">
-          <method signature="System.String CreateString(System.Char,System.Int32)" />
-          <method signature="System.String CreateString(System.Char[])" />
-          <method signature="System.String CreateString(System.Char[],System.Int32,System.Int32)" />
-          <method signature="System.String CreateString(System.Char*)" />
-          <method signature="System.String CreateString(System.Char*,System.Int32,System.Int32)" />
-          <method signature="System.String CreateString(System.Byte*)" />
-          <method signature="System.String CreateString(System.Byte*,System.Int32,System.Int32)" />
-          <method signature="System.String CreateString(System.Byte*,System.Int32,System.Int32,System.Text.Encoding)" />
-          <method signature="System.String CreateString(System.SByte*)" />
-          <method signature="System.String CreateString(System.SByte*,System.Int32,System.Int32,System.Text.Encoding)" />
-      </type>
   </assembly>
 
 </linker>

src/Microsoft.AspNetCore.Blazor.Server/AutoRebuild/AutoRebuildExtensions.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.AspNetCore.Blazor.Server;
@@ -27,7 +27,7 @@ namespace Microsoft.AspNetCore.Builder
         // way to remove middleware once it's registered.
         private static List<object> _uncollectableWatchers = new List<object>();
 
-        public static void UseHostedAutoRebuild(this IApplicationBuilder appBuilder, BlazorConfig config, string hostAppContentRootPath)
+        public static void UseHostedAutoRebuild(this IApplicationBuilder app, BlazorConfig config, string hostAppContentRootPath)
         {
             var isFirstFileWrite = true;
             WatchFileSystem(config, () =>
@@ -51,7 +51,7 @@ namespace Microsoft.AspNetCore.Builder
                     catch (Exception ex)
                     {
                         // If we don't have permission to write these files, autorebuild will not be enabled
-                        var loggerFactory = appBuilder.ApplicationServices.GetRequiredService<ILoggerFactory>();
+                        var loggerFactory = app.ApplicationServices.GetRequiredService<ILoggerFactory>();
                         var logger = loggerFactory.CreateLogger(typeof (AutoRebuildExtensions));
                         logger?.LogWarning(ex,
                             "Cannot autorebuild because there was an error when writing to a file in '{0}'.",
@@ -63,7 +63,7 @@ namespace Microsoft.AspNetCore.Builder
             });
         }
 
-        public static void UseDevServerAutoRebuild(this IApplicationBuilder appBuilder, BlazorConfig config)
+        public static void UseDevServerAutoRebuild(this IApplicationBuilder app, BlazorConfig config)
         {
             // Currently this only supports VS for Windows. Later on we can add
             // an IRebuildService implementation for VS for Mac, etc.
@@ -87,7 +87,7 @@ namespace Microsoft.AspNetCore.Builder
                 buildToken = new RebuildToken(DateTime.Now);
             });
 
-            appBuilder.Use(async (context, next) =>
+            app.Use(async (context, next) =>
             {
                 try
                 {

src/Microsoft.AspNetCore.Blazor.Server/BlazorAppBuilderExtensions.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.AspNetCore.Http;
@@ -23,12 +23,12 @@ namespace Microsoft.AspNetCore.Builder
         /// Configures the middleware pipeline to work with Blazor.
         /// </summary>
         /// <typeparam name="TProgram">Any type from the client app project. This is used to identify the client app assembly.</typeparam>
-        /// <param name="applicationBuilder"></param>
+        /// <param name="app"></param>
         public static void UseBlazor<TProgram>(
-            this IApplicationBuilder applicationBuilder)
+            this IApplicationBuilder app)
         {
             var clientAssemblyInServerBinDir = typeof(TProgram).Assembly;
-            applicationBuilder.UseBlazor(new BlazorOptions
+            app.UseBlazor(new BlazorOptions
             {
                 ClientAssemblyPath = clientAssemblyInServerBinDir.Location,
             });
@@ -37,21 +37,21 @@ namespace Microsoft.AspNetCore.Builder
         /// <summary>
         /// Configures the middleware pipeline to work with Blazor.
         /// </summary>
-        /// <param name="applicationBuilder"></param>
+        /// <param name="app"></param>
         /// <param name="options"></param>
         public static void UseBlazor(
-            this IApplicationBuilder applicationBuilder,
+            this IApplicationBuilder app,
             BlazorOptions options)
         {
             // TODO: Make the .blazor.config file contents sane
             // Currently the items in it are bizarre and don't relate to their purpose,
             // hence all the path manipulation here. We shouldn't be hardcoding 'dist' here either.
-            var env = (IHostingEnvironment)applicationBuilder.ApplicationServices.GetService(typeof(IHostingEnvironment));
+            var env = (IHostingEnvironment)app.ApplicationServices.GetService(typeof(IHostingEnvironment));
             var config = BlazorConfig.Read(options.ClientAssemblyPath);
             var distDirStaticFiles = new StaticFileOptions
             {
                 FileProvider = new PhysicalFileProvider(config.DistPath),
-                ContentTypeProvider = CreateContentTypeProvider(),
+                ContentTypeProvider = CreateContentTypeProvider(config.EnableDebugging),
                 OnPrepareResponse = SetCacheHeaders
             };
 
@@ -59,16 +59,16 @@ namespace Microsoft.AspNetCore.Builder
             {
                 if (env.ApplicationName.Equals(DevServerApplicationName, StringComparison.OrdinalIgnoreCase))
                 {
-                    applicationBuilder.UseDevServerAutoRebuild(config);
+                    app.UseDevServerAutoRebuild(config);
                 }
                 else
                 {
-                    applicationBuilder.UseHostedAutoRebuild(config, env.ContentRootPath);
+                    app.UseHostedAutoRebuild(config, env.ContentRootPath);
                 }
             }
 
             // First, match the request against files in the client app dist directory
-            applicationBuilder.UseStaticFiles(distDirStaticFiles);
+            app.UseStaticFiles(distDirStaticFiles);
 
             // Next, match the request against static files in wwwroot
             if (!string.IsNullOrEmpty(config.WebRootPath))
@@ -77,16 +77,22 @@ namespace Microsoft.AspNetCore.Builder
                 // (and don't require them to be copied into dist).
                 // TODO: When publishing is implemented, have config.WebRootPath set
                 // to null so that it only serves files that were copied to dist
-                applicationBuilder.UseStaticFiles(new StaticFileOptions
+                app.UseStaticFiles(new StaticFileOptions
                 {
                     FileProvider = new PhysicalFileProvider(config.WebRootPath),
                     OnPrepareResponse = SetCacheHeaders
                 });
             }
 
+            // Accept debugger connections
+            if (config.EnableDebugging)
+            {
+                app.UseMonoDebugProxy();
+            }
+
             // Finally, use SPA fallback routing (serve default page for anything else,
             // excluding /_framework/*)
-            applicationBuilder.MapWhen(IsNotFrameworkDir, childAppBuilder =>
+            app.MapWhen(IsNotFrameworkDir, childAppBuilder =>
             {
                 childAppBuilder.UseSpa(spa =>
                 {
@@ -116,12 +122,18 @@ namespace Microsoft.AspNetCore.Builder
         private static bool IsNotFrameworkDir(HttpContext context)
             => !context.Request.Path.StartsWithSegments("/_framework");
 
-        private static IContentTypeProvider CreateContentTypeProvider()
+        private static IContentTypeProvider CreateContentTypeProvider(bool enableDebugging)
         {
             var result = new FileExtensionContentTypeProvider();
             result.Mappings.Add(".dll", MediaTypeNames.Application.Octet);
             result.Mappings.Add(".mem", MediaTypeNames.Application.Octet);
             result.Mappings.Add(".wasm", WasmMediaTypeNames.Application.Wasm);
+
+            if (enableDebugging)
+            {
+                result.Mappings.Add(".pdb", MediaTypeNames.Application.Octet);
+            }
+
             return result;
         }
     }

src/Microsoft.AspNetCore.Blazor.Server/BlazorConfig.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -15,6 +15,7 @@ namespace Microsoft.AspNetCore.Blazor.Server
         public string DistPath
             => Path.Combine(Path.GetDirectoryName(SourceOutputAssemblyPath), "dist");
         public bool EnableAutoRebuilding { get; }
+        public bool EnableDebugging { get; }
 
         public static BlazorConfig Read(string assemblyPath)
             => new BlazorConfig(assemblyPath);
@@ -44,6 +45,7 @@ namespace Microsoft.AspNetCore.Blazor.Server
             }
 
             EnableAutoRebuilding = configLines.Contains("autorebuild:true", StringComparer.Ordinal);
+            EnableDebugging = configLines.Contains("debug:true", StringComparer.Ordinal);
         }
     }
 }

src/Microsoft.AspNetCore.Blazor.Server/MonoDebugProxy/MonoDebugProxyAppBuilderExtensions.cs

@@ -0,0 +1,178 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
+using System.Net.Http;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+using Newtonsoft.Json;
+using WsProxy;
+
+namespace Microsoft.AspNetCore.Builder
+{
+    internal static class MonoDebugProxyAppBuilderExtensions
+    {
+        public static void UseMonoDebugProxy(this IApplicationBuilder app)
+        {
+            app.UseWebSockets();
+
+            app.Use((context, next) =>
+            {
+                var requestPath = context.Request.Path;
+                if (!requestPath.StartsWithSegments("/_framework/debug"))
+                {
+                    return next();
+                }
+
+                if (requestPath.Equals("/_framework/debug/ws-proxy", StringComparison.OrdinalIgnoreCase))
+                {
+                    return DebugWebSocketProxyRequest(context);
+                }
+
+                if (requestPath.Equals("/_framework/debug", StringComparison.OrdinalIgnoreCase))
+                {
+                    return DebugHome(context);
+                }
+
+                context.Response.StatusCode = (int)HttpStatusCode.NotFound;
+                return Task.CompletedTask;
+            });
+        }
+
+        private static async Task DebugWebSocketProxyRequest(HttpContext context)
+        {
+            if (!context.WebSockets.IsWebSocketRequest)
+            {
+                context.Response.StatusCode = 400;
+                return;
+            }
+
+            var browserUri = new Uri(context.Request.Query["browser"]);
+            await new MonoProxy().Run(context, browserUri);
+        }
+
+        private static async Task DebugHome(HttpContext context)
+        {
+            context.Response.ContentType = "text/html";
+
+            var request = context.Request;
+            var appRootUrl = $"{request.Scheme}://{request.Host}{request.PathBase}/";
+            var targetTabUrl = request.Query["url"];
+            if (string.IsNullOrEmpty(targetTabUrl))
+            {
+                context.Response.StatusCode = (int)HttpStatusCode.BadRequest;
+                await context.Response.WriteAsync("No value specified for 'url'");
+                return;
+            }
+
+            // TODO: Allow overriding port (but not hostname, as we're connecting to the
+            // local browser, not to the webserver serving the app)
+            var debuggerHost = "http://localhost:9222";
+            var debuggerTabsListUrl = $"{debuggerHost}/json";
+            IEnumerable<BrowserTab> availableTabs;
+
+            try
+            {
+                availableTabs = await GetOpenedBrowserTabs(debuggerHost);
+            }
+            catch (Exception ex)
+            {
+
+                await context.Response.WriteAsync($@"
+    <h1>Unable to find debuggable browser tab</h1>
+    <p>
+        Could not get a list of browser tabs from <code>{debuggerTabsListUrl}</code>.
+        Ensure Chrome is running with debugging enabled.
+    </p>
+    <h2>Resolution</h2>
+    {GetLaunchChromeInstructions(appRootUrl)}
+    <p>... then use that new tab for debugging.</p>
+    <h2>Underlying exception:</h2>
+    <pre>{ex}</pre>
+");
+                return;
+            }
+
+            var matchingTabs = availableTabs
+                .Where(t => t.Url.Equals(targetTabUrl, StringComparison.Ordinal))
+                .ToList();
+            if (matchingTabs.Count == 0)
+            {
+                await context.Response.WriteAsync($@"
+                    <h1>Unable to find debuggable browser tab</h1>
+                    <p>
+                        The response from <code>{debuggerTabsListUrl}</code> does not include
+                        any entry for <code>{targetTabUrl}</code>.
+                    </p>");
+                return;
+            }
+            else if (matchingTabs.Count > 1)
+            {
+                // TODO: Automatically disambiguate by adding a GUID to the page title
+                // when you press the debugger hotkey, include it in the querystring passed
+                // here, then remove it once the debugger connects.
+                await context.Response.WriteAsync($@"
+                    <h1>Multiple matching tabs are open</h1>
+                    <p>
+                        There is more than one browser tab at <code>{targetTabUrl}</code>.
+                        Close the ones you do not wish to debug, then refresh this page.
+                    </p>");
+                return;
+            }
+
+            // Now we know uniquely which tab to debug, construct the URL to the debug
+            // page and redirect there
+            var tabToDebug = matchingTabs.Single();
+            var underlyingV8Endpoint = tabToDebug.WebSocketDebuggerUrl;
+            var proxyEndpoint = $"{request.Host}{request.PathBase}/_framework/debug/ws-proxy?browser={WebUtility.UrlEncode(underlyingV8Endpoint)}";
+            var devToolsUrlAbsolute = new Uri(debuggerHost + tabToDebug.DevtoolsFrontendUrl);
+            var devToolsUrlWithProxy = $"{devToolsUrlAbsolute.Scheme}://{devToolsUrlAbsolute.Authority}{devToolsUrlAbsolute.AbsolutePath}?ws={proxyEndpoint}";
+            context.Response.Redirect(devToolsUrlWithProxy);
+        }
+
+        private static string GetLaunchChromeInstructions(string appRootUrl)
+        {
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                return $@"<p>Close this browser, then press Win+R and enter the following:</p>
+                          <p><strong><code>""%programfiles(x86)%\Google\Chrome\Application\chrome.exe"" --remote-debugging-port=9222 {appRootUrl}</code></strong></p>";
+            }
+            else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+            {
+                return $@"<p>Close this browser, then in a terminal window execute the following:</p>
+                          <p><strong><code>google-chrome --remote-debugging-port=9222 {appRootUrl}</code></strong></p>";
+            }
+            else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+            {
+                return $@"<p>Close this browser, then in a terminal window execute the following:</p>
+                          <p><strong><code>open /Applications/Google\ Chrome.app --remote-debugging-port=9222 {appRootUrl}</code></strong></p>";
+            }
+            else
+            {
+                throw new InvalidOperationException("Unknown OS platform");
+            }
+        }
+
+        private static async Task<IEnumerable<BrowserTab>> GetOpenedBrowserTabs(string debuggerHost)
+        {
+            using (var httpClient = new HttpClient { Timeout = TimeSpan.FromSeconds(5) })
+            {
+                var jsonResponse = await httpClient.GetStringAsync($"{debuggerHost}/json");
+                return JsonConvert.DeserializeObject<BrowserTab[]>(jsonResponse);
+            }
+        }
+
+        class BrowserTab
+        {
+            public string Type { get; set; }
+            public string Url { get; set; }
+            public string Title { get; set; }
+            public string DevtoolsFrontendUrl { get; set; }
+            public string WebSocketDebuggerUrl { get; set; }
+        }
+    }
+}

src/Microsoft.AspNetCore.Blazor.Server/MonoDebugProxy/ws-proxy/Startup.cs

@@ -44,11 +44,12 @@ namespace WsProxy
 			}
 		}
 		// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
+        /*
 		public void Configure (IApplicationBuilder app, IHostingEnvironment env)
 		{
 			//loggerFactory.AddConsole();
 			//loggerFactory.AddDebug();
-			//app.UseDeveloperExceptionPage ();
+			app.UseDeveloperExceptionPage ();
 
 			app.UseWebSockets (); app.UseRouter (router => {
 				router.MapGet ("devtools/page/{pageId}", async context => {
@@ -66,5 +67,6 @@ namespace WsProxy
 				});
 			});
 		}
+        */
 	}
 }

src/Microsoft.AspNetCore.Blazor.Server/MonoDebugProxy/ws-proxy/WsProxy.cs

@@ -263,9 +263,9 @@ namespace WsProxy {
 			Send (this.ide, o, token);
 		}
 
-		public async Task Run (HttpContext context)
+		public async Task Run (HttpContext context, Uri browserUri)
 		{
-			var browserUri = GetBrowserUri (context.Request.Path.ToString ());
+			//var browserUri = GetBrowserUri (context.Request.Path.ToString ());
 			Debug ("wsproxy start");
 			using (this.ide = await context.WebSockets.AcceptWebSocketAsync ()) {
 				Debug ("ide connected");

test/Microsoft.AspNetCore.Blazor.Build.Test/RuntimeDependenciesResolverTest.cs

@@ -58,15 +58,20 @@ namespace Microsoft.AspNetCore.Blazor.Build.Test
                  uncalled implementation code from mscorlib.dll anyway.
                  */
                 "Microsoft.AspNetCore.Blazor.Browser.dll",
+                "Microsoft.AspNetCore.Blazor.Browser.pdb",
                 "Microsoft.AspNetCore.Blazor.dll",
+                "Microsoft.AspNetCore.Blazor.pdb",
                 "Microsoft.Extensions.DependencyInjection.Abstractions.dll",
                 "Microsoft.Extensions.DependencyInjection.dll",
                 "Microsoft.JSInterop.dll",
+                "Microsoft.JSInterop.pdb",
                 "Mono.Security.dll",
                 "Mono.WebAssembly.Interop.dll",
+                "Mono.WebAssembly.Interop.pdb",
                 "mscorlib.dll",
                 "netstandard.dll",
                 "StandaloneApp.dll",
+                "StandaloneApp.pdb",
                 "System.dll",
                 "System.Collections.Concurrent.dll",
                 "System.Collections.dll",