Improve initialization and SignalR configuration

Fixes: #6887 and #6887 and #5624

Adds support for calling Blazor.start({...}) and passing in a
configuration object.

For now all you can configure is the SignalR HubConnectionBuilder. This
is a priority right now because we want to make configuring SignalR's
logging accessible.

src/Components/Browser.JS/src/Boot.Server.ts

@@ -2,7 +2,7 @@ import '@dotnet/jsinterop';
 import './GlobalExports';
 import * as signalR from '@aspnet/signalr';
 import { MessagePackHubProtocol } from '@aspnet/signalr-protocol-msgpack';
-import { fetchBootConfigAsync, loadEmbeddedResourcesAsync } from './BootCommon';
+import { fetchBootConfigAsync, loadEmbeddedResourcesAsync, shouldAutoStart } from './BootCommon';
 import { CircuitHandler } from './Platform/Circuits/CircuitHandler';
 import { AutoReconnectCircuitHandler } from './Platform/Circuits/AutoReconnectCircuitHandler';
 import RenderQueue from './Platform/Circuits/RenderQueue';
@@ -10,9 +10,21 @@ import { ConsoleLogger } from './Platform/Logging/Loggers';
 import { LogLevel, ILogger } from './Platform/Logging/ILogger';
 import { discoverPrerenderedCircuits, startCircuit } from './Platform/Circuits/CircuitManager';
 
-let renderingFailed = false;
 
-async function boot(): Promise<void> {
+type SignalRBuilder = (builder: signalR.HubConnectionBuilder) => void;
+interface BlazorOptions {
+  configureSignalR?: SignalRBuilder,
+};
+
+let renderingFailed = false;
+let started = false;
+
+async function boot(options?: BlazorOptions): Promise<void> {
+
+  if (started) {
+    throw new Error('Blazor has already started.');
+  }
+  started = true;
 
   // For development.
   // Simply put a break point here and modify the log level during
@@ -30,7 +42,9 @@ async function boot(): Promise<void> {
     return loadEmbeddedResourcesAsync(bootConfig);
   });
 
-  const initialConnection = await initializeConnection(circuitHandlers, logger);
+  // pass options.configureSignalR to configure the signalR.HubConnectionBuilder
+  const configureSignalR = (options && options.configureSignalR) || null;
+  const initialConnection = await initializeConnection(configureSignalR, circuitHandlers, logger);
 
   const circuits = discoverPrerenderedCircuits(document);
   for (let i = 0; i < circuits.length; i++) {
@@ -55,7 +69,7 @@ async function boot(): Promise<void> {
       // We can't reconnect after a failure, so exit early.
       return false;
     }
-    const reconnection = await initializeConnection(circuitHandlers, logger);
+    const reconnection = await initializeConnection(configureSignalR, circuitHandlers, logger);
     const results = await Promise.all(circuits.map(circuit => circuit.reconnect(reconnection)));
 
     if (reconnectionFailed(results)) {
@@ -81,14 +95,20 @@ async function boot(): Promise<void> {
   }
 }
 
-async function initializeConnection(circuitHandlers: CircuitHandler[], logger: ILogger): Promise<signalR.HubConnection> {
+async function initializeConnection(configureSignalR: SignalRBuilder | null, circuitHandlers: CircuitHandler[], logger: ILogger): Promise<signalR.HubConnection> {
+
   const hubProtocol = new MessagePackHubProtocol();
   (hubProtocol as any).name = 'blazorpack';
-  const connection = new signalR.HubConnectionBuilder()
+
+  const connectionBuilder = new signalR.HubConnectionBuilder()
     .withUrl('_blazor')
-    .withHubProtocol(hubProtocol)
-    .configureLogging(signalR.LogLevel.Information)
-    .build();
+    .withHubProtocol(hubProtocol);
+
+  if (configureSignalR) {
+    configureSignalR(connectionBuilder);
+  }
+
+  const connection = connectionBuilder.build();
 
   connection.on('JS.BeginInvokeJS', DotNet.jsCallDispatcher.beginInvokeJSFromDotNet);
   connection.on('JS.RenderBatch', (browserRendererId: number, batchId: number, batchData: Uint8Array) => {
@@ -131,4 +151,7 @@ function unhandledError(connection: signalR.HubConnection, err: Error, logger: I
   }
 }
 
-boot();
+window['Blazor'].start = boot;
+if (shouldAutoStart()) {
+  boot();
+}

src/Components/Browser.JS/src/Boot.WebAssembly.ts

@@ -6,9 +6,17 @@ import { getAssemblyNameFromUrl } from './Platform/Url';
 import { renderBatch } from './Rendering/Renderer';
 import { SharedMemoryRenderBatch } from './Rendering/RenderBatch/SharedMemoryRenderBatch';
 import { Pointer } from './Platform/Platform';
-import { fetchBootConfigAsync, loadEmbeddedResourcesAsync } from './BootCommon';
+import { fetchBootConfigAsync, loadEmbeddedResourcesAsync, shouldAutoStart } from './BootCommon';
+
+let started = false;
+
+async function boot(options?: any) {
+
+  if (started) {
+    throw new Error('Blazor has already started.');
+  }
+  started = true;
 
-async function boot() {
   // Configure environment for execution under Mono WebAssembly with shared-memory rendering
   const platform = Environment.setPlatform(monoPlatform);
   window['Blazor'].platform = platform;
@@ -43,4 +51,7 @@ async function boot() {
   platform.callEntryPoint(mainAssemblyName, bootConfig.entryPoint, []);
 }
 
-boot();
+window['Blazor'].start = boot;
+if (shouldAutoStart()) {
+  boot();
+}

src/Components/Browser.JS/src/BootCommon.ts

@@ -37,3 +37,10 @@ interface BootJsonData {
   jsReferences: string[];
   linkerEnabled: boolean;
 }
+
+// Tells you if the script was added without <script src="..." autostart="false"></script>
+export function shouldAutoStart() {
+  return document &&
+    document.currentScript &&
+    document.currentScript.getAttribute('autostart') !== 'false';
+}

src/Components/Browser.JS/src/GlobalExports.ts

@@ -1,8 +1,6 @@
-import { platform } from './Environment';
 import { navigateTo, internalFunctions as uriHelperInternalFunctions } from './Services/UriHelper';
 import { internalFunctions as httpInternalFunctions } from './Services/Http';
 import { attachRootComponentToElement } from './Rendering/Renderer';
-import { Pointer } from './Platform/Platform';
 
 // Make the following APIs available in global scope for invocation from JS
 window['Blazor'] = {
@@ -13,4 +11,4 @@ window['Blazor'] = {
     http: httpInternalFunctions,
     uriHelper: uriHelperInternalFunctions
   }
-};
+};

src/Components/Components.sln

@@ -210,6 +210,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 		..\..\.editorconfig = ..\..\.editorconfig
 	EndProjectSection
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.AspNetCore.Mvc.Components.Prerendering", "..\Mvc\Mvc.Components.Prerendering\src\Microsoft.AspNetCore.Mvc.Components.Prerendering.csproj", "{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -1324,6 +1326,18 @@ Global
 		{9088E4E4-B855-457F-AE9E-D86709A5E1F4}.Release|x64.Build.0 = Debug|Any CPU
 		{9088E4E4-B855-457F-AE9E-D86709A5E1F4}.Release|x86.ActiveCfg = Debug|Any CPU
 		{9088E4E4-B855-457F-AE9E-D86709A5E1F4}.Release|x86.Build.0 = Debug|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Debug|x64.Build.0 = Debug|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Debug|x86.Build.0 = Debug|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Release|x64.ActiveCfg = Release|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Release|x64.Build.0 = Release|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Release|x86.ActiveCfg = Release|Any CPU
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -1423,6 +1437,7 @@ Global
 		{04262990-929C-42BF-85A9-21C25FA95617} = {2FC10057-7A0A-4E34-8302-879925BC0102}
 		{DC47C40A-FC38-44E4-94A4-ADE794E76309} = {2FC10057-7A0A-4E34-8302-879925BC0102}
 		{9088E4E4-B855-457F-AE9E-D86709A5E1F4} = {7260DED9-22A9-4E9D-92F4-5E8A4404DEAF}
+		{3A4132B6-60DA-43A0-8E7B-4BF346F3247C} = {2FC10057-7A0A-4E34-8302-879925BC0102}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {CC3C47E1-AD1A-4619-9CD3-E08A0148E5CE}

src/Components/test/testassets/BasicTestApp/wwwroot/index.html

@@ -3,7 +3,7 @@
 <head>
     <meta charset="utf-8" />
     <title>Basic test app</title>
-    <base href="/subdir/" />    
+    <base href="/subdir/" />
     <link href="style.css" rel="stylesheet" />
 </head>
 <body>

src/Components/test/testassets/ComponentsApp.Server/Pages/Index.cshtml

@@ -15,7 +15,13 @@
 
     <app>@(await Html.RenderComponentAsync<App>(new { Name="Guest" }))</app>
 
-    <script src="_framework/components.server.js"></script>
-
+    <script src="_framework/components.server.js" autostart="false"></script>
+    <script>
+        Blazor.start({
+            configureSignalR: function (builder) {
+                builder.configureLogging(2); // LogLevel.Information
+            }
+        });
+    </script>
 </body>
 </html>

src/Components/test/testassets/TestServer/Pages/PrerenderedHost.cshtml

@@ -15,15 +15,11 @@
         interactive states, we only load the .js file when told to.
     *@
     <hr />
-    <button id="load-boot-script" onclick="loadBootScript(event)">Load boot script</button>
-    <script>
-    function loadBootScript(event) {
-        event.srcElement.disabled = true;
-        var scriptElem = document.createElement('script');
-        scriptElem.src = '_framework/components.server.js';
-        document.body.appendChild(scriptElem);
-    }
 
+    <button id="load-boot-script" onclick="Blazor.start()">Load boot script</button>
+
+    <script src="_framework/components.server.js" autostart="false"></script>
+    <script>
     // Used by InteropOnInitializationComponent
     function setElementValue(element, newValue) {
       element.value = newValue;