Handle publicPath=/ in HMR. Fixes #1191.

Author: SteveSandersonMS

src/Microsoft.AspNetCore.SpaServices/Webpack/ConditionalProxyMiddleware.cs

@@ -22,6 +22,7 @@ internal class ConditionalProxyMiddleware
         private readonly RequestDelegate _next;
         private readonly ConditionalProxyMiddlewareOptions _options;
         private readonly string _pathPrefix;
+        private readonly bool _pathPrefixIsRoot;
 
         public ConditionalProxyMiddleware(
             RequestDelegate next,
@@ -35,14 +36,15 @@ public ConditionalProxyMiddleware(
 
             _next = next;
             _pathPrefix = pathPrefix;
+            _pathPrefixIsRoot = string.Equals(_pathPrefix, "/", StringComparison.Ordinal);
             _options = options;
             _httpClient = new HttpClient(new HttpClientHandler());
             _httpClient.Timeout = _options.RequestTimeout;
         }
 
         public async Task Invoke(HttpContext context)
         {
-            if (context.Request.Path.StartsWithSegments(_pathPrefix))
+            if (context.Request.Path.StartsWithSegments(_pathPrefix) || _pathPrefixIsRoot)
             {
                 var didProxyRequest = await PerformProxyRequest(context);
                 if (didProxyRequest)

src/Microsoft.AspNetCore.SpaServices/Webpack/WebpackDevMiddleware.cs

@@ -17,7 +17,10 @@ public static class WebpackDevMiddleware
 
         private static readonly JsonSerializerSettings jsonSerializerSettings = new JsonSerializerSettings
         {
-            ContractResolver = new CamelCasePropertyNamesContractResolver(),
+            // Note that the aspnet-webpack JS code specifically expects options to be serialized with
+            // PascalCase property names, so it's important to be explicit about this contract resolver
+            ContractResolver = new DefaultContractResolver(),
+
             TypeNameHandling = TypeNameHandling.None
         };