In E2E tests, pass application assembly path to Blazor dev server

Author: SteveSandersonMS

src/Components/Blazor/Build/src/ReferenceFromSource.props

@@ -28,7 +28,7 @@
   <PropertyGroup>
     <RunCommand>dotnet</RunCommand>
     <_BlazorCliLocation>$(MSBuildThisFileDirectory)../../DevServer/src/bin/$(Configuration)/netcoreapp3.0/blazor-devserver.dll</_BlazorCliLocation>
-    <RunArguments>exec &quot;$(_BlazorCliLocation)&quot; serve &quot;$(MSBuildProjectDirectory)/$(OutputPath)$(TargetFileName)&quot; $(AdditionalRunArguments)</RunArguments>
+    <RunArguments>exec &quot;$(_BlazorCliLocation)&quot; serve --applicationpath &quot;$(MSBuildProjectDirectory)/$(OutputPath)$(TargetFileName)&quot; $(AdditionalRunArguments)</RunArguments>
   </PropertyGroup>
 
   <ItemGroup>

src/Components/Blazor/DevServer/src/Commands/ServeCommand.cs

@@ -23,28 +23,11 @@ public ServeCommand(CommandLineApplication parent)
 
             HelpOption("-?|-h|--help");
 
-            ApplicationPath = new CommandArgument()
-            {
-                Description = "Path to the client application dll",
-                MultipleValues = false,
-                Name = "<PATH>",
-                ShowInHelpText = true
-            };
-            Arguments.Add(ApplicationPath);
-
             OnExecute(Execute);
         }
 
-        public CommandArgument ApplicationPath { get; private set; }
-
         private int Execute()
         {
-            if (string.IsNullOrWhiteSpace(ApplicationPath.Value))
-            {
-                throw new InvalidOperationException($"Invalid value for parameter '{nameof(ApplicationPath)}'. Value supplied: '{ApplicationPath.Value}'");
-            }
-
-            Server.Startup.ApplicationAssembly = ApplicationPath.Value;
             Server.Program.BuildWebHost(RemainingArguments.ToArray()).Run();
             return 0;
         }

src/Components/Blazor/DevServer/src/Server/Startup.cs

@@ -17,7 +17,12 @@ namespace Microsoft.AspNetCore.Blazor.DevServer.Server
 {
     internal class Startup
     {
-        public static string ApplicationAssembly { get; set; }
+        public Startup(IConfiguration configuration)
+        {
+            Configuration = configuration;
+        }
+
+        public IConfiguration Configuration { get; }
 
         public void ConfigureServices(IServiceCollection services)
         {
@@ -35,7 +40,7 @@ public void ConfigureServices(IServiceCollection services)
 
         public void Configure(IApplicationBuilder app, IWebHostEnvironment environment, IConfiguration configuration)
         {
-            var applicationAssemblyFullPath = ResolveApplicationAssemblyFullPath(environment);
+            var applicationAssemblyFullPath = ResolveApplicationAssemblyFullPath();
 
             app.UseDeveloperExceptionPage();
             app.UseResponseCompression();
@@ -54,15 +59,22 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment environment,
             });
         }
 
-        private static string ResolveApplicationAssemblyFullPath(IWebHostEnvironment environment)
+        private string ResolveApplicationAssemblyFullPath()
         {
-            var applicationAssemblyFullPath = Path.Combine(environment.ContentRootPath, ApplicationAssembly);
-            if (!File.Exists(applicationAssemblyFullPath))
+            const string applicationPathKey = "applicationpath";
+            var configuredApplicationPath = Configuration.GetValue<string>(applicationPathKey);
+            if (string.IsNullOrEmpty(configuredApplicationPath))
+            {
+                throw new InvalidOperationException($"No value was supplied for the required option '{applicationPathKey}'.");
+            }
+
+            var resolvedApplicationPath = Path.GetFullPath(configuredApplicationPath);
+            if (!File.Exists(resolvedApplicationPath))
             {
-                throw new InvalidOperationException($"Application assembly not found at {applicationAssemblyFullPath}.");
+                throw new InvalidOperationException($"Application assembly not found at {resolvedApplicationPath}.");
             }
 
-            return applicationAssemblyFullPath;
+            return resolvedApplicationPath;
         }
 
         private static void EnableConfiguredPathbase(IApplicationBuilder app, IConfiguration configuration)

src/Components/Blazor/DevServer/src/build/Microsoft.AspNetCore.Blazor.DevServer.props

@@ -2,6 +2,6 @@
   <PropertyGroup>
     <_BlazorDevServerDll>$(MSBuildThisFileDirectory)../tools/blazor-devserver.dll</_BlazorDevServerDll>
     <RunCommand>dotnet</RunCommand>
-    <RunArguments>&quot;$(_BlazorDevServerDll)&quot; serve &quot;$(MSBuildProjectDirectory)/$(OutputPath)$(TargetFileName)&quot;</RunArguments>
+    <RunArguments>&quot;$(_BlazorDevServerDll)&quot; serve --applicationpath &quot;$(MSBuildProjectDirectory)/$(OutputPath)$(TargetFileName)&quot;</RunArguments>
   </PropertyGroup>
 </Project>

src/Components/test/E2ETest/Infrastructure/ServerFixtures/DevHostServerFixture.cs

@@ -22,7 +22,8 @@ protected override IWebHost CreateWebHost()
             {
                 "--urls", "http://127.0.0.1:0",
                 "--contentroot", ContentRoot,
-                "--pathbase", PathBase
+                "--pathbase", PathBase,
+                "--applicationpath", typeof(TProgram).Assembly.Location,
             };
 
             if (!string.IsNullOrEmpty(Environment))