Apply hosting environment via command line args (#34794)

* Apply hosting environment via command line args
- This makes sure that the entire applicaton can see changes to host configuration (env, content root etc).
- Added tests to verify those scenarios

Author: davidfowl

src/Mvc/Mvc.Testing/src/DeferredHostBuilder.cs

@@ -19,6 +19,8 @@ internal class DeferredHostBuilder : IHostBuilder
         private Action<IHostBuilder> _configure;
         private Func<string[], object>? _hostFactory;
 
+        private readonly ConfigurationManager _hostConfiguration = new();
+
         // This task represents a call to IHost.Start, we create it here preemptively in case the application
         // exits due to an exception or because it didn't wait for the shutdown signal
         private readonly TaskCompletionSource _hostStartTcs = new(TaskCreationOptions.RunContinuationsAsynchronously);
@@ -38,8 +40,18 @@ public DeferredHostBuilder()
 
         public IHost Build()
         {
+            // Hosting configuration is being provided by args so that
+            // we can impact WebApplicationBuilder based applications.
+            var args = new List<string>();
+
+            // Transform the host configuration into command line arguments
+            foreach (var (key, value) in _hostConfiguration.AsEnumerable())
+            {
+                args.Add($"--{key}={value}");
+            }
+
             // This will never be null if the case where Build is being called
-            var host = (IHost)_hostFactory!(Array.Empty<string>());
+            var host = (IHost)_hostFactory!(args.ToArray());
 
             // We can't return the host directly since we need to defer the call to StartAsync
             return new DeferredHost(host, _hostStartTcs);
@@ -59,7 +71,10 @@ public IHostBuilder ConfigureContainer<TContainerBuilder>(Action<HostBuilderCont
 
         public IHostBuilder ConfigureHostConfiguration(Action<IConfigurationBuilder> configureDelegate)
         {
-            _configure += b => b.ConfigureHostConfiguration(configureDelegate);
+            // Run this immediately so that we can capture the host configuration
+            // before we pass it to the application. We can do this for app configuration
+            // as well if it becomes necessary.
+            configureDelegate(_hostConfiguration);
             return this;
         }
 

src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

@@ -159,6 +159,7 @@ private void EnsureServer()
             if (builder is null)
             {
                 var deferredHostBuilder = new DeferredHostBuilder();
+                deferredHostBuilder.UseEnvironment(Environments.Development);
                 // This helper call does the hard work to determine if we can fallback to diagnostic source events to get the host instance
                 var factory = HostFactoryResolver.ResolveHostFactory(
                     typeof(TEntryPoint).Assembly,

src/Mvc/test/Mvc.FunctionalTests/SimpleWithWebApplicationBuilderTests.cs

@@ -1,30 +1,37 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Collections.Generic;
 using System.Net;
 using System.Net.Http;
 using System.Threading.Tasks;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.AspNetCore.Testing;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Hosting;
 using Xunit;
 
 namespace Microsoft.AspNetCore.Mvc.FunctionalTests
 {
     public class SimpleWithWebApplicationBuilderTests : IClassFixture<MvcTestFixture<SimpleWebSiteWithWebApplicationBuilder.FakeStartup>>
     {
+        private readonly MvcTestFixture<SimpleWebSiteWithWebApplicationBuilder.FakeStartup> _fixture;
+
         public SimpleWithWebApplicationBuilderTests(MvcTestFixture<SimpleWebSiteWithWebApplicationBuilder.FakeStartup> fixture)
         {
-            Client = fixture.CreateDefaultClient();
+            _fixture = fixture;
         }
 
-        public HttpClient Client { get; }
-
         [Fact]
         public async Task HelloWorld()
         {
             // Arrange
             var expected = "Hello World";
+            using var client = _fixture.CreateDefaultClient();
 
             // Act
-            var content = await Client.GetStringAsync("http://localhost/");
+            var content = await client.GetStringAsync("http://localhost/");
 
             // Assert
             Assert.Equal(expected, content);
@@ -35,9 +42,10 @@ public async Task JsonResult_Works()
         {
             // Arrange
             var expected = "{\"name\":\"John\",\"age\":42}";
+            using var client = _fixture.CreateDefaultClient();
 
             // Act
-            var response = await Client.GetAsync("/json");
+            var response = await client.GetAsync("/json");
 
             // Assert
             await response.AssertStatusCodeAsync(HttpStatusCode.OK);
@@ -50,9 +58,10 @@ public async Task OkObjectResult_Works()
         {
             // Arrange
             var expected = "{\"name\":\"John\",\"age\":42}";
+            using var client = _fixture.CreateDefaultClient();
 
             // Act
-            var response = await Client.GetAsync("/ok-object");
+            var response = await client.GetAsync("/ok-object");
 
             // Assert
             await response.AssertStatusCodeAsync(HttpStatusCode.OK);
@@ -65,9 +74,10 @@ public async Task AcceptedObjectResult_Works()
         {
             // Arrange
             var expected = "{\"name\":\"John\",\"age\":42}";
+            using var client = _fixture.CreateDefaultClient();
 
             // Act
-            var response = await Client.GetAsync("/accepted-object");
+            var response = await client.GetAsync("/accepted-object");
 
             // Assert
             await response.AssertStatusCodeAsync(HttpStatusCode.Accepted);
@@ -79,8 +89,11 @@ public async Task AcceptedObjectResult_Works()
         [Fact]
         public async Task ActionReturningMoreThanOneResult_NotFound()
         {
+            // Arrange
+            using var client = _fixture.CreateDefaultClient();
+
             // Act
-            var response = await Client.GetAsync("/many-results?id=-1");
+            var response = await client.GetAsync("/many-results?id=-1");
 
             // Assert
             await response.AssertStatusCodeAsync(HttpStatusCode.NotFound);
@@ -89,23 +102,75 @@ public async Task ActionReturningMoreThanOneResult_NotFound()
         [Fact]
         public async Task ActionReturningMoreThanOneResult_Found()
         {
+            // Arrange
+            using var client = _fixture.CreateDefaultClient();
+
             // Act
-            var response = await Client.GetAsync("/many-results?id=7");
+            var response = await client.GetAsync("/many-results?id=7");
 
             // Assert
             await response.AssertStatusCodeAsync(HttpStatusCode.MovedPermanently);
             Assert.Equal("/json", response.Headers.Location.ToString());
         }
 
         [Fact]
-        public async Task ActionReturningProblemDetails_ConfiguresContentType()
+        public async Task DefaultEnvironment_Is_Development()
+        {
+            // Arrange
+            var expected = "Development";
+            using var client = new WebApplicationFactory<SimpleWebSiteWithWebApplicationBuilder.FakeStartup>().CreateClient();
+
+            // Act
+            var content = await client.GetStringAsync("http://localhost/environment");
+
+            // Assert
+            Assert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task Configuration_Can_Be_Overridden()
         {
+            // Arrange
+            var fixture = _fixture.WithWebHostBuilder(builder =>
+            {
+                builder.ConfigureAppConfiguration(builder =>
+                {
+                    var config = new[]
+                    {
+                        KeyValuePair.Create("Greeting", "Bonjour tout le monde"),
+                    };
+
+                    builder.AddInMemoryCollection(config);
+                });
+            });
+
+            var expected = "Bonjour tout le monde";
+            using var client = fixture.CreateDefaultClient();
+
             // Act
-            var response = await Client.GetAsync("/problem");
+            var content = await client.GetStringAsync("http://localhost/greeting");
 
             // Assert
-            await response.AssertStatusCodeAsync(HttpStatusCode.InternalServerError);
-            Assert.Equal("application/problem+json", response.Content.Headers.ContentType.ToString());
+            Assert.Equal(expected, content);
+        }
+
+        [Fact]
+        public async Task Environment_Can_Be_Overridden()
+        {
+            // Arrange
+            var fixture = _fixture.WithWebHostBuilder(builder =>
+            {
+                builder.UseEnvironment(Environments.Staging);
+            });
+
+            var expected = "Staging";
+            using var client = fixture.CreateDefaultClient();
+
+            // Act
+            var content = await client.GetStringAsync("http://localhost/environment");
+
+            // Assert
+            Assert.Equal(expected, content);
         }
     }
 }

src/Mvc/test/WebSites/SimpleWebSiteWithWebApplicationBuilder/Program.cs

@@ -25,6 +25,10 @@
 
 app.MapGet("/problem", () => Results.Problem("Some problem"));
 
+app.MapGet("/environment", (IHostEnvironment environment) => environment.EnvironmentName);
+
+app.MapGet("/greeting", (IConfiguration config) => config["Greeting"]);
+
 app.Run();
 
 record Person(string Name, int Age);