Improve IIS error when wrong application path (dotnet#46249)

Author: BrennanConroy

src/Servers/IIS/AspNetCoreModuleV2/AspNetCore/HandlerResolver.cpp

@@ -321,10 +321,21 @@ try
                 errorContext.generalErrorType = "Failed to load ASP.NET Core runtime";
                 errorContext.errorReason = "The specified version of Microsoft.NetCore.App or Microsoft.AspNetCore.App was not found.";
 
-                EventLog::Error(
-                    ASPNETCORE_EVENT_GENERAL_ERROR,
-                    ASPNETCORE_EVENT_HOSTFXR_FAILURE_MSG
-                );
+                if (intHostFxrExitCode == AppArgNotRunnable)
+                {
+                    errorContext.detailedErrorContent = "Provided application path does not exist, or isn't a .dll or .exe.";
+                    EventLog::Error(
+                        ASPNETCORE_EVENT_GENERAL_ERROR,
+                        ASPNETCORE_EVENT_HOSTFXR_BAD_APPLICATION_FAILURE_MSG
+                    );
+                }
+                else
+                {
+                    EventLog::Error(
+                        ASPNETCORE_EVENT_GENERAL_ERROR,
+                        ASPNETCORE_EVENT_HOSTFXR_FAILURE_MSG
+                    );
+                }
 
                 return E_UNEXPECTED;
             }

src/Servers/IIS/AspNetCoreModuleV2/CommonLib/HostFxr.h

@@ -30,6 +30,8 @@ typedef int(*hostfxr_get_runtime_property_value_fn)(void* host_context_handle, P
 typedef int(*hostfxr_run_app_fn)(void* host_context_handle);
 typedef int(*hostfxr_close_fn)(void* hostfxr_context_handle);
 
+const int AppArgNotRunnable = 0x80008094;
+
 class HostFxrErrorRedirector: NonCopyable
 {
 public:

src/Servers/IIS/AspNetCoreModuleV2/CommonLib/resources.h

@@ -41,6 +41,7 @@
 #define ASPNETCORE_EVENT_HOSTFXR_DLL_INVALID_VERSION_MSG     L"Hostfxr version used does not support 'hostfxr_get_native_search_directories', update the version of hostfxr to a higher version. Path to hostfxr: '%s'."
 #define ASPNETCORE_EVENT_HOSTFXR_DLL_UNABLE_TO_LOAD_MSG      L"Unable to load '%s'. This might be caused by a bitness mismatch between IIS application pool and published application."
 #define ASPNETCORE_EVENT_HOSTFXR_FAILURE_MSG                 L"Unable to locate application dependencies. Ensure that the versions of Microsoft.NetCore.App and Microsoft.AspNetCore.App targeted by the application are installed."
+#define ASPNETCORE_EVENT_HOSTFXR_BAD_APPLICATION_FAILURE_MSG L"Provided application path does not exist, or isn't a .dll or .exe."
 #define ASPNETCORE_EVENT_INPROCESS_THREAD_EXCEPTION_MSG      L"Application '%s' with physical root '%s' hit unexpected managed exception, exception code = '0x%x'. Please check the stderr logs for more information."
 #define ASPNETCORE_EVENT_INPROCESS_THREAD_EXCEPTION_STDOUT_MSG L"Application '%s' with physical root '%s' hit unexpected managed exception, exception code = '0x%x'. First 30KB characters of captured stdout and stderr logs:\r\n%s"
 #define ASPNETCORE_EVENT_INPROCESS_RH_ERROR_MSG              L"Could not find 'aspnetcorev2_inprocess.dll'. Exception message:\r\n%s"

src/Servers/IIS/IIS/test/Common.FunctionalTests/Infrastructure/EventLogHelpers.cs

@@ -262,6 +262,11 @@ public static string InProcessFailedToFindNativeDependencies(IISDeploymentResult
         }
     }
 
+    public static string InProcessFailedToFindApplication()
+    {
+        return "Provided application path does not exist, or isn't a .dll or .exe.";
+    }
+
     public static string InProcessFailedToFindRequestHandler(IISDeploymentResult deploymentResult)
     {
         if (DeployerSelector.HasNewShim)

src/Servers/IIS/IIS/test/Common.LongTests/StartupTests.cs

@@ -357,7 +357,7 @@ public async Task RemoveHostfxrFromApp_InProcessHostfxrLoadFailure()
     }
 
     [ConditionalFact]
-    public async Task TargedDifferenceSharedFramework_FailedToFindNativeDependencies()
+    public async Task TargetDifferenceSharedFramework_FailedToFindNativeDependencies()
     {
         var deploymentParameters = Fixture.GetBaseDeploymentParameters(Fixture.InProcessTestSite);
         var deploymentResult = await DeployAsync(deploymentParameters);
@@ -375,6 +375,25 @@ public async Task TargedDifferenceSharedFramework_FailedToFindNativeDependencies
         EventLogHelpers.VerifyEventLogEvent(deploymentResult, EventLogHelpers.InProcessFailedToFindNativeDependencies(deploymentResult), Logger);
     }
 
+    [ConditionalFact]
+    [RequiresNewShim]
+    public async Task WrongApplicationPath_FailedToRun()
+    {
+        var deploymentParameters = Fixture.GetBaseDeploymentParameters(Fixture.InProcessTestSite);
+        deploymentParameters.WebConfigBasedEnvironmentVariables["ASPNETCORE_DETAILEDERRORS"] = "TRUE";
+        var deploymentResult = await DeployAsync(deploymentParameters);
+
+        deploymentResult.ModifyWebConfig(element => element
+            .Descendants("system.webServer")
+            .Single()
+            .GetOrAdd("aspNetCore")
+            .SetAttributeValue("arguments", "not-exist.dll"));
+
+        await AssertSiteFailsToStartWithInProcessStaticContent(deploymentResult, "500.31", "Provided application path does not exist, or isn't a .dll or .exe.");
+
+        EventLogHelpers.VerifyEventLogEvent(deploymentResult, EventLogHelpers.InProcessFailedToFindApplication(), Logger);
+    }
+
     [ConditionalFact]
     public async Task SingleExecutable_FailedToFindNativeDependencies()
     {
@@ -1559,4 +1578,23 @@ private async Task AssertSiteFailsToStartWithInProcessStaticContent(IISDeploymen
         Assert.Contains(error, await response.Content.ReadAsStringAsync());
         StopServer();
     }
+
+    private async Task AssertSiteFailsToStartWithInProcessStaticContent(IISDeploymentResult deploymentResult, params string[] errors)
+    {
+        HttpResponseMessage response = null;
+
+        // Make sure strings aren't freed.
+        for (var i = 0; i < 2; i++)
+        {
+            response = await deploymentResult.HttpClient.GetAsync("/HelloWorld");
+        }
+
+        Assert.Equal(HttpStatusCode.InternalServerError, response.StatusCode);
+        var responseText = await response.Content.ReadAsStringAsync();
+        foreach (var error in errors)
+        {
+            Assert.Contains(error, responseText);
+        }
+        StopServer();
+    }
 }