Fix "e.map is not a function" JS exception in the UI

src/HealthChecks.UI/Extensions/ApplicationBuilderExtensions.cs

@@ -2,6 +2,7 @@
 using HealthChecks.UI.Configuration;
 using HealthChecks.UI.Core;
 using HealthChecks.UI.Middleware;
+using Microsoft.AspNetCore.Routing;
 
 namespace Microsoft.AspNetCore.Builder;
 
@@ -22,7 +23,11 @@ public static IApplicationBuilder UseHealthChecksUI(this IApplicationBuilder app
 
     private static IApplicationBuilder ConfigurePipeline(IApplicationBuilder app, Options options)
     {
-        EnsureValidApiOptions(options);
+        EnsureValidApiOptions(options,
+         (app.ApplicationServices.GetService(typeof(IEnumerable<EndpointDataSource>)) as IEnumerable<EndpointDataSource>)
+             ?.SelectMany(dataSource => dataSource.Endpoints)
+             ?.OfType<RouteEndpoint>());
+
 
         var embeddedResourcesAssembly = typeof(UIResource).Assembly;
 
@@ -44,7 +49,7 @@ private static IApplicationBuilder ConfigurePipeline(IApplicationBuilder app, Op
         return app;
     }
 
-    private static void EnsureValidApiOptions(Options options)
+    private static void EnsureValidApiOptions(Options options, IEnumerable<RouteEndpoint>? routeEndpoints)
     {
         Action<string, string> ensureValidPath = (string path, string argument) =>
         {
@@ -57,5 +62,15 @@ private static void EnsureValidApiOptions(Options options)
         ensureValidPath(options.ApiPath, nameof(Options.ApiPath));
         ensureValidPath(options.UIPath, nameof(Options.UIPath));
         ensureValidPath(options.WebhookPath, nameof(Options.WebhookPath));
+
+        Func<string, string> normalizeUriPath = (string path) =>
+            path.TrimEnd('/').ToLower();
+
+        if (routeEndpoints
+            ?.Select(endPoint => normalizeUriPath(endPoint.RoutePattern.RawText ?? string.Empty))
+            ?.Count(path => path == normalizeUriPath(options.ApiPath)) > 0)
+        {
+            throw new ArgumentException("ApiPath should not match any route registered via MapHealthChecks!");
+        }
     }
 }

test/HealthChecks.UI.Tests/Functional/Configuration/UIConfigurationTests.cs

@@ -334,4 +334,32 @@ public async Task support_configuring_page_title()
 
         html.ShouldContain($"<title>{pageTitle}</title>");
     }
+
+    [Theory]
+    [InlineData("/healthz")]
+    [InlineData("/healthz/")]
+    [InlineData("/Healthz")]
+    public void throws_when_api_path_mounted_on_existing_health_check(string endPoint)
+    {
+        var builder = new WebHostBuilder()
+            .ConfigureServices(services =>
+            {
+                services
+                    .AddRouting()
+                    .AddHealthChecksUI()
+                    .AddInMemoryStorage()
+                    .Services
+                    .AddHealthChecks();
+            })
+            .Configure(app =>
+            {
+                app
+                    .UseRouting()
+                    .UseEndpoints(setup => setup.MapHealthChecks(endPoint, new HealthCheckOptions()))
+                    .UseHealthChecksUI(setup => setup.ApiPath = "/healthz");
+            });
+
+        var exception = Assert.Throws<ArgumentException>(() => new TestServer(builder));
+        Assert.Equal("ApiPath should not match any route registered via MapHealthChecks!", exception.Message);
+    }
 }