Support trailing slashes in paths

src/Microsoft.OpenApi/Services/OpenApiUrlTreeNode.cs

@@ -150,6 +150,13 @@ public OpenApiUrlTreeNode Attach(string path,
             }
 
             var segments = path.Split('/');
+            if (path.EndsWith("/", StringComparison.OrdinalIgnoreCase))
+            {
+                // Remove the last element, which is empty, and append the trailing slash to the new last element
+                // This is to support URLs with trailing slashes
+                Array.Resize(ref segments, segments.Length - 1);
+                segments[segments.Length - 1] += "/";
+            }
 
             return Attach(segments: segments,
                           pathItem: pathItem,

test/Microsoft.OpenApi.Tests/Services/OpenApiUrlTreeNodeTests.cs

@@ -466,5 +466,38 @@ public async Task VerifyDiagramFromSampleOpenAPI()
 
             await Verifier.Verify(diagram);
         }
+
+        public static TheoryData<string, string[], string, string> SupportsTrailingSlashesInPathData => new TheoryData<string, string[], string, string>
+        {
+            // Path, children up to second to leaf, last expected leaf node name, expected leaf node path
+            { "/cars/{car-id}/build/", ["cars", "{car-id}"], "build/", @"\cars\{car-id}\build/" },
+            { "/cars/", [], "cars/", @"\cars/" },
+        };
+
+        [Theory]
+        [MemberData(nameof(SupportsTrailingSlashesInPathData))]
+        public void SupportsTrailingSlashesInPath(string path, string[] childrenBeforeLastNode, string expectedLeafNodeName, string expectedLeafNodePath)
+        {
+            var openApiDocument = new OpenApiDocument
+            {
+                Paths = new()
+                {
+                    [path] = new()
+                }
+            };
+
+            var label = "trailing-slash";
+            var rootNode = OpenApiUrlTreeNode.Create(openApiDocument, label);
+
+            var secondToLeafNode = rootNode;
+            foreach (var childName in childrenBeforeLastNode)
+            {
+                secondToLeafNode = secondToLeafNode.Children[childName];
+            }
+
+            Assert.True(secondToLeafNode.Children.TryGetValue(expectedLeafNodeName, out var leafNode));
+            Assert.Equal(expectedLeafNodePath, leafNode.Path);
+            Assert.Empty(leafNode.Children);
+        }
     }
 }