Fix ItemWithPath throwing on null/empty/whitespace path instead of generating malformed URLs

src/Microsoft.Graph/Extensions/DriveItemRequestBuilderExtensions.cs

@@ -44,14 +44,7 @@
     /// </summary>
     public static CustomDriveItemItemRequestBuilder ItemWithPath(this Microsoft.Graph.Drives.Item.Root.RootRequestBuilder rootRequestBuilder, string path)
     {
-        if (!string.IsNullOrEmpty(path))
-        {
-            if (!path.StartsWith("/"))
-            {
-                path = string.Format("/{0}", path);
-            }
-        }
-
+        path = NormalizePathOrThrow(path);
         var requestInformation = rootRequestBuilder.ToGetRequestInformation();
         // Encode the path in accordance with the one drive spec
         // https://docs.microsoft.com/en-us/onedrive/developer/rest-api/concepts/addressing-driveitems
@@ -67,14 +60,7 @@
     /// </summary>
     public static CustomDriveItemItemRequestBuilder ItemWithPath(this Microsoft.Graph.Drives.Item.Items.Item.DriveItemItemRequestBuilder rootRequestBuilder, string path)
     {
-        if (!string.IsNullOrEmpty(path))
-        {
-            if (!path.StartsWith("/"))
-            {
-                path = string.Format("/{0}", path);
-            }
-        }
-
+        path = NormalizePathOrThrow(path);
         var requestInformation = rootRequestBuilder.ToGetRequestInformation();
         // Encode the path in accordance with the one drive spec
         // https://docs.microsoft.com/en-us/onedrive/developer/rest-api/concepts/addressing-driveitems
@@ -84,29 +70,40 @@
         return new CustomDriveItemItemRequestBuilder(rootRequestBuilder.GetPathParameters(), rootRequestBuilder.GetRequestAdapter(),rootRequestBuilder.GetUrlTemplate().Replace("{driveItem%2Did}",$"{{driveItem%2Did}}:{parameter}:"));
     }
 
+    private static string NormalizePathOrThrow(string path)
+    {
+        if (path is null)
+            throw new ArgumentNullException(nameof(path));
+        if (string.IsNullOrWhiteSpace(path))
+            throw new ArgumentException("path cannot be empty or whitespace.", nameof(path));
+        if (!path.StartsWith("/", StringComparison.Ordinal))
+            path = string.Format("/{0}", path);
+        return path;
+    }
+
     private static IRequestAdapter GetRequestAdapter(this object obj) {
         var field = obj.GetType()
                         .BaseType!
                         .GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
                         .FirstOrDefault( field => field.FieldType == typeof(IRequestAdapter));
         return (IRequestAdapter)field?.GetValue(obj);
     }
     private static Dictionary<string, object> GetPathParameters(this object obj) {
         var field = obj.GetType()
             .BaseType!
             .GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
             .FirstOrDefault( field => field.FieldType == typeof(Dictionary<string, object>));
         return (Dictionary<string, object>)field?.GetValue(obj);
     }
     private static string GetUrlTemplate(this object obj) {
         var field = obj.GetType()
             .BaseType!
             .GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
             .FirstOrDefault( field => field.FieldType == typeof(string));
         return (string)field?.GetValue(obj);
     }
     internal static T UpdateUrlTemplate<T>(this T obj, string baseTemplate) where T : BaseRequestBuilder{
         var field = obj.GetType()
             .BaseType!
             .GetFields(BindingFlags.NonPublic | BindingFlags.Instance)
             .FirstOrDefault( field => field.FieldType == typeof(string));

tests/Microsoft.Graph.DotnetCore.Test/Requests/Extensions/DriveItemRequestBuilderExtensionsTests.cs

@@ -141,5 +141,41 @@ public void ItemByPath_BuildRequestWithNestedPathSlashAndMoreThanOneParameter()
             Assert.NotNull(itemRequestInformation);
             Assert.Equal(expectedRequestUri, itemRequestInformation.URI);
         }
+        [Fact]
+        public void ItemByPath_ThrowsArgumentNullException_WhenPathIsNull_Root()
+        {
+            var graphServiceClient = new GraphServiceClient(new MockAuthenticationProvider().Object);
+            var ex = Assert.Throws<ArgumentNullException>(() => graphServiceClient.Drives["driveId"].Root.ItemWithPath(null));
+            Assert.Equal("path", ex.ParamName);
+        }
+
+        [Theory]
+        [InlineData("")]
+        [InlineData("   ")]
+        public void ItemByPath_ThrowsArgumentException_WhenPathIsEmptyOrWhitespace_Root(string path)
+        {
+            var graphServiceClient = new GraphServiceClient(new MockAuthenticationProvider().Object);
+            var ex = Assert.Throws<ArgumentException>(() => graphServiceClient.Drives["driveId"].Root.ItemWithPath(path));
+            Assert.Equal("path", ex.ParamName);
+        }
+
+        [Fact]
+        public void ItemByPath_ThrowsArgumentNullException_WhenPathIsNull_DriveItem()
+        {
+            var graphServiceClient = new GraphServiceClient(new MockAuthenticationProvider().Object);
+            var ex = Assert.Throws<ArgumentNullException>(() => graphServiceClient.Drives["driveId"].Items["itemId"].ItemWithPath(null));
+            Assert.Equal("path", ex.ParamName);
+        }
+
+        [Theory]
+        [InlineData("")]
+        [InlineData("   ")]
+        public void ItemByPath_ThrowsArgumentException_WhenPathIsEmptyOrWhitespace_DriveItem(string path)
+        {
+            var graphServiceClient = new GraphServiceClient(new MockAuthenticationProvider().Object);
+            var ex = Assert.Throws<ArgumentException>(() => graphServiceClient.Drives["driveId"].Items["itemId"].ItemWithPath(path));
+            Assert.Equal("path", ex.ParamName);
+        }
+
     }
 }