fix: allow patch to singletons

MockData/ActionV4Tests.PatchMovieDetails.1.txt

@@ -0,0 +1 @@
+{"Content":"{\"@odata.type\":\"#WebApiOData.V4.Samples.Models.MovieDetails\",\"Synopsis\":\"Foo!\"}","ContentHeaders":[{"Key":"Content-Type","Value":["application\/json"]},{"Key":"Content-Length","Value":["48"]}],"Method":"PATCH","RequestHeaders":[{"Key":"Accept","Value":["application\/json","application\/xml","application\/text"]},{"Key":"Prefer","Value":["return=representation"]}],"RequestUri":"http:\/\/localhost\/actions\/Movies\/1/Details"}

MockData/ActionV4Tests.PatchMovieDetails.2.txt

@@ -0,0 +1 @@
+{"Content":"{\"@odata.context\":\"http://localhost/actions/$metadata#Movies(1)/Details\",\"value\":[{\"Synopsis\":\"Foo!\"}]}","ContentHeaders":[{"Key":"Content-Type","Value":["application\/json; odata.metadata=minimal"]},{"Key":"Content-Length","Value":["148"]}],"RequestUri":"http:\/\/localhost\/actions\/Movies\/1/Details","ResponseHeaders":[{"Key":"OData-Version","Value":["4.0"]}],"StatusCode":200}

src/Simple.OData.Client.Core/Adapter/RequestWriterBase.cs

@@ -99,7 +99,7 @@ public async Task<ODataRequest> CreateUpdateRequestAsync(
 
 		var hasPropertiesToUpdate = entryDetails.Properties.Count > 0;
 		var usePatch = _session.Settings.PreferredUpdateMethod == ODataUpdateMethod.Patch || !hasPropertiesToUpdate;
-		if (HasUpdatedKeyProperties(collection, entryKey, entryData))
+		if (entryKey != null && HasUpdatedKeyProperties(collection, entryKey, entryData))
 		{
 			usePatch = false;
 		}

src/Simple.OData.Client.Core/Fluent/RequestBuilder.cs

@@ -81,8 +81,6 @@ public async Task<ODataRequest> UpdateRequestAsync(
 		bool resultRequired,
 		CancellationToken cancellationToken)
 	{
-		AssertHasKey(_command);
-
 		await _session
 			.ResolveAdapterAsync(cancellationToken)
 			.ConfigureAwait(false);

src/WebApiOData.V4.Samples.Tests/ActionV4Tests.cs

@@ -151,4 +151,16 @@ public async Task CreateMovie_batch()
 
 		Assert.True(result.ID > 0);
 	}
+
+	[Fact]
+	public async Task PatchMovieDetails()
+	{
+		var settings = CreateDefaultSettings().WithHttpMock();
+		var client = new ODataClient(settings);
+		MovieDetails updated = await client.For<Movie>().Key(1).NavigateTo(m => m.Details!).Set(new
+		{
+			Synopsis = "Foo!"
+		}).UpdateEntryAsync().ConfigureAwait(false);
+		Assert.Equal("Foo!", updated.Synopsis);
+	}
 }

src/WebApiOData.V4.Samples.Tests/Resources/Metadata.xml

@@ -10,6 +10,10 @@
         <Property Name="Title" Type="Edm.String" />
         <Property Name="Year" Type="Edm.Int32" Nullable="false" />
         <Property Name="DueDate" Type="Edm.DateTimeOffset" />
+        <NavigationProperty Name="Details" Type="WebApiOData.V4.Samples.Models.MovieDetails" />
+      </EntityType>
+      <EntityType Name="MovieDetails">
+        <Property Name="Synopsis" Type="Edm.String" />
       </EntityType>
       <EntityType Name="Product">
         <Key>

src/WebApiOData.V4.Samples/Controllers/MoviesController.cs

@@ -17,6 +17,28 @@ public IHttpActionResult Get()
 		return Ok(_db.Movies);
 	}
 
+	public IHttpActionResult GetMovieDetails(int key) 
+	{
+		var movie = _db.Movies.FirstOrDefault(m => m.ID == key);
+		if (movie?.Details is not null)
+		{
+			return Ok(movie.Details);
+		}
+		return NotFound();
+	}
+
+	[HttpPatch]
+	public IHttpActionResult PatchToMovieDetails(int key, Delta<MovieDetails> delta) 
+	{
+		var movie = _db.Movies.FirstOrDefault(m => m.ID == key);
+		if (movie?.Details is not null)
+		{
+			delta?.Patch(movie.Details);
+			return Ok(movie.Details);
+		}
+		return NotFound();
+	}
+
 	[HttpPost]
 	public IHttpActionResult CheckOut(int key)
 	{

src/WebApiOData.V4.Samples/Models/Movie.cs

@@ -13,4 +13,11 @@ public class Movie
 	public DateTimeOffset? DueDate { get; set; }
 
 	public bool IsCheckedOut => DueDate.HasValue;
+
+	public MovieDetails? Details { get; set; }
 }
+
+public class MovieDetails
+{
+	public string Synopsis { get; set; } = string.Empty;
+}

src/WebApiOData.V4.Samples/Models/MoviesContext.cs

@@ -6,7 +6,7 @@ public class MoviesContext
 {
 	public List<Movie> Movies { get; set; } = new List<Movie>()
 			{
-				new Movie() { ID=1, Title = "Maximum Payback", Year = 1990 },
+				new Movie() { ID=1, Title = "Maximum Payback", Year = 1990, Details = new() { Synopsis = "..." } },
 				new Movie() { ID=2, Title = "Inferno of Retribution", Year = 2005 },
 				new Movie() { ID=3, Title = "Fatal Vengeance 2", Year = 2012 },
 				new Movie() { ID=4, Title = "Sudden Danger", Year = 2012 },

src/WebApiOData.V4.Samples/Startups/ActionStartup.cs

@@ -29,6 +29,8 @@ private static IEdmModel GetEdmModel(HttpConfiguration config)
 		var modelBuilder = new ODataConventionModelBuilder(config);
 		_ = modelBuilder.EntitySet<Movie>("Movies");
 
+		modelBuilder.EntityType<Movie>().HasOptional(m => m.Details!).Contained();
+
 		// Now add actions.
 
 		// CheckOut