Allow nulls in getReferenceAsync

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## Unreleased: 2.0.1
+
+### Fixed
+
+- Properly annotate the `getReferenceAsync` delegate to allow nulls, which fixes the mismatch in analysis.
+
 ## 2.0.0 - 2022-11-05
 
 This version introduces breaking changes. Make sure to read on them in the Changed section below.

README.md

@@ -44,7 +44,7 @@ services.AddPagination(options =>
 
 Check the [`PaginationOptions`](https://github.com/mrahhal/MR.AspNetCore.Pagination/blob/main/src/MR.AspNetCore.Pagination/PaginationOptions.cs) class to see what you can configure.
 
-And then just inject `IPaginationService` in your controller/page and use it. The [returned result](https://github.com/mrahhal/MR.AspNetCore.Pagination/blob/main/src/MR.AspNetCore.Pagination/PaginationResult.cs) is either a `KeysetPaginationResult<>` or an `OffsetPaginationResult<>`, each containing all the info you need for this pagination result. 
+And then just inject `IPaginationService` in your controller/page and use it. The [returned result](https://github.com/mrahhal/MR.AspNetCore.Pagination/blob/main/src/MR.AspNetCore.Pagination/PaginationResult.cs) is either a `KeysetPaginationResult<>` or an `OffsetPaginationResult<>`, each containing all the info you need for this pagination result.
 
 Do a keyset pagination:
 
@@ -110,6 +110,27 @@ var result = _paginationService.OffsetPaginate(orders);
 
 There's a helper `PaginationActionDetector` class that can be used with reflection, for example in ASP.NET Core conventions, which can tell you whether the action method returns a pagination result or not. This is what the MR.AspNetCore.Pagination.Swashbuckle package uses to configure swagger for those apis.
 
+## Handling null references (reference has been deleted from the db)
+
+The `getReferenceAsync` delegate parameter on `KeysetPaginateAsync` that you'll provide allows returning nulls. The behavior when that happens is to always return the first page (enforcing Forward direction).
+
+If you want to have a special way to handle this, you'll simply have to do that logic in the `getReferenceAsync` delegate you'll provide. Here's an example:
+```cs
+var result = await _paginationService.KeysetPaginateAsync(
+    query,
+    b => b.Descending(x => x.Created),
+    async id =
+    {
+        var reference = await _dbContext.Users.FindAsync(int.Parse(id));
+        if (reference == null)
+        {
+            // Throw a custom exception which will be captured by some middleware to process.
+            throw new MyKeysetPaginationReferenceIsNullException();
+        }
+        return reference;
+    };
+```
+
 ## Query model as an argument
 
 All methods also have overloads that accept the pagination query model directly as an argument, as opposed to parsing it from the request query.

samples/Basic/Pages/Index.cshtml.cs

@@ -21,6 +21,7 @@ public IndexModel(
 
 		public async Task OnGet()
 		{
+#nullable enable
 			var query = _dbContext.Users;
 
 			Users = await _paginationService.KeysetPaginateAsync(

samples/Basic/Pages/Keyset2.cshtml.cs

@@ -27,6 +27,7 @@ public Keyset2Model(
 
 		public async Task OnGet()
 		{
+#nullable enable
 			var query = _dbContext.Users;
 
 			Users = await _paginationService.KeysetPaginateAsync(

samples/Basic/Pages/Keyset3.cshtml.cs

@@ -21,6 +21,7 @@ public Keyset3Model(
 
 		public async Task OnGet()
 		{
+#nullable enable
 			var query = _dbContext.Posts;
 
 			Posts = await _paginationService.KeysetPaginateAsync(

src/MR.AspNetCore.Pagination/PaginationService.cs

@@ -24,7 +24,7 @@ public interface IPaginationService
 	Task<KeysetPaginationResult<TOut>> KeysetPaginateAsync<T, TOut>(
 		IQueryable<T> source,
 		Action<KeysetPaginationBuilder<T>> builderAction,
-		Func<string, Task<T>> getReferenceAsync,
+		Func<string, Task<T?>> getReferenceAsync,
 		Func<IQueryable<T>, IQueryable<TOut>> map,
 		KeysetQueryModel queryModel)
 		where T : class
@@ -44,7 +44,7 @@ Task<KeysetPaginationResult<TOut>> KeysetPaginateAsync<T, TOut>(
 	Task<KeysetPaginationResult<TOut>> KeysetPaginateAsync<T, TOut>(
 		IQueryable<T> source,
 		Action<KeysetPaginationBuilder<T>> builderAction,
-		Func<string, Task<T>> getReferenceAsync,
+		Func<string, Task<T?>> getReferenceAsync,
 		Func<IQueryable<T>, IQueryable<TOut>> map,
 		int? pageSize = null)
 		where T : class
@@ -134,7 +134,7 @@ public static Task<KeysetPaginationResult<T>> KeysetPaginateAsync<T>(
 		this IPaginationService @this,
 		IQueryable<T> source,
 		Action<KeysetPaginationBuilder<T>> builderAction,
-		Func<string, Task<T>> getReferenceAsync,
+		Func<string, Task<T?>> getReferenceAsync,
 		KeysetQueryModel queryModel)
 		where T : class
 		=> @this.KeysetPaginateAsync(source, builderAction, getReferenceAsync, query => query, queryModel);
@@ -153,7 +153,7 @@ public static Task<KeysetPaginationResult<T>> KeysetPaginateAsync<T>(
 		this IPaginationService @this,
 		IQueryable<T> source,
 		Action<KeysetPaginationBuilder<T>> builderAction,
-		Func<string, Task<T>> getReferenceAsync,
+		Func<string, Task<T?>> getReferenceAsync,
 		int? pageSize = null)
 		where T : class
 		=> @this.KeysetPaginateAsync(source, builderAction, getReferenceAsync, query => query, pageSize);
@@ -242,7 +242,7 @@ public PaginationService(
 	public async Task<KeysetPaginationResult<TOut>> KeysetPaginateAsync<T, TOut>(
 		IQueryable<T> source,
 		Action<KeysetPaginationBuilder<T>> builderAction,
-		Func<string, Task<T>> getReferenceAsync,
+		Func<string, Task<T?>> getReferenceAsync,
 		Func<IQueryable<T>, IQueryable<TOut>> map,
 		KeysetQueryModel queryModel)
 		where T : class
@@ -302,7 +302,7 @@ public async Task<KeysetPaginationResult<TOut>> KeysetPaginateAsync<T, TOut>(
 	public Task<KeysetPaginationResult<TOut>> KeysetPaginateAsync<T, TOut>(
 		IQueryable<T> source,
 		Action<KeysetPaginationBuilder<T>> builderAction,
-		Func<string, Task<T>> getReferenceAsync,
+		Func<string, Task<T?>> getReferenceAsync,
 		Func<IQueryable<T>, IQueryable<TOut>> map,
 		int? pageSize = null)
 		where T : class

version.props

@@ -1,5 +1,5 @@
 <Project>
   <PropertyGroup>
-    <VersionPrefix>2.0.0</VersionPrefix>
+    <VersionPrefix>2.0.1</VersionPrefix>
   </PropertyGroup>
 </Project>