fix: #641

src/JsonApiDotNetCore/QueryParameterServices/Contracts/IPageService.cs

@@ -6,13 +6,17 @@ namespace JsonApiDotNetCore.Query
     public interface IPageService : IQueryParameterService
     {
         /// <summary>
-        /// What the total records are for this output
+        /// Gets the requested or default page size
         /// </summary>
-        int? TotalRecords { get; set; }
+        int CurrentPageSize { get; }
+        /// <summary>
+        /// Default size to be used in pagination
+        /// </summary>
+        int DefaultPageSize { get; set; }
         /// <summary>
-        /// How many records per page should be shown
+        /// Currently requested page size to be used in pagination
         /// </summary>
-        int PageSize { get; set; }
+        int? RequestedPageSize { get; set; }
         /// <summary>
         /// The page requested. Note that the page number is one-based.
         /// </summary>
@@ -29,5 +33,9 @@ public interface IPageService : IQueryParameterService
         /// Denotes if pagination is backwards
         /// </summary>
         bool Backwards { get; }
+        /// <summary>
+        /// What the total records are for this output
+        /// </summary>
+        int? TotalRecords { get; set; }
     }
 }

src/JsonApiDotNetCore/QueryParameterServices/PageService.cs

@@ -13,11 +13,10 @@ namespace JsonApiDotNetCore.Query
     public class PageService : QueryParameterService, IPageService
     {
         private readonly IJsonApiOptions _options;
-
         public PageService(IJsonApiOptions options, IResourceGraph resourceGraph, ICurrentRequest currentRequest) : base(resourceGraph, currentRequest)
         {
             _options = options;
-            PageSize = _options.DefaultPageSize;
+            DefaultPageSize = _options.DefaultPageSize;
         }
 
         /// <summary>
@@ -26,14 +25,27 @@ public PageService(IJsonApiOptions options, IResourceGraph resourceGraph, ICurre
         internal PageService(IJsonApiOptions options)
         {
             _options = options;
-            PageSize = _options.DefaultPageSize;
+            DefaultPageSize = _options.DefaultPageSize;
         }
 
         /// <inheritdoc/>
-        public int? TotalRecords { get; set; }
+        public int CurrentPageSize
+        {
+            get
+            {
+                if (RequestedPageSize.HasValue)
+                {
+                    return RequestedPageSize.Value;
+                }
+                return DefaultPageSize;
+            }
+        }
+
+        /// <inheritdoc/>
+        public int DefaultPageSize { get; set; }
 
         /// <inheritdoc/>
-        public int PageSize { get; set; }
+        public int? RequestedPageSize { get; set; }
 
         /// <inheritdoc/>
         public int CurrentPage { get; set; } = 1;
@@ -42,17 +54,20 @@ internal PageService(IJsonApiOptions options)
         public bool Backwards { get; set; }
 
         /// <inheritdoc/>
-        public int TotalPages => (TotalRecords == null || PageSize == 0) ? -1 : (int)Math.Ceiling(decimal.Divide(TotalRecords.Value, PageSize));
+        public int TotalPages => (TotalRecords == null || CurrentPageSize == 0) ? -1 : (int)Math.Ceiling(decimal.Divide(TotalRecords.Value, CurrentPageSize));
 
         /// <inheritdoc/>
         public bool CanPaginate { get { return TotalPages > 1; } }
 
+        /// <inheritdoc/>
+        public int? TotalRecords { get; set; }
+
         /// <inheritdoc/>
         public virtual void Parse(KeyValuePair<string, StringValues> queryParameter)
         {
             EnsureNoNestedResourceRoute();
             // expected input = page[size]=<integer>
-            //                  page[number]=<integer > 0>
+            //                  page[number]=<integer greater than zero> 
             var propertyName = queryParameter.Key.Split(QueryConstants.OPEN_BRACKET, QueryConstants.CLOSE_BRACKET)[1];
 
             const string SIZE = "size";
@@ -70,7 +85,7 @@ public virtual void Parse(KeyValuePair<string, StringValues> queryParameter)
                 }
                 else
                 {
-                    PageSize = size;
+                    RequestedPageSize = size;
                 }
             }
             else if (propertyName == NUMBER)

src/JsonApiDotNetCore/Serialization/Server/Builders/LinkBuilder.cs

@@ -63,19 +63,19 @@ private void SetPageLinks(ResourceContext primaryResource, TopLevelLinks links)
         {
             if (_pageService.CurrentPage > 1)
             {
-                links.Prev = GetPageLink(primaryResource, _pageService.CurrentPage - 1, _pageService.PageSize);
+                links.Prev = GetPageLink(primaryResource, _pageService.CurrentPage - 1, _pageService.CurrentPageSize);
             }
 
             if (_pageService.CurrentPage < _pageService.TotalPages)
             {
-                links.Next = GetPageLink(primaryResource, _pageService.CurrentPage + 1, _pageService.PageSize);
+                links.Next = GetPageLink(primaryResource, _pageService.CurrentPage + 1, _pageService.CurrentPageSize);
             }
 
             if (_pageService.TotalPages > 0)
             {
-                links.Self = GetPageLink(primaryResource, _pageService.CurrentPage, _pageService.PageSize);
-                links.First = GetPageLink(primaryResource, 1, _pageService.PageSize);
-                links.Last = GetPageLink(primaryResource, _pageService.TotalPages, _pageService.PageSize);
+                links.Self = GetPageLink(primaryResource, _pageService.CurrentPage, _pageService.CurrentPageSize);
+                links.First = GetPageLink(primaryResource, 1, _pageService.CurrentPageSize);
+                links.Last = GetPageLink(primaryResource, _pageService.TotalPages, _pageService.CurrentPageSize);
             }
         }
 

src/JsonApiDotNetCore/Services/DefaultResourceService.cs

@@ -200,7 +200,7 @@ public virtual async Task UpdateRelationshipsAsync(TId id, string relationshipNa
 
         protected virtual async Task<IEnumerable<TResource>> ApplyPageQueryAsync(IQueryable<TResource> entities)
         {
-            if (!(_pageService.PageSize > 0))
+            if (!(_pageService.CurrentPageSize > 0))
             {
                 var allEntities = await _repository.ToListAsync(entities);
                 return allEntities as IEnumerable<TResource>;
@@ -214,10 +214,10 @@ protected virtual async Task<IEnumerable<TResource>> ApplyPageQueryAsync(IQuerya
             if (_logger?.IsEnabled(LogLevel.Information) == true)
             {
                 _logger?.LogInformation($"Applying paging query. Fetching page {pageOffset} " +
-                    $"with {_pageService.PageSize} entities");
+                    $"with {_pageService.CurrentPageSize} entities");
             }
 
-            return await _repository.PageAsync(entities, _pageService.PageSize, pageOffset);
+            return await _repository.PageAsync(entities, _pageService.CurrentPageSize, pageOffset);
         }
 
         /// <summary>

test/UnitTests/Builders/LinkBuilderTests.cs

@@ -195,7 +195,7 @@ private IPageService GetPageManager()
             mock.Setup(m => m.CanPaginate).Returns(true);
             mock.Setup(m => m.CurrentPage).Returns(2);
             mock.Setup(m => m.TotalPages).Returns(3);
-            mock.Setup(m => m.PageSize).Returns(10);
+            mock.Setup(m => m.CurrentPageSize).Returns(10);
             return mock.Object;
 
         }

test/UnitTests/QueryParameters/PageServiceTests.cs

@@ -46,7 +46,7 @@ public void Parse_PageSize_CanParse(string value, int expectedValue, bool should
             else
             {
                 service.Parse(query);
-                Assert.Equal(expectedValue, service.PageSize);
+                Assert.Equal(expectedValue, service.CurrentPageSize);
             }
         }