Added fields as query parameter

Saule/Constants.cs

@@ -19,6 +19,7 @@ public static class QueryNames
             public const string Sorting = "sort";
             public const string Filtering = "filter";
             public const string Including = "include";
+            public const string Fieldset = "fields";
         }
 
         public static class QueryValues

Saule/Http/AllowsQueryAttribute.cs

@@ -3,6 +3,7 @@
 using System.Net.Http;
 using System.Web.Http.Controllers;
 using System.Web.Http.Filters;
+using Saule.Queries.Fieldset;
 using Saule.Queries.Filtering;
 using Saule.Queries.Including;
 using Saule.Queries.Sorting;
@@ -28,6 +29,7 @@ public override void OnActionExecuting(HttpActionContext actionContext)
 
             queryContext.Sort = new SortContext(queryParams);
             queryContext.Filter = new FilterContext(queryParams);
+            queryContext.Fieldset = new FieldsetContext(queryParams);
 
             if (queryContext.Include == null)
             {

Saule/JsonApiSerializer.cs

@@ -78,7 +78,8 @@ public PreprocessResult PreprocessContent(object @object, ApiResource resource,
                         propertyNameConverter: config.PropertyNameConverter,
                         urlBuilder: UrlPathBuilder,
                         paginationContext: QueryContext?.Pagination,
-                        includeContext: QueryContext?.Include);
+                        includeContext: QueryContext?.Include,
+                        fieldsetContext: QueryContext?.Fieldset);
             }
             catch (Exception ex)
             {

Saule/JsonApiSerializerOfT.cs

@@ -7,6 +7,7 @@
 using Newtonsoft.Json.Linq;
 using Saule.Http;
 using Saule.Queries;
+using Saule.Queries.Fieldset;
 using Saule.Queries.Filtering;
 using Saule.Queries.Including;
 using Saule.Queries.Pagination;
@@ -130,6 +131,7 @@ private QueryContext GetQueryContext(IEnumerable<KeyValuePair<string, string>> f
                 context.Sort = new SortContext(keyValuePairs);
                 context.Filter = new FilterContext(keyValuePairs) { QueryFilters = QueryFilterExpressions };
                 context.Include = new IncludeContext(keyValuePairs);
+                context.Fieldset = new FieldsetContext(keyValuePairs);
             }
 
             return context;

Saule/Queries/Fieldset/FieldsetContext.cs

@@ -0,0 +1,36 @@
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Saule.Queries.Fieldset
+{
+    /// <summary>
+    /// Context for fieldset operations
+    /// </summary>
+    public class FieldsetContext
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="FieldsetContext"/> class.
+        /// </summary>
+        /// <param name="queryParams">query string that might contain Fieldset keyword</param>
+        public FieldsetContext(IEnumerable<KeyValuePair<string, string>> queryParams)
+        {
+            Properties =
+                from query in queryParams
+                where query.Key.StartsWith(Constants.QueryNames.Fieldset)
+                let type = query.Key.Substring(Constants.QueryNames.Fieldset.Length + 1)
+                let fields = query.Value.Split(',')
+                select new FieldsetProperty(type, fields);
+        }
+
+        /// <summary>
+        /// Gets including properties
+        /// </summary>
+        public IEnumerable<FieldsetProperty> Properties { get; internal set; }
+
+        /// <inheritdoc/>
+        public override string ToString()
+        {
+            return Properties != null && Properties.Any() ? string.Join("&", Properties.Select(p => p.ToString())) : string.Empty;
+        }
+    }
+}

Saule/Queries/Fieldset/FieldsetProperty.cs

@@ -0,0 +1,35 @@
+namespace Saule.Queries.Fieldset
+{
+    /// <summary>
+    /// Property for fieldset
+    /// </summary>
+    public class FieldsetProperty
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="FieldsetProperty"/> class.
+        /// </summary>
+        /// <param name="type">type for field filter</param>
+        /// <param name="fields">fields to serialize filter</param>
+        public FieldsetProperty(string type, string[] fields)
+        {
+            Type = type;
+            Fields = fields;
+        }
+
+        /// <summary>
+        /// Gets property type
+        /// </summary>
+        public string Type { get; }
+
+        /// <summary>
+        /// Gets property fields
+        /// </summary>
+        public string[] Fields { get; }
+
+        /// <inheritdoc/>
+        public override string ToString()
+        {
+            return $"fields[{Type}]={string.Join(",", Fields)}";
+        }
+    }
+}

Saule/Queries/QueryContext.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using Saule.Queries.Fieldset;
 using Saule.Queries.Filtering;
 using Saule.Queries.Including;
 using Saule.Queries.Pagination;
@@ -33,6 +34,11 @@ public class QueryContext
         /// </summary>
         public IncludeContext Include { get; internal set; }
 
+        /// <summary>
+        /// Gets include context
+        /// </summary>
+        public FieldsetContext Fieldset { get; internal set; }
+
         /// <summary>
         /// Gets or sets a value indicating whether that query parameters
         /// will be handled by action itself or Saule should handle them
@@ -47,7 +53,8 @@ public override string ToString()
                 Pagination?.ToString(),
                 Sort?.ToString(),
                 Filter?.ToString(),
-                Include?.ToString()
+                Include?.ToString(),
+                Fieldset?.ToString()
             };
 
             return string.Join("&", result.Where(c => !string.IsNullOrEmpty(c)));

Saule/Saule.csproj

@@ -70,6 +70,8 @@
     <Compile Include="Http\JsonApiQueryValueProvider.cs" />
     <Compile Include="Http\JsonApiQueryValueProviderFactory.cs" />
     <Compile Include="JsonApiSerializerOfT.cs" />
+    <Compile Include="Queries\Fieldset\FieldsetContext.cs" />
+    <Compile Include="Queries\Fieldset\FieldsetProperty.cs" />
     <Compile Include="Serialization\CamelCasePropertyNameConverter.cs" />
     <Compile Include="Serialization\DefaultPropertyNameConverter.cs" />
     <Compile Include="Serialization\IPropertyNameConverter.cs" />

Saule/Serialization/ResourceSerializer.cs

@@ -4,6 +4,7 @@
 using System.Linq;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
+using Saule.Queries.Fieldset;
 using Saule.Queries.Including;
 using Saule.Queries.Pagination;
 
@@ -14,6 +15,7 @@ internal class ResourceSerializer
         private readonly Uri _baseUrl;
         private readonly PaginationContext _paginationContext;
         private readonly IncludeContext _includeContext;
+        private readonly FieldsetContext _fieldsetContext;
         private readonly ApiResource _resource;
         private readonly object _value;
         private readonly IPropertyNameConverter _propertyNameConverter;
@@ -28,6 +30,7 @@ public ResourceSerializer(
             IUrlPathBuilder urlBuilder,
             PaginationContext paginationContext,
             IncludeContext includeContext,
+            FieldsetContext fieldsetContext,
             IPropertyNameConverter propertyNameConverter = null)
         {
             _propertyNameConverter = propertyNameConverter ?? new DefaultPropertyNameConverter();
@@ -37,6 +40,7 @@ public ResourceSerializer(
             _baseUrl = baseUrl;
             _paginationContext = paginationContext;
             _includeContext = includeContext;
+            _fieldsetContext = fieldsetContext;
             _includedGraphPaths = IncludedGraphPathsFromContext(includeContext);
         }
 
@@ -248,7 +252,17 @@ private JObject SerializeNode(ResourceGraphNode node, bool isCollection)
                 }
             }
 
-            var attributes = SerializeAttributes(node);
+            JObject attributes = null;
+            if (_fieldsetContext != null && _fieldsetContext.Properties.Count(property => property.Type == node.Key.Type) > 0)
+            {
+                FieldsetProperty fieldset = _fieldsetContext.Properties.Where(property => property.Type == node.Key.Type).First();
+                attributes = SerializeAttributes(node, fieldset);
+            }
+            else
+            {
+                attributes = SerializeAttributes(node);
+            }
+
             if (attributes != null)
             {
                 response["attributes"] = attributes;
@@ -281,6 +295,24 @@ private JObject SerializeAttributes(ResourceGraphNode node)
             return JObject.FromObject(attributeHash, _serializer);
         }
 
+        private JObject SerializeAttributes(ResourceGraphNode node, FieldsetProperty fieldset)
+        {
+            var attributeHash = node.Resource.Attributes
+                .Where(a =>
+                    node.SourceObject.IncludesProperty(_propertyNameConverter.ToModelPropertyName(a.InternalName)) && fieldset.Fields.Contains(_propertyNameConverter.ToModelPropertyName(a.InternalName)))
+                .Select(a =>
+                    new
+                    {
+                        Key = _propertyNameConverter.ToJsonPropertyName(a.InternalName),
+                        Value = node.SourceObject.GetValueOfProperty(_propertyNameConverter.ToModelPropertyName(a.InternalName))
+                    })
+                .ToDictionary(
+                    kvp => kvp.Key,
+                    kvp => kvp.Value);
+
+            return JObject.FromObject(attributeHash, _serializer);
+        }
+
         private JObject SerializeRelationships(ResourceGraphNode node)
         {
             if (node.Relationships.Count == 0)

Tests/JsonApiSerializerTests.cs

@@ -68,6 +68,36 @@ public void ConditionallyAppliesFilters()
 
         }
 
+        [Fact(DisplayName = "Uses query fieldset expressions if specified")]
+        public void UsesQueryFieldsetExpressions()
+        {
+            var target = new JsonApiSerializer<CompanyResource>
+            {
+                AllowQuery = true
+            };
+            var companies = Get.Companies(1).ToList();
+            var result = target.Serialize(companies, new Uri(DefaultUrl, "?fields[corporation]=Name,Location"));
+            _output.WriteLine(result.ToString());
+
+            Assert.NotNull(result["data"][0]["attributes"]["name"]);
+            Assert.NotNull(result["data"][0]["attributes"]["location"]);
+            Assert.Null(result["data"][0]["attributes"]["number-of-employees"]);
+        }
+
+        [Fact(DisplayName = "Returns no fields if requested field is not part of that model")]
+        public void ReturnEmptyModelForUnknownFieldsetExpressions()
+        {
+            var target = new JsonApiSerializer<CompanyResource>
+            {
+                AllowQuery = true
+            };
+            var companies = Get.Companies(1).ToList();
+            var result = target.Serialize(companies, new Uri(DefaultUrl, "?fields[corporation]=Notafield"));
+            _output.WriteLine(result.ToString());
+
+            Assert.False(((JToken)result["data"][0]["attributes"]).HasValues);
+        }
+
         [Fact(DisplayName = "Does not allow null Uri")]
         public void HasAContract()
         {

Tests/Serialization/MetadataTests.cs

@@ -36,7 +36,7 @@ public void SerializesObjectsCorrectly()
                 new Uri("http://localhost/people/123"),
                 new DefaultUrlPathBuilder(),
                 null,
-                null);
+                null, null);
 
             var result = target.Serialize();
             _output.WriteLine(result.ToString());
@@ -67,7 +67,7 @@ public void SerializesDictionariesCorrectly()
                 new Uri("http://localhost/people/123"),
                 new DefaultUrlPathBuilder(),
                 null,
-                null);
+                null, null);
 
             var result = target.Serialize();
             _output.WriteLine(result.ToString());
@@ -95,7 +95,7 @@ public void PassesThroughJTokens()
                 new Uri("http://localhost/people/123"),
                 new DefaultUrlPathBuilder(),
                 null,
-                null);
+                null, null);
 
             var result = target.Serialize();
             _output.WriteLine(result.ToString());
@@ -121,7 +121,7 @@ public void SerializesCollectionsCorrectly()
                 new Uri("http://localhost/people/123"),
                 new DefaultUrlPathBuilder(),
                 null,
-                null);
+                null, null);
 
             var result = target.Serialize();
             _output.WriteLine(result.ToString());
@@ -146,7 +146,7 @@ public void CallsGetMetadataForCorrectly()
                 new Uri("http://localhost/people/123"),
                 new DefaultUrlPathBuilder(),
                 null,
-                null);
+                null, null);
 
             target.Serialize();
 
@@ -160,7 +160,7 @@ public void CallsGetMetadataForCorrectly()
                 new Uri("http://localhost/people/123"),
                 new DefaultUrlPathBuilder(),
                 null,
-                null);
+                null, null);
 
             target.Serialize();
 
@@ -178,7 +178,7 @@ public void EmptyForNull()
                 new Uri("http://localhost/people/123"),
                 new DefaultUrlPathBuilder(),
                 null,
-                null);
+                null, null);
 
             var result = target.Serialize();
             _output.WriteLine(result.ToString());

Tests/Serialization/ResourceDeserializerTests.cs

@@ -25,10 +25,10 @@ public ResourceDeserializerTests()
             _people = Get.People(5).ToArray();
             var singleSerializer = new ResourceSerializer(
             _person, new PersonResource(), new Uri("http://example.com/people/1"),
-            new DefaultUrlPathBuilder(), null, null);
+            new DefaultUrlPathBuilder(), null, null, null);
             var multiSerializer = new ResourceSerializer(
                 _people, new PersonResource(), new Uri("http://example.com/people/"),
-                new DefaultUrlPathBuilder(), null, null);
+                new DefaultUrlPathBuilder(), null, null, null);
 
             _singleJson = JToken.Parse(singleSerializer.Serialize().ToString());
             _collectionJson = JToken.Parse(multiSerializer.Serialize().ToString());
@@ -53,7 +53,7 @@ public void DeserializesCamelCase()
 
             var singleSerializer = new ResourceSerializer(
                 _person, new PersonResource(), new Uri("http://example.com/people/1"),
-                new DefaultUrlPathBuilder(), null, null, camelCasePropertyNameConverter);
+                new DefaultUrlPathBuilder(), null, null, null, camelCasePropertyNameConverter);
 
             var singleJson = JToken.Parse(singleSerializer.Serialize().ToString());