Add dollar levels support in webapi

OData/src/System.Web.OData/OData/EnableQueryAttribute.cs

@@ -543,6 +543,12 @@ private object ExecuteQuery(object response, HttpRequestMessage request, HttpAct
                 elementClrType,
                 request.ODataProperties().Path);
             ODataQueryOptions queryOptions = new ODataQueryOptions(queryContext, request);
+
+            if (queryOptions.SelectExpand != null)
+            {
+                queryOptions.SelectExpand.LevelsMaxLiteralExpansionDepth = _validationSettings.MaxExpansionDepth;
+            }
+
             ValidateQuery(request, queryOptions);
 
             // apply the query

OData/src/System.Web.OData/OData/Query/ODataQueryOptions.cs

@@ -18,6 +18,7 @@
 using System.Web.OData.Query.Validators;
 using Microsoft.OData.Core;
 using Microsoft.OData.Core.UriParser;
+using Microsoft.OData.Core.UriParser.Semantic;
 using Microsoft.OData.Edm;
 
 namespace System.Web.OData.Query
@@ -284,8 +285,15 @@ public virtual IQueryable ApplyTo(IQueryable query, ODataQuerySettings querySett
 
             if (SelectExpand != null)
             {
-                Request.ODataProperties().SelectExpandClause = SelectExpand.SelectExpandClause;
-                result = SelectExpand.ApplyTo(result, querySettings);
+                SelectExpandClause processedClause = SelectExpand.ProcessLevels();
+                SelectExpandQueryOption newSelectExpand = new SelectExpandQueryOption(
+                    SelectExpand.RawSelect,
+                    SelectExpand.RawExpand,
+                    SelectExpand.Context,
+                    processedClause);
+
+                Request.ODataProperties().SelectExpandClause = processedClause;
+                result = newSelectExpand.ApplyTo(result, querySettings);
             }
 
             if (querySettings.PageSize.HasValue)
@@ -328,8 +336,15 @@ public virtual object ApplyTo(object entity, ODataQuerySettings querySettings)
 
             if (SelectExpand != null)
             {
-                Request.ODataProperties().SelectExpandClause = SelectExpand.SelectExpandClause;
-                return SelectExpand.ApplyTo(entity, querySettings);
+                SelectExpandClause processedClause = SelectExpand.ProcessLevels();
+                SelectExpandQueryOption newSelectExpand = new SelectExpandQueryOption(
+                    SelectExpand.RawSelect,
+                    SelectExpand.RawExpand,
+                    SelectExpand.Context,
+                    processedClause);
+
+                Request.ODataProperties().SelectExpandClause = processedClause;
+                return newSelectExpand.ApplyTo(entity, querySettings);
             }
 
             return entity;

OData/src/System.Web.OData/OData/Query/ODataValidationSettings.cs

@@ -16,6 +16,7 @@ public class ODataValidationSettings
         private const int MinMaxNodeCount = 1;
         private const int MinMaxAnyAllExpressionDepth = 1;
         private const int MinMaxOrderByNodeCount = 1;
+        internal const int DefaultMaxExpansionDepth = 2;
 
         private AllowedArithmeticOperators _allowedArithmeticOperators = AllowedArithmeticOperators.All;
         private AllowedFunctions _allowedFunctions = AllowedFunctions.AllFunctions;
@@ -26,7 +27,7 @@ public class ODataValidationSettings
         private int? _maxTop;
         private int _maxAnyAllExpressionDepth = 1;
         private int _maxNodeCount = 100;
-        private int _maxExpansionDepth = 2;
+        private int _maxExpansionDepth = DefaultMaxExpansionDepth;
         private int _maxOrderByNodeCount = 5;
 
         /// <summary>

OData/src/System.Web.OData/OData/Query/SelectExpandQueryOption.cs

@@ -2,6 +2,7 @@
 
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.Contracts;
 using System.Linq;
 using System.Web.Http;
 using System.Web.OData.Properties;
@@ -20,6 +21,7 @@ public class SelectExpandQueryOption
     {
         private SelectExpandClause _selectExpandClause;
         private ODataQueryOptionParser _queryOptionParser;
+        private int _levelsMaxLiteralExpansionDepth = ODataValidationSettings.DefaultMaxExpansionDepth;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="SelectExpandQueryOption"/> class.
@@ -59,6 +61,16 @@ public SelectExpandQueryOption(string select, string expand, ODataQueryContext c
             _queryOptionParser = queryOptionParser;
         }
 
+        internal SelectExpandQueryOption(
+            string select,
+            string expand,
+            ODataQueryContext context,
+            SelectExpandClause selectExpandClause)
+            : this(select, expand, context)
+        {
+            _selectExpandClause = selectExpandClause;
+        }
+
         // This constructor is intended for unit testing only.
         internal SelectExpandQueryOption(string select, string expand, ODataQueryContext context)
         {
@@ -125,6 +137,32 @@ public SelectExpandClause SelectExpandClause
             }
         }
 
+        /// <summary>
+        /// Gets or sets the number of levels that a top level $expand=NavigationProperty($levels=max)
+        /// will be expanded.
+        /// This value will decrease by one with each nesting level in the $expand clause.
+        /// For example, with a property value 5, the following query $expand=A($expand=B($expand=C($levels=max)))
+        /// will be interpreted as $expand=A($expand=B($expand=C($levels=3))).
+        /// If the query gets validated, the <see cref="ODataValidationSettings.MaxExpansionDepth"/> value
+        /// must be greater than or equal to this value.
+        /// </summary>
+        public int LevelsMaxLiteralExpansionDepth
+        {
+            get
+            {
+                return _levelsMaxLiteralExpansionDepth;
+            }
+            set
+            {
+                if (value < 0)
+                {
+                    throw Error.ArgumentMustBeGreaterThanOrEqualTo("LevelsMaxLiteralExpansionDepth", value, 0);
+                }
+
+                _levelsMaxLiteralExpansionDepth = value;
+            }
+        }
+
         /// <summary>
         /// Applies the $select and $expand query options to the given <see cref="IQueryable"/> using the given
         /// <see cref="ODataQuerySettings"/>.
@@ -207,5 +245,155 @@ public void Validate(ODataValidationSettings validationSettings)
                 Validator.Validate(this, validationSettings);
             }
         }
+
+        internal SelectExpandClause ProcessLevels()
+        {
+            bool levelsEncountered;
+            return ProcessLevels(SelectExpandClause, LevelsMaxLiteralExpansionDepth, out levelsEncountered);
+        }
+
+        // Process $levels in SelectExpandClause.
+        private static SelectExpandClause ProcessLevels(
+            SelectExpandClause selectExpandClause,
+            int levelsMaxLiteralExpansionDepth,
+            out bool levelsEncountered)
+        {
+            levelsEncountered = false;
+
+            if (selectExpandClause == null)
+            {
+                return null;
+            }
+
+            // Process $levels in SelectItems of SelectExpandClause.
+            IEnumerable<SelectItem> selectItems = ProcessLevels(
+                selectExpandClause.SelectedItems,
+                levelsMaxLiteralExpansionDepth,
+                out levelsEncountered);
+
+            if (levelsEncountered)
+            {
+                return new SelectExpandClause(selectItems, selectExpandClause.AllSelected);
+            }
+            else
+            {
+                // Return the original SelectExpandClause if no $levels is found.
+                return selectExpandClause;
+            }
+        }
+
+        // Process $levels in SelectedItems.
+        private static IEnumerable<SelectItem> ProcessLevels(
+            IEnumerable<SelectItem> selectItems,
+            int levelsMaxLiteralExpansionDepth,
+            out bool levelsEncountered)
+        {
+            levelsEncountered = false;
+            IList<SelectItem> items = new List<SelectItem>();
+
+            foreach (SelectItem selectItem in selectItems)
+            {
+                ExpandedNavigationSelectItem item = selectItem as ExpandedNavigationSelectItem;
+
+                if (item == null)
+                {
+                    // There is no $levels in non-ExpandedNavigationSelectItem.
+                    items.Add(selectItem);
+                }
+                else
+                {
+                    bool levelsEncouteredInExpand;
+                    // Process $levels in ExpandedNavigationSelectItem.
+                    ExpandedNavigationSelectItem expandItem = ProcessLevels(
+                        item,
+                        levelsMaxLiteralExpansionDepth,
+                        out levelsEncouteredInExpand);
+                    levelsEncountered = levelsEncountered || levelsEncouteredInExpand;
+
+                    if (expandItem != null)
+                    {
+                        items.Add(expandItem);
+                    }
+                }
+            }
+
+            return items;
+        }
+
+        // Process $levels in ExpandedNavigationSelectItem.
+        private static ExpandedNavigationSelectItem ProcessLevels(
+            ExpandedNavigationSelectItem expandItem,
+            int levelsMaxLiteralExpansionDepth,
+            out bool levelsEncounteredInExpand)
+        {
+            // Call ProcessLevels on SelectExpandClause recursively.
+            SelectExpandClause selectExpandClause = ProcessLevels(
+                expandItem.SelectAndExpand,
+                levelsMaxLiteralExpansionDepth - 1,
+                out levelsEncounteredInExpand);
+
+            if (expandItem.LevelsOption == null)
+            {
+                if (levelsEncounteredInExpand)
+                {
+                    return new ExpandedNavigationSelectItem(
+                        expandItem.PathToNavigationProperty,
+                        expandItem.NavigationSource,
+                        selectExpandClause);
+                }
+                else
+                {
+                    // Return the original ExpandedNavigationSelectItem if no $levels is found.
+                    return expandItem;
+                }
+            }
+
+            // There is $levels in current ExpandedNavigationSelectItem.
+            levelsEncounteredInExpand = true;
+            int level = expandItem.LevelsOption.IsMaxLevel ?
+                levelsMaxLiteralExpansionDepth :
+                (int)expandItem.LevelsOption.Level;
+
+            if (level <= 0)
+            {
+                // Do not expand if $levels is equal to 0.
+                return null;
+            }
+
+            // Initialize current SelectExpandClause with processed SelectExpandClause.
+            SelectExpandClause currentSelectExpandClause = selectExpandClause;
+            ExpandedNavigationSelectItem item = null;
+
+            // Construct new ExpandedNavigationSelectItem with recursive expansion.
+            while (level > 0)
+            {
+                // Construct a new ExpandedNavigationSelectItem with current SelectExpandClause.
+                item = new ExpandedNavigationSelectItem(
+                    expandItem.PathToNavigationProperty,
+                    expandItem.NavigationSource,
+                    currentSelectExpandClause);
+
+                // Update current SelectExpandClause with the new ExpandedNavigationSelectItem.
+                if (selectExpandClause.AllSelected)
+                {
+                    currentSelectExpandClause = new SelectExpandClause(
+                        new[] { item }.Concat(selectExpandClause.SelectedItems),
+                        selectExpandClause.AllSelected);
+                }
+                else
+                {
+                    // PathSelectItem is needed for the expanded item if AllSelected is false. 
+                    PathSelectItem pathSelectItem = new PathSelectItem(
+                        new ODataSelectPath(expandItem.PathToNavigationProperty));
+                    currentSelectExpandClause = new SelectExpandClause(
+                        new SelectItem[] { item, pathSelectItem }.Concat(selectExpandClause.SelectedItems),
+                        selectExpandClause.AllSelected);
+                }
+
+                level--;
+            }
+
+            return item;
+        }
     }
 }

OData/src/System.Web.OData/OData/Query/Validators/SelectExpandQueryValidator.cs

@@ -38,6 +38,14 @@ public virtual void Validate(SelectExpandQueryOption selectExpandQueryOption, OD
 
             if (validationSettings.MaxExpansionDepth > 0)
             {
+                if (selectExpandQueryOption.LevelsMaxLiteralExpansionDepth > validationSettings.MaxExpansionDepth)
+                {
+                    throw new ODataException(Error.Format(
+                        SRResources.InvalidExpansionDepthValue,
+                        "LevelsMaxLiteralExpansionDepth",
+                        "MaxExpansionDepth"));
+                }
+
                 ValidateDepth(selectExpandQueryOption.SelectExpandClause, validationSettings.MaxExpansionDepth);
             }
         }
@@ -54,15 +62,34 @@ private static void ValidateDepth(SelectExpandClause selectExpand, int maxDepth)
                 SelectExpandClause currentNode = tuple.Item2;
 
                 ExpandedNavigationSelectItem[] expandItems = currentNode.SelectedItems.OfType<ExpandedNavigationSelectItem>().ToArray();
-                if (expandItems.Length > 0 && currentDepth == maxDepth)
+
+                if (expandItems.Length > 0 &&
+                    ((currentDepth == maxDepth &&
+                    expandItems.Any(expandItem =>
+                        expandItem.LevelsOption == null ||
+                        expandItem.LevelsOption.IsMaxLevel ||
+                        expandItem.LevelsOption.Level != 0)) ||
+                    expandItems.Any(expandItem =>
+                        expandItem.LevelsOption != null &&
+                        !expandItem.LevelsOption.IsMaxLevel &&
+                        (expandItem.LevelsOption.Level > Int32.MaxValue ||
+                        expandItem.LevelsOption.Level + currentDepth > maxDepth))))
                 {
                     throw new ODataException(
                         Error.Format(SRResources.MaxExpandDepthExceeded, maxDepth, "MaxExpansionDepth"));
                 }
 
                 foreach (ExpandedNavigationSelectItem expandItem in expandItems)
                 {
-                    nodesToVisit.Push(Tuple.Create(currentDepth + 1, expandItem.SelectAndExpand));
+                    int depth = currentDepth + 1;
+
+                    if (expandItem.LevelsOption != null && !expandItem.LevelsOption.IsMaxLevel)
+                    {
+                        // Add the value of $levels for next depth.
+                        depth = depth + (int)expandItem.LevelsOption.Level - 1;
+                    }
+
+                    nodesToVisit.Push(Tuple.Create(depth, expandItem.SelectAndExpand));
                 }
             }
         }

OData/src/System.Web.OData/Properties/SRResources.resx

@@ -535,6 +535,9 @@
   <data name="BatchRequestMissingContent" xml:space="preserve">
     <value>The 'Content' property on the batch request cannot be null.</value>
   </data>
+  <data name="InvalidExpansionDepthValue" xml:space="preserve">
+    <value>'{0}' should be less than or equal to '{1}'.</value>
+  </data>
   <data name="MaxExpandDepthExceeded" xml:space="preserve">
     <value>The request includes a $expand path which is too deep. The maximum depth allowed is {0}. To increase the limit, set the '{1}' property on EnableQueryAttribute or ODataValidationSettings.</value>
   </data>