Parsing nested $filter in $expand fails if request path does not have a navigation source.

[habbes]

Describe the bug

Let's say you have a schema with a top-level unbound function import that does not have an entity set path, the function is composable and returns a collection of entities (but not bound to an entity set).

If you make a request to the function, then query the results using a nested $filter inside an $expand query option like so:

GET /GetActiveCustomers()?$expand=Orders($filter=TotalPrice gt 1000)

You'll get an exception like the following

System.ArgumentNullException: Value cannot be null. (Parameter 'initialState')
ExceptionUtils.CheckArgumentNotNull[T](T value, String parameterName)
MetadataBinder.ctor(BindingState initialState)
SelectExpandBinder.BuildNewMetadataBinder(ODataUriParserConfiguration config, IEdmNavigationSource resourcePathNavigationSource, IEdmNavigationSource targetNavigationSource, IEdmTypeReference elementType, HashSet`1 generatedProperties, Boolean collapsed)
SelectExpandBinder.BindFilter(QueryToken filterToken, IEdmNavigationSource resourcePathNavigationSource, IEdmNavigationSource targetNavigationSource, IEdmTypeReference elementType, HashSet`1 generatedProperties, Boolean collapsed)
SelectExpandBinder.GenerateExpandItem(ExpandTermToken tokenIn)
SelectEnumerableIterator`2.MoveNext()
WhereEnumerableIterator`1.MoveNext()
List`1.AddRange(IEnumerable`1 collection)
SelectExpandBinder.Bind(ExpandToken expandToken, SelectToken selectToken)
SelectExpandSemanticBinder.Bind(ODataPathInfo odataPathInfo, ExpandToken expandToken, SelectToken selectToken, ODataUriParserConfiguration configuration, BindingState state)
ODataQueryOptionParser.ParseSelectAndExpandImplementation(String select, String expand, ODataUriParserConfiguration configuration, ODataPathInfo odataPathInfo)
ODataQueryOptionParser.ParseSelectAndExpand()
ODataUriParser.ParseSelectAndExpand()

Here's the culprit

Seems like it's caused by the resourcePathNavigationSource being null, causing CreateBindingState returning null, which causes the MetadataBinder constructor to throw the argument null exception.

PS: This also seems to affect nested $orderby.

Assemblies affected

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Steps to Reproduce

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Expected behaviour

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Actual behaviour

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Additional details

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[mikepizzo]

OData likes to know the container for any entity being written, in order to be able to generate ids and links, and know where to update any cached versions of the data.

However, there are some cases where we can't identify the container, for example:

1. When there is no navigation property binding for a non-containment navigation property
   a. the related entities may come from different entity sets
   b. the related entities are contained in a containment navigation property, and an ancestor in the containment path is multi-valued
2. Where the entities are returned from a function and there is no entityset path, either because
   a. there is no path from the binding parameter to the collection containing the returned entities
   b. the entities don't come from a single entity set/containment collection
   c. the entities are transient (don't existing in any entity set/containment collection)
   d. the entities have no key values

A common scenario we run into (this issue) is 2)c. -- the case where a function returns entities (they have keys) but they are manufactured by the function and don't exist in an entity container. In this case, the service should be able to support /myNs.function()/key to return an individual instance from the computed result, but there is no navigation source (and thus no canonical url). In this case, for functions, you could consider the function with the key values appended to be the canonical url.

We should support functions/actions that return entities that have no container:
-if a function with no entity set path returns entities that have non-null key values, then myNs.function({params}) should be treated as the navigation source
-if an action or function with no entity set path has null key values, it has no navigation source and its @odata.id (whether written or not) is null. in this case, the contextUrl should just be the type.

An action with no entity set path should still be allowed to return non-null key values, but we can't generate read URLs using the action as the entity container portion of the URL since actions are invoked with GET, are non-composable, and may have side-effects. Thus, we should probably just consider the @odata.id as null for this case as well (and not try to generate any links).

[mikepizzo]

See oasis-tcs/odata-specs#376.