4.06 Navigation (R8)

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ReSharper navigation consists of two main parts:

  • Context navigation ('Navigate From Here...')
  • Global navigation ('Go To ...')

The navigation framework is fairly pluggable, so in most cases all you need to do is to simply provide your own components. You can implement the following features:

Context Navigation

Context navigation consists of two parts: the searching engine and the user-interaction provider. These two parts are divided into different entities in ReSharper Framework.

Feature Providers

Feature providers represent features themselves. That is, there is just one provider per navigation feature regardless of the number of languages and environments where this feature is supposed to work.

Each context navigation provider implements either the IContextSearchProvider or the INavigateFromHereProvider interface. The IContextSearchProvider interface is defined as follows:

The action that the GetSearchesExecution() method returns is actually the execution of the navigation feature. When this method returns null, it implies that this feature is not available for this data context. The INavigationExecutionHost is a host object which can be used for performing certain UI activities, such as showing a drop-down box or the advanced search dialog.
The INavigateFromHere interface is fairly similar to IContextSearchProvider -- it has just one method that returns navigation execution and additional data for presenting in the 'Navigate From Here' drop-down menu.

If you want your navigation items to appear in the 'Navigate From Here' menu, you have to implement the INavigateFromHereProvider interface.

Binding to an action

You don't need to write any code in your action handler's methods, as all feature logic needs to be written inside navigation providers. All you need to bind your action to a navigation provider is to derive your custom action handler class from ContextNavigationActionBase<TNavigateFromHereProvider> (if you want your action to appear in the 'Navigate From Here' menu) or ContextSearchActionBase<TContextSearchProvider>.
Additionally, your provider should be decorated with the ContextNavigationProvider attribute.

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If you want your feature to appear only in 'Navigate From Here' menu, you don't even have to write an action --- just implement ContextNavigationProvider that implements INavigateFromHereProvider.

If your navigation is not complicated, that's all you need to know about the context navigation framework.

Example

Here is an example of simple navigation to the corresponding folder using Windows explorer.

Context Searches

If your navigation is complicated and works differently in differenent languages then you can use context searches to provide different search results for a specific language.
In this case, your provider needs to be derived from ContextSearchesCollector<TContextSearch> class and all you need is to implement the Execute() method.

IContextSearch is an interface for providers decorated with the FeaturePart attribute and providing specific navigation execution. There are just two methods in this interface, indicating applicability and availability of said context search.

The applicability method is more global and implies that this context search can work for this data context and will override other components it is derived from.
Availability means that for a specific data context this context search is enabled and will be fired.

You can alter the behavior of existing ReSharper navigation features by providing your own context search components. Here is an example of a  context search that extends the 'Go To Implementation' search for XAML:

Global Navigation ('Go To ...')

Global nagivation relates to functionality used in various global searches such as Go To Type or Go To Member. Typically, these searches all function as a text-entry popup box that, when typed into, presents a list that can be further refined and then, upon selection, navigated to the declared element. In addition, lists can ‘morph’ so that a Go To Type search can suddenly become a Go To Symbol search with the press of one shortcut.

Occurence Navigation Provider

In order to provide items for a particular global navigation mechanic, we need to implement an occurence navigation provider -- a class that implements the IOccurenceNavigationProvider interface. The following image illustrates the hierarchy of this interface:

As you can see, the four interface members are self-descriprive, and are further implemented by concrete classes based on language. For example, IGotoSymbolProvider has concrete implementations for the CLR, CSS, HTML and JavaScript. This interface is also implemented by the ClrGotoTypeMemberProvider, which illustrates a kind of inheritance mechanic --- this makes sense because Go To Symbol actually includes information from Go To Type.

The interface is fairly simple, and has only three members:

The first method, FindMatchingInfos(), find matched items and returns a corresponding list of MatchingInfo objects. A MatchingInfo is simply a data class that describes the necessary info used to store a matching item --- its identifier, a set of IdentifierMatch objects (corresponding to the matches, as there can be many) and some other service information.

The second method, GetOccurencesByMatchingInfo, returns a set of occurences given the matching information. An occurence is essentially a pointer to the location where something was found. Since the definition of ‘something’ is quite vague, an occurence can be practically anything --- a range in a text editor, a project reference, a while project or a file. For example, a project file is represented by a ProjectItemOccurence, which in turn references an IProjectItem it points to.

In addition, you are required to implement an interface member inherited from IApplicableGotoProvider:

The above method lets us determine if a particular provider should work in a given context. Providers can theoretically inherit from one another, and if you are overriding an existing provider, instead of working every single time (like a SolutionComponent would), it instead checks the IsApplicable result.

The API now provides you an interface called IGotoEverythingProvider, which happens to inherit these two interfaces and in addition specifies a sorting function declared as

This interface lets you calculate a priority of the displayed element, such that the lower the result gets returned, the higher is the priority of the element.

Now, to create a provider, simply implement the interface and decorate the class with ShellFeaturePart:

Occurence Presenter

Having a set of occurences is great, but they’re useless until presented on-screen. And this is where occurence presenters come in. An occurence presenter is, basically, a class that knows how to present a particular occurence as a menu item. In addition to being decorated by an OccurencePresenter attribute, it is embodied by the IOccurencePresenter interface defined below:

First, there’s the IsApplicable() method. This method determines whether this occurence presenter is applicable for the particular type of occurence. These typically go hand-in-hand, for example:

Then there’s the Present() method, which is called when the IOccurence needs to be presented. The goal of this method is to make assignments to the descriptor parameter. The IMenuItemDescriptor interface is quite large, but the only property we need to concern ourselves with here is Text --- this is a RichText definition that will be displayed as a menu item for this occurence.

Here’s a sample implementation. Note that descriptor.Style must be defined — otherwise, the item will be disabled.

Occurence Kind Provider

When you open up, say, Find Usages, you’ll find that you have an ability to filter information. Some examples are read usages, write usages, attribute references, and so on. Each has its own special icon and an ability to filter it out if necessary.

The types of elements just mentioned are called occurence kinds. Many kinds of occurences can be found as static members of the OccurenceKind class, and new ones can be created. An occurence kind is simply an enum-like class, keeping only two bits of information: its name and whether it is primary or not. If the occurrence kind is set as primary, the Find Results window will always display this kind of occurrence regardless of what filter is set. Other occurrences are non-primary, i.e. they are only displayed when there are occurrences of this occurrence kind (e.g., unit tests).

Now, we can talk about occurence type providers. These are typically solution components (i.e., decorated with the SolutionComponent attributes) that also implement the IOccurenceKindProvider interface. This interface is defined as follows:

The GetAllPossibleOccurenceKinds() method returns a list of all possible occurences that this provider can give in theory. For example, in C# we can yield interface qualifications, base method calls and invocations, whereas in VB we also have the Handles clause.

The GetOccurenceKinds() method returns a collection of occurence kinds (or you can return an EmptyList<OccurenceKind>.InstanceList if there aren’t any) that are applicable for a given occurence. Naturally, this typically assumes that you would try to cast the IOccurence to a concrete type (e.g., ReferenceOccurence) to investigate its contents and yield the occurence kinds accordingly.

Occurence Section Provider

When search results are presented in a dialogue window, they are typically split into sections via horizintal lines. The component that provides information about the different types of section is a FeaturePart that implements the IOccurenceSectionProvider interface. The interface is defined as follows:

Let’s go through the methods. Firstly, IsApplicable() checks whether this section provider is applicable given the type of the occurence browser we are working with. This is typically a simple is call, e.g.:

The second method is GetTreeSections(), and it is this method that returns a set of TreeSection objects specific to this section provider. We’ll discuss the TreeSection structure in a moment, but let’s briefly discuss the third method first. GetGroupSectionId basically lets us determine the groups (there can be more than one) in which a particular IOccurence needs to appear. The default implementation as defined in the OccurenceSectionProvider class (you should inherit from this, rather than implementing the interface by hand) is to use a special method GetSectionId() to pick a known section given the type of the occurence:

Tree Model

Now, let’s go back and talk about TreeSection definitions or, rather, about tree model, since the TreeSection is nothing more than a container class for a title and a TreeModel and it is this tree model that’s of interest to us.

A TreeModel, as you may have guessed, is simply a definition for the classical N-ary tree. The model itself has itself a collection of roots, i.e. a property Roots of type IList<TreeModelNode> as well as variousl mechanisms for insertion, removal and updating of TreeModelNode entities.

Each TreeModelNode in turn has a set of children, who are also TreeModelNode s themselves. Sorting is possible at both the TreeModel and TreeModelNode level. Note that the actual data storage inside the nodes is defined as an object, i.e. is untyped.

It helps to remember that both TreeModel and TreeModelNode are abstract classes, and that you are more likely to be working with their descendants, the most basic of which is TreeSimpleModel.

Occurence

The menu items themselves are simply items which implement the IOccurence interface. This interface defines a rather large number of elements:

This interface is very feature-complete in terms of supporting, e.g., constructs which exist in code. In the case where you are providing ad hoc items not related to the PSI, you can provide the following defaults intead:

  • DumpToString() — up to you, this is a debugging method.
  • TextRange — just return a new TextRange(). You might want to consider making a single instance to return for each query.
  • MergeKey - this yields a key which indicates whether or not several items should be merged. Thus, it makes sense to have this property yield a unique value for each item you don't intend to merge.
  • ProjectElementEnvoy, TypeMember, TypeElement, Namespace, MergedItems – simply return null.
  • OccurenceType — OccurenceType.Occurence.
  • IsValid — true.
  • PresentationOption — define it as a get/set property.

For examples of leveraging the various IOccurence members, take a look at some of the its built-in ReSharper implementors.