One the server side xtext is used to provide a language server. On the client side the Theia framework is used to communicate with it. This guide is for KIELER developers who want to build functinality in form of language server extensions for KEITH and frontend developers for KEITH that want to know how to communicate with the LS.
This part of the guide covers the server side development for KEITH, the language server (LS). It is adviced to have a look at the existing implementation in the language.server plugin.
Currently the LS is an eclipse application and it has to be started as one. To do this the Manifest.mf in the META-INF folder of your language server plugin has to be changed. In the extensions tab a new extension point for org.eclipse.core.runtime.applications has to be created. This extension points maps to your start class of your language server, which has to be an IApplication that implements a start method.
This start class should somehow distinguish between connecting via socket and connecting via stdin/out.
Language that are registered here are always xtext languages.
Since we are in the semantics repository we can use java ServiceLoader to add new ILSSetups, which register a language.
interface ILSSetup { def Injector doLSSetup() } class SCTXLSSetup implements ILSSetup { override doLSSetup() { return SCTXIdeSetup.doSetup() } } |
A language that wants to be included in the LS can implement this interface. Registering SCTXLSSetup via ServiceLoader allows to register all available languages like this:
for (contribution: KielerServiceLoader.load(ILSSetupContribution)) { contribution.LSSetup.doLSSetup() } |
Have a look at one of the LSSetups defined in the semantic.
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We use java ServiceLoader to register stuff. Here is a small example how a LanguageServerExtension is registered via a ServiceLoader and how it is used:
This is a LanguageServerExtension. It has to be used in the de.cau.cs.kieler.language.server plugin. Since the language-server-plugin should not have dependencies to all plugins that define a language server extension dependency inversion is used to prevent that. A ServiceLoader via dependency inversion does exactly that.
Here is such an example extension, the KiCoolLanguageServerExtension:
package de.cau.cs.kieler.kicool.ide.language.server /** * @author really fancy name * */ @Singleton class KiCoolLanguageServerExtension implements ILanguageServerExtension, CommandExtension, ILanguageClientProvider { // fancy extension stuff KeithLanguageClient client // A language server extension must implement the initialize method, // it is however only called if the extension is registered via a language. // This should never be the case, so this is never called. override initialize(ILanguageServerAccess access) { this.languageServerAccess = access } // implement ILanguageClientProvider override setLanguageClient(LanguageClient client) { this.client = client as KeithLanguageClient } // implement ILanguageClientProvider override getLanguageClient() { return this.client } } |
The CommandExtension defines all commands (requests or notifications) that are send from client to server. An example how this looks like can be seen in the code snippet Example CommandExtension is an example how to define a server side extension interface.
The ILanguageClientProvider should be implemented by an extension that plans to send messages from the server to the client.
This language server extension is provided by a corresponding contribution, which is later used to access it:
package de.cau.cs.kieler.kicool.ide.language.server import com.google.inject.Injector import de.cau.cs.kieler.language.server.ILanguageServerContribution /** * @author really fancy name * */ class KiCoolLanguageServerContribution implements ILanguageServerContribution { override getLanguageServerExtension(Injector injector) { return injector.getInstance(KiCoolLanguageServerExtension) } } |
Create a file called de.cau.cs.kieler.language.server.ILanguageServerContribution in <plugin>/META-INF/services/ (in this example this is de.cau.cs.kieler.kicool.ide). The name of the file refers to the contribution interface that should be used to provide the contribution. The content of the file is the following:
de.cau.cs.kieler.kicool.ide.language.server.KiCoolLanguageServerContribution |
This is the fully qualified name of the contribution written earlier.
The language server uses all LanguageServerExtensions like this:
var iLanguageServerExtensions = <Object>newArrayList(languageServer) // list of all language server extensions for (lse : KielerServiceLoader.load(ILanguageServerContribution)) { // dynamically load all contributions to add LS extensions iLanguageServerExtensions.add(lse.getLanguageServerExtension(injector)) } |
The resulting list of implementions is used to add the extensions to the language server.
The interfaces used for dynamic registration are in the semantics repository. If you define a pragmatics LS extension you have to statically add these extensions to your list. |
See example above for ServiceLoader and initial stuff.
What is still missing are the contents of the CommandExtension implemented by the KiCoolLanguageServerExtension. This is an interface defining all additional commands. The CommandExtension looks like this.
package de.cau.cs.kieler.kicool.ide.language.server import java.util.concurrent.CompletableFuture import org.eclipse.lsp4j.jsonrpc.services.JsonRequest import org.eclipse.lsp4j.jsonrpc.services.JsonSegment /** * Interface to the LSP extension commands * * @author really fancy name * */ @JsonSegment('keith/kicool') interface CommandExtension { /** * Compiles file given by uri with compilationsystem given by command. */ @JsonRequest('compile') def CompletableFuture<CompilationResults> compile(String uri, String clientId, String command, boolean inplace); /** * Build diagram for snapshot with id index for file given by uri. Only works, if the file was already compiled. */ @JsonRequest('show') def CompletableFuture<String> show(String uri, String clientId, int index) /** * Returns all compilation systems which are applicable for the file at given uri. * * @param uri URI as string to get compilation systems for * @param filter boolean indicating whether compilation systems should be filtered */ @JsonRequest('get-systems') def CompletableFuture<Object> getSystems(String uri, boolean filterSystems) } |
This defines three json-rpc commands: "keith/kicool/compile", "keith/kicool/show", "keith/kicool/get-systems". These are implemented in KiCoolLanguageServerExtension.
Not only messages from client to server but rather messages from server client might be needed.
Messages that can be send from server to client are defined in the KeithLanguageClient:
/** * LanguageClient that implements additional methods necessary for server client communication in KEITH. * * @author really fancy name * */ @JsonSegment("keith") interface KeithLanguageClient extends LanguageClient { @JsonNotification("kicool/compile") def void compile(Object results, String uri, boolean finished); @JsonNotification("kicool/cancel-compilation") def void cancelCompilation(boolean success); // Not only notifications, but also server client requests should be possible, but currently there is no use case for that. } |
These messages can be caught on the client side by defining the message that is caught like this:
export const snapshotDescriptionMessageType = new NotificationType<CodeContainer, void>('keith/kicool/compile'); |
This message type is bound to a method that should be called whenever the client receives such a message.
const lClient: ILanguageClient = await this.client.languageClient lClient.onNotification(snapshotDescriptionMessageType, this.handleNewSnapshotDescriptions.bind(this)) |
The method should receive all parameters specific in the KeithLanguageClient interface on the serevr side.
Such a notification from server to client is send like this:
future.thenAccept([ // client is the KeithLanguageClient registered in a LanguageServerExtension that implements a ILanguageClientProvider // compile is the command defined in the KeithLanguageClientInterface client.compile(new CompilationResults(this.snapshotMap.get(uri)), uri, finished) ]) |
Language server extension do not have to be registered on the client side. It is just called.
You can send a request or a notification to the language server like this:
const lclient = await this.client.languageClient const snapshotsDescriptions: CodeContainer = await lclient.sendRequest("keith/kicool/compile", [uri, KeithDiagramManager.DIAGRAM_TYPE + '_sprotty', command, this.compilerWidget.compileInplace]) as CodeContainer // or via a thenable client.languageClient.then(lClient => { lClient.sendRequest("keith/kicool/compile").then((snapshotsDescriptions: CodeContainer) => { // very important stuff } // await is preferred, since it is shorter. |
In this example client is an instance of a language client. It is usually injected like this:
@inject(KeithLanguageClientContribution) public readonly client: KeithLanguageClientContribution constructor( // other injected classes that are relevant for the constructor ) { // constructor stuff } |
There are different kinds of widgets that are commonly used inĀ KEITH or in existing Theia packages.
If a widget has a state it should implement the StatefulWidget interface, which allows to imlement a store and restore method.
Look at examples in KEITH or Theia to see how this is done.
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