[POM-leading for DSLs] Routing to dedicated remote language servers by toinehartman · Pull Request #1069 · usethesource/rascal-language-servers

toinehartman · 2026-04-28T16:22:15Z

This PR is the first of a series. gradually implementing POM-leading behavior in DSLs/the parametric server.
This PR introduces a routing language server, which delegates incoming LSP requests to the appropriate parametric language server, dedicated to a single language. A dedicated server is started upon initial language registration.

Closes #1076

…ing-for-dsls-redo

toinehartman · 2026-05-11T13:47:34Z

    }

-    public SemanticTokensWithRegistrationOptions options() {
+    public static SemanticTokensWithRegistrationOptions options() {


This change allows us to make ParametricTextDocumentService::setStaticServerCapabilities static as well and re-use it in the new RoutingTextDocumentService

toinehartman · 2026-05-11T13:49:45Z


-    RascalWorkspaceService(ExecutorService exec, IBaseTextDocumentService documentService) {
-        super(exec, documentService);
+    RascalWorkspaceService(ExecutorService exec) {


This argument is replaced by a pair function

…010-pom-leading-for-dsls/remote-routing

sonarqubecloud · 2026-05-12T12:06:49Z

Quality Gate passed

Issues
11 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

toinehartman · 2026-05-12T12:25:42Z

+                    , "-cp", classPath
+                    , "org.rascalmpl.vscode.lsp.parametric.ParametricLanguageServer"
+                    , "--exitWhenEmpty"
+                    // , new GsonBuilder().create().toJson(lang, LanguageParameter.class).replace("\"", "\\\"") // escape JSON string on command line


It would be nice you use the dedicated language feature of the parametric LSP here, but then we should also probably swallow the registerLanguage call that triggered this, as otherwise, we are registering twice and wasting resources.

DavyLandman

I think this is heading in the right direction. But it's not ready yet.

DavyLandman · 2026-05-12T19:49:07Z

+    private final Map<String, String> languagesByExtension = new ConcurrentHashMap<>();
+    // NOTE
+    // 1. This map should only contains running server processes.
+    // 2. Upon removal from this map, the process should be killed to avoid resource leaks.


we should also register a shutdown hook to always close our child processes.

DavyLandman · 2026-05-12T19:52:43Z

+    }
+
+    public CompletableFuture<IBaseLanguageServerExtensions> route(String extension) {
+        return safeLanguage(extension).map(this::languageByName).orElseThrow(() -> {


this exception is thrown in the context of route not in the context of the completable future, so that might be not so nice.

Same is true for the safeLanguage exception.

DavyLandman · 2026-05-12T19:54:23Z

+    }
+
+    private static String classPath(LanguageParameter lang) {
+        var separator = System.getProperty("path.separator");


let's use File.pathSeparator instead. (this maybe negates the need for this).

DavyLandman · 2026-05-12T19:57:02Z

+        } catch (IOException e) {
+            logger.error("Error while parsing path config {}", lang.getPathConfig(), e);
+            logger.warn("Could not compute class path for {}; falling back to class path of routing server", lang.getName());
+            return System.getProperty("java.class.path");


I'm not sure if we should have a fallback like this. It can lead to all kinds of down stream errors that a user didn't suspect, all because of like some parse error in the pom.xml that wasn't reported to the user as a breaking error.

DavyLandman · 2026-05-12T19:59:40Z

+            // Check if we are in Rascal-LSP
+            var classPath = new StringBuilder();
+            if (isRascalLspProject(rootProject)) {
+                classPath.append(separator);


Maybe we should collect all entries in a list, and then at the end join them with the path sep as element seperator?

so that he final substring can also be skipped.

DavyLandman · 2026-05-13T09:02:45Z

+    @SuppressWarnings("unused")
+    private final ExecutorService exec;


why keep it around if we don't use it?

DavyLandman · 2026-05-13T09:12:39Z

+        this.parentServer = server;
+    }
+
+    private ActualRoutingLanguageServer availableServer() {


I don't understand this extra edge, why do we need to loop back to the server? I've had this same question when reading this PR, I don't like all these cycles, so can we do without?

DavyLandman · 2026-05-13T09:13:10Z

+                .thenCompose(s -> s.getWorkspaceService().executeCommand(commandParams));
+        }
+
+        return CompletableFutureUtils.completedFuture(commandParams.getCommand() + " was ignored.", getExecutor());


can we say why it was ignored?

DavyLandman · 2026-05-13T09:27:50Z

+    @JsonDelegate
+    IBaseTextDocumentService getIBaseTextDocumentService();


Why this extension? can we add a comment? I don't see how the IBaseTextDocumentService could ever be serialized over json?

DavyLandman · 2026-05-13T09:28:37Z

+    try {
+        root = resolveLocation(|project://rascal-lsp|);
+    } catch SchemeNotSupported(_): {
+        root = resolveLocation(|cwd:///../../../rascal-lsp|);


let's add a comment to explain why we're doing this.

toinehartman added 24 commits April 22, 2026 10:11

Boilerplate for LSP router.

f1e1748

Symmetric pairing of services.

d838723

Routing language server as special case of parametric.

50c8fc0

Extract routing services.

f320f88

Basic delegate server.

fe01d94

Factor out initialization.

2b6d9a4

Route all client calls back to the original client.

3134be6

Simplify routing with utility interfaces.

4ed8701

Move classes to appropriate package.

0e86a65

Allow routing by extensions.

1fe0e43

Forward textDocument/* LSP calls to delegates.

d784529

Start multiple delegate servers on predefined ports.

3a4b347

Add deployed launch config.

381b847

Fix deployed running and cleanup.

8b3fbc1

Fix lint errors and nulls.

8d5bae3

Only interrupt on interruption exception.

0f43434

Shut down child processes on exit.

40e0dc9

Implement command execution.

bd14c05

Print port number in log message.

d5d3e1b

Prepare for class path based on POM.

60a3509

Log language registration calls.

410c2cb

Merge remote-tracking branch 'origin/main' into feature/1010-pom-lead…

310ec57

…ing-for-dsls-redo

Do not resolve project location.

096ad1a

Fix nullability.

aa08777

toinehartman self-assigned this Apr 28, 2026

toinehartman added the enhancement New feature or request label Apr 28, 2026

toinehartman changed the base branch from main to feature/1010-pom-leading-for-dsls/final April 28, 2026 16:23

toinehartman added 3 commits April 28, 2026 18:36

Rename caller interface name & methods.

12742a4

Rename router interface.

c9991f3

Fix dedicated language arg.

34f3daa

toinehartman force-pushed the feature/1010-pom-leading-for-dsls/remote-routing branch from 7bf6060 to 017ab39 Compare May 5, 2026 09:30

toinehartman added 4 commits May 5, 2026 16:49

Properly compose and await language registration.

67950a3

Re-do cleanup of child processes without hooks or bookkeeping.

3feac15

Make class path separator OS-dependent.

9054f9b

Fix CF by casting function.

6ee7eca

toinehartman force-pushed the feature/1010-pom-leading-for-dsls/remote-routing branch from 683fef2 to 6ee7eca Compare May 5, 2026 15:55

toinehartman added 4 commits May 8, 2026 12:21

Encode as base64 when decoding is needed.

1fd3c42

Add TODO for later.

03e6011

Route commands via workspace service like other servers.

b51e497

Move routing server to dedicated package.

3acc0ce

toinehartman force-pushed the feature/1010-pom-leading-for-dsls/remote-routing branch from 8e1ed67 to b434ff4 Compare May 11, 2026 12:43

toinehartman added 2 commits May 11, 2026 15:22

Proxy IValues by wrapping the wrap JSON.

e648018

Skip some tests that we implement later.

f026e3c

toinehartman commented May 11, 2026

View reviewed changes

toinehartman added 4 commits May 11, 2026 16:12

Rename LanguageServerRouter => ActualRoutingLanguageServer

37a0ebe

Various small fixes and reverts.

97905d9

Merge branch 'feature/1010-pom-leading-for-dsls/final' into feature/1…

e70e5e0

…010-pom-leading-for-dsls/remote-routing

Used proxied language client in routing server.

6f475fe

toinehartman force-pushed the feature/1010-pom-leading-for-dsls/remote-routing branch from b434ff4 to 6f475fe Compare May 11, 2026 14:57

toinehartman added 2 commits May 11, 2026 17:42

Improved JSON number parser fallbacks.

842de26

Remove/change some TODOs.

ea42bd3

toinehartman force-pushed the feature/1010-pom-leading-for-dsls/remote-routing branch from 600df56 to 3ed29d4 Compare May 12, 2026 11:51

Inline future caller utils.

2b01979

toinehartman force-pushed the feature/1010-pom-leading-for-dsls/remote-routing branch from 3ed29d4 to 2b01979 Compare May 12, 2026 11:59

toinehartman marked this pull request as ready for review May 12, 2026 12:22

toinehartman linked an issue May 12, 2026 that may be closed by this pull request

Parametric routing layer with dedicated servers #1076

Open

toinehartman commented May 12, 2026

View reviewed changes

DavyLandman requested changes May 13, 2026

View reviewed changes

		@SuppressWarnings("unused")
		private final ExecutorService exec;

		@JsonDelegate
		IBaseTextDocumentService getIBaseTextDocumentService();

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sonarqubecloud Bot commented May 12, 2026

Quality Gate passed

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toinehartman commented Apr 28, 2026 •

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