Decrease input-lag for large queries (#158)

* proof of concept

* merge main

* works again

* fix overuse of main channel

* mellan

* tests work

* fix worker thread for node as well

* self review

* self review

* self review

* fix build

* tests

* fix e2e test

* merge semantic analsysis and syntax errors again

* review comments

* self review

* fix tests

* worker pool-ish for vscode

* smarter 'pool' mgmt

* kindaworks

* works

* cleanup new parser adapter

* restore pkg json

* workerpool

* worker pool for client as well

* cleanup workers

* fix errors

* fix tests

* fix todos

* fix build

* test-are-green

* works for vite

* fixlint

* self review

* re-add proper build

* fix input lag even when parse is fast

* add changeset

* fix e2e test

* pr comments

.changeset/pink-chefs-trade.md

@@ -0,0 +1,9 @@
+---
+'@neo4j-cypher/react-codemirror-playground': patch
+'@neo4j-cypher/language-support': patch
+'@neo4j-cypher/react-codemirror': patch
+'neo4j-cypher-vscode-extension': patch
+'@neo4j-cypher/language-server': patch
+---
+
+Moves semantic analysis to a separate worker file

packages/language-server/package.json

@@ -35,9 +35,11 @@
   },
   "dependencies": {
     "@neo4j-cypher/language-support": "2.0.0-next.2",
+    "lodash.debounce": "^4.0.8",
     "neo4j-driver": "^5.3.0",
     "vscode-languageserver": "^8.1.0",
-    "vscode-languageserver-textdocument": "^1.0.8"
+    "vscode-languageserver-textdocument": "^1.0.8",
+    "workerpool": "^9.0.4"
   },
   "scripts": {
     "build": "tsc -b && npm run bundle && npm run make-executable",
@@ -47,6 +49,7 @@
     "watch": "tsc -b -w"
   },
   "devDependencies": {
+    "@types/lodash.debounce": "^4.0.9",
     "esbuild": "^0.19.4"
   }
 }

packages/language-server/src/lint-worker.ts

@@ -0,0 +1,14 @@
+import { validateSemantics } from '@neo4j-cypher/language-support';
+import workerpool from 'workerpool';
+
+workerpool.worker({ validateSemantics });
+
+type LinterArgs = Parameters<typeof validateSemantics>;
+
+export type LinterTask = workerpool.Promise<
+  ReturnType<typeof validateSemantics>
+>;
+
+export type LintWorker = {
+  validateSemantics: (...args: LinterArgs) => LinterTask;
+};

packages/language-server/src/linting.ts

@@ -0,0 +1,63 @@
+import {
+  findEndPosition,
+  parserWrapper,
+  validateSyntax,
+} from '@neo4j-cypher/language-support';
+import debounce from 'lodash.debounce';
+import { join } from 'path';
+import { Diagnostic, TextDocumentChangeEvent } from 'vscode-languageserver';
+import { TextDocument } from 'vscode-languageserver-textdocument';
+import workerpool from 'workerpool';
+import { LinterTask, LintWorker } from './lint-worker';
+
+const pool = workerpool.pool(join(__dirname, 'lint-worker.js'), {
+  minWorkers: 2,
+  workerTerminateTimeout: 2000,
+});
+
+let lastSemanticJob: LinterTask | undefined;
+
+async function rawLintDocument(
+  change: TextDocumentChangeEvent<TextDocument>,
+  sendDiagnostics: (diagnostics: Diagnostic[]) => void,
+) {
+  const { document } = change;
+
+  const query = document.getText();
+  if (query.length === 0) {
+    return;
+  }
+
+  const syntaxErrors = validateSyntax(query, {});
+
+  sendDiagnostics(syntaxErrors);
+
+  if (syntaxErrors.length === 0) {
+    try {
+      if (lastSemanticJob !== undefined && !lastSemanticJob.resolved) {
+        void lastSemanticJob.cancel();
+      }
+
+      const proxyWorker = (await pool.proxy()) as unknown as LintWorker;
+      lastSemanticJob = proxyWorker.validateSemantics(query);
+      const result = await lastSemanticJob;
+
+      sendDiagnostics(
+        result.map((el) => findEndPosition(el, parserWrapper.parsingResult)),
+      );
+    } catch (err) {
+      if (!(err instanceof workerpool.Promise.CancellationError)) {
+        console.error(err);
+      }
+    }
+  }
+}
+
+export const lintDocument = debounce(rawLintDocument, 600, {
+  leading: false,
+  trailing: true,
+});
+
+export const cleanupWorkers = () => {
+  void pool.terminate();
+};

packages/language-server/src/server.ts

@@ -1,5 +1,6 @@
 import {
   createConnection,
+  Diagnostic,
   DidChangeConfigurationNotification,
   InitializeResult,
   ProposedFeatures,
@@ -11,10 +12,7 @@ import {
 
 import { TextDocument } from 'vscode-languageserver-textdocument';
 
-import {
-  syntaxColouringLegend,
-  validateSyntax,
-} from '@neo4j-cypher/language-support';
+import { syntaxColouringLegend } from '@neo4j-cypher/language-support';
 import { Neo4jSchemaPoller } from '@neo4j-cypher/schema-poller';
 import { doAutoCompletion } from './autocompletion';
 import { doSignatureHelp } from './signatureHelp';
@@ -23,6 +21,8 @@ import { Neo4jSettings } from './types';
 
 const connection = createConnection(ProposedFeatures.all);
 
+import { cleanupWorkers, lintDocument } from './linting';
+
 // Create a simple text document manager.
 const documents: TextDocuments<TextDocument> = new TextDocuments(TextDocument);
 
@@ -73,18 +73,14 @@ connection.onInitialized(() => {
   );
 });
 
-// Trigger the syntactic errors highlighting on every document change
-documents.onDidChangeContent((change) => {
-  const document = change.document;
-  const diagnostics = validateSyntax(
-    document.getText(),
-    neo4jSdk.metadata?.dbSchema ?? {},
-  );
-  void connection.sendDiagnostics({
-    uri: document.uri,
-    diagnostics: diagnostics,
-  });
-});
+documents.onDidChangeContent((change) =>
+  lintDocument(change, (diagnostics: Diagnostic[]) => {
+    void connection.sendDiagnostics({
+      uri: change.document.uri,
+      diagnostics,
+    });
+  }),
+);
 
 // Trigger the syntax colouring
 connection.languages.semanticTokens.on(
@@ -121,4 +117,9 @@ connection.onDidChangeConfiguration(
 );
 
 documents.listen(connection);
+
 connection.listen();
+
+connection.onExit(() => {
+  cleanupWorkers();
+});