H-5839, FE-488: Petrinaut: LSP-like interface for Diagnostics and Code Editor by kube · Pull Request #8300 · hashintel/hash

kube · 2026-01-23T17:28:47Z

🌟 What is the purpose of this PR?

Add a TypeScript Language Service layer for Petrinaut's Monaco editors, providing real-time diagnostics, completions, hover info, and signature help — all running off the main thread in a WebWorker, communicating via an LSP-inspired JSON-RPC 2.0 protocol with standard vscode-languageserver-types.

graph TD
  subgraph Main Thread
    SDCPN["SDCPNContext"] --updates--> LC["LanguageClientContext"]
    LC --> Sync["Sync Components"]
    Monaco["MonacoContext"] --> Sync
    CodeEditor --uses--> Monaco
  end

  subgraph WebWorker
    Worker["language-server.worker"] --> LS["SDCPNLanguageServer"]
  end

  LC -- "notifications" --> Worker
  Worker -. "diagnostics" .-> LC
  Sync -- "requests" --> Worker
  Worker -. "responses" .-> Sync

Protocol messages (JSON-RPC 2.0)

Direction	Method	Payload
Main → Worker	`initialize`, `sdcpn/didChange`, `textDocument/didChange`	SDCPN model / document text
Worker → Main	`textDocument/publishDiagnostics`	`Diagnostic[]` per URI
Main → Worker	`textDocument/completion`	`Position` → `CompletionList`
Main → Worker	`textDocument/hover`	`Position` → `Hover`
Main → Worker	`textDocument/signatureHelp`	`Position` → `SignatureHelp`

Note: While the SDCPNLanguageServer is instantiated once and reused, every change — whether to the net structure, types, or code — currently sends the full SDCPN to the WebWorker via sdcpn/didChange. This will need to be made more granular in the future (e.g. per-item deltas).

🔗 Related links

H-5839 (internal)

🔍 What does this change?

Architecture

Extract Monaco setup into a dedicated async-loaded module (monaco/provider.tsx) with a module-level lazy singleton to prevent re-initialization
Consolidate the LSP layer into a self-contained module (lsp/)
Move the TypeScript language server to a WebWorker (lsp/worker/language-server.worker.ts) with a JSON-RPC 2.0 protocol
Bundle TypeScript lib files into the worker (no CDN dependency)

LSP-inspired protocol (lsp/worker/protocol.ts)

All data types use official LSP types from vscode-languageserver-types (Diagnostic, CompletionItem, CompletionList, Hover, SignatureHelp, Position, Range)
Notifications: initialize, sdcpn/didChange, textDocument/didChange
Requests: textDocument/completion, textDocument/hover, textDocument/signatureHelp
Server push: textDocument/publishDiagnostics (per-URI diagnostic notifications)
Position model uses LSP Position { line, character } with offset↔position conversion utilities bridging the TS LanguageService

Persistent LanguageService (lsp/lib/create-sdcpn-language-service.ts)

SDCPNLanguageServer class creates ts.createLanguageService() once and reuses it across SDCPN changes
syncFiles(sdcpn) diffs virtual files incrementally (add/remove/update) rather than recreating everything
updateDocumentContent() for single-file typing updates
getFileContent() for offset↔position conversion

Shared modules

lsp/lib/document-uris.ts: Single source of truth for URI ↔ file path ↔ item type mapping, consumed by both the worker and Monaco components
lsp/lib/ts-to-lsp.ts: Pure TS → LSP type conversion functions (toLspSeverity, toCompletionItemKind, serializeDiagnostic), extracted from the worker for testability
lsp/lib/position-utils.ts: Offset ↔ LSP Position conversion utilities

Language features (Monaco sync components)

Diagnostics: DiagnosticsSync maps LSP Diagnostic ranges to Monaco markers (diagnostics-sync.tsx)
Completions: CompletionSync with LSP CompletionItemKind → Monaco kind mapping (completion-sync.tsx)
Hover: HoverSync rendering LSP MarkupContent (hover-sync.tsx)
Signature help: SignatureHelpSync with LSP SignatureHelp → Monaco mapping (signature-help-sync.tsx)
All sync components convert between Monaco 1-based and LSP 0-based positions at the boundary

Cleanup

Remove @dnd-kit dependency and feature flags
Remove rollup-plugin-visualizer dependency

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

modifies an npm-publishable library and I have added a changeset file(s)

📜 Does this require a change to the docs?

The changes in this PR:

are internal and do not require a docs change

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

do not affect the execution graph

🛡 What tests cover this?

checker.test.ts: 20 tests covering SDCPN validation with the SDCPNLanguageServer
create-sdcpn-language-service.test.ts: 11 tests covering dot completions, top-level completions, updateDocumentContent mutability, syncFiles structural updates, and differential equation completions
position-utils.test.ts: 12 tests covering offsetToPosition, positionToOffset, and roundtrip identity
document-uris.test.ts: 22 tests covering URI construction, parsing, file path conversion, and roundtrip identity for all item types
ts-to-lsp.test.ts: 38 tests covering TS diagnostic severity → LSP severity mapping, all TS ScriptElementKind → LSP CompletionItemKind mappings, and full serializeDiagnostic conversion (multi-line ranges, chained messages, defaults)

🐾 Next steps

Adopt a real LSP library: progressively migrate to an established LSP client/server library (e.g. vscode-languageserver / vscode-languageclient) to replace custom JSON-RPC mapping and reduce protocol boilerplate.
Visualizer code support: re-add completions and diagnostics for Place visualizer editors — this is separate from the SDCPN verification/checker scope and was intentionally left out of this initial implementation.

vercel · 2026-01-23T17:28:53Z

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Project	Deployment	Actions	Updated (UTC)
hash	Error		Feb 26, 2026 11:31pm
petrinaut	Ready	Preview	Feb 26, 2026 11:31pm

2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
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kube · 2026-01-23T17:29:13Z

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libs/@hashintel/petrinaut/src/lsp/lsp.worker.ts

…o editors Wire TypeScript LanguageService features through the checker WebWorker to Monaco editors via JSON-RPC. The LanguageServiceHost is now mutable (per-file version tracking) so completions reflect current editor state. - Completions: registerCompletionItemProvider with ScriptElementKind mapping - Hover: registerHoverProvider backed by getQuickInfoAtPosition - Signature help: registerSignatureHelpProvider backed by getSignatureHelpItems - All three adjust offsets to account for injected declaration prefixes - Add tests for completions and updateFileContent in the language service Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…DCPN changes Convert the checker communication layer from ad-hoc method names and types to an LSP-inspired protocol (initialize, sdcpn/didChange, textDocument/didChange, textDocument/completion, textDocument/hover, textDocument/signatureHelp), with push-based diagnostics via textDocument/publishDiagnostics notifications. Replace the factory function with a persistent SDCPNLanguageServer class that creates ts.createLanguageService() once and incrementally syncs virtual files (add/remove/update) when the SDCPN structure changes, instead of recreating from scratch on every mutation. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…ypes Replace hand-rolled Diagnostic, CompletionItem, Hover, and SignatureHelp types with official LSP types from vscode-languageserver-types. Protocol now uses LSP Position (line/character) instead of raw offsets, with offset<->position conversion utilities bridging the TS LanguageService (offset-based) and LSP (Position-based) worlds. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Use React 19 Context shorthand, derive totalDiagnosticsCount directly instead of useMemo, and extract pure helper functions for building the diagnostics map. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Fix import sorting, remove unused imports, simplify unnecessary type assertions and conditions, avoid array index keys, and fix no-return-assign in provider singleton. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

….worker Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…ntent The worker was converting Monaco positions against the full file content (prefix + user code), but Monaco positions are relative to the visible user code only. This caused double-counting of the prefix offset since SDCPNLanguageServer methods already add prefixLength internally. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Add key={petriNetId} so the language client remounts with fresh state when switching between Petri nets. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Monaco providers now call notifyDocumentChanged before each completion/hover/signatureHelp request so the worker always has up-to-date content when converting positions. Without this, typing a trigger character (e.g. ".") could race the SDCPN state sync, causing the worker to compute offsets against stale text. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cursor · 2026-02-26T22:56:46Z

PR Summary

Medium Risk
Moderate risk because it replaces Petrinaut’s in-browser TypeScript tooling and diagnostics flow with a new WebWorker + JSON-RPC layer and updates build/CSP settings that could affect editor/runtime behavior in production.

Overview
Introduces a new LSP-inspired language service layer for Petrinaut’s Monaco editors, running TypeScript analysis in a WebWorker and exposing diagnostics, completions, hover, and signature help via a small JSON-RPC protocol (lsp/worker/*).

Replaces the previous on-main-thread checker/Monaco typings setup with LanguageClientProvider + MonacoProvider and Monaco sync components that push diagnostics into Monaco markers and forward completion/hover/signature requests to the worker; editor model URIs are centralized via document-uris helpers.

Cleans up and adjusts packaging/security: removes CDN-related CSP allowances, drops the frontend webpack browser fallbacks previously used for typescript, adds vscode-languageserver-types, and tweaks Petrinaut’s Vite worker build replacements to avoid Node/process detection issues in the worker. Also removes arc reordering/feature-flag DnD UI, simplifying arc list items.

^{Written by Cursor Bugbot for commit d86a788. This will update automatically on new commits. Configure here.}

apps/hash-frontend/src/lib/csp.ts

libs/@hashintel/petrinaut/src/lsp/provider.tsx

libs/@hashintel/petrinaut/src/views/Editor/panels/PropertiesPanel/place-properties.tsx

augmentcode · 2026-02-26T23:01:24Z

🤖 Augment PR Summary

Summary: This PR introduces an LSP-inspired TypeScript Language Service layer for Petrinaut’s Monaco editors, moving diagnostics and IntelliSense work off the main thread into a WebWorker.

Changes:

Adds a JSON-RPC 2.0 protocol (based on vscode-languageserver-types) between main thread and worker.
Implements a persistent SDCPNLanguageServer with an incrementally updated virtual FS/LanguageServiceHost.
Creates Monaco “sync” components for diagnostics, completion, hover, and signature help backed by the worker.
Centralizes URI↔file-path mapping and TS→LSP conversions with dedicated tests.
Refactors Petrinaut to use LanguageClientProvider + MonacoProvider and removes the old in-main-thread checker/Monaco typings hook.
Updates CSP/Next/Vite configuration to support local Monaco + worker-based TypeScript without CDN dependencies.

Technical Notes: Monaco’s built-in TypeScript worker features are disabled and replaced by worker-backed providers; diagnostics are pushed from the worker and mirrored into Monaco markers.

_{🤖 Was this summary useful? React with 👍 or 👎}

augmentcode

Review completed. 3 suggestions posted.

Comment augment review to trigger a new review at any time.

augmentcode · 2026-02-26T23:01:25Z

libs/@hashintel/petrinaut/src/lsp/provider.tsx

+    } else {
+      client.notifySDCPNChanged(petriNetDefinition);
+    }
+  }, [petriNetDefinition, client]);


useLanguageClient() returns a fresh object each render, so including client in these effect deps can retrigger initialize/notifySDCPNChanged even when petriNetDefinition didn’t change (e.g., after diagnostics state updates). Consider stabilizing client (memoizing the returned API) or depending on specific stable callbacks instead.

Severity: medium

Other Locations

libs/@hashintel/petrinaut/src/lsp/provider.tsx:54

_{🤖 Was this useful? React with 👍 or 👎, or 🚀 if it prevented an incident/outage.}

Same as above — React Compiler handles this automatically.

augmentcode · 2026-02-26T23:01:25Z

libs/@hashintel/petrinaut/src/views/Editor/panels/PropertiesPanel/place-properties.tsx

-              />
-            </div>
+            <CodeEditor
+              path={`inmemory://sdcpn/places/${place.id}/visualizer.tsx`}


This editor uses an inmemory://sdcpn/places/... URI, but the worker URI mapping currently only recognizes transitions + differential equations; with Monaco’s built-in TS features disabled, this model will likely have no completions/hover/diagnostics. Is the visualizer intentionally excluded, or should it be added to the URI mapping/worker support?

Severity: medium

_{🤖 Was this useful? React with 👍 or 👎, or 🚀 if it prevented an incident/outage.}

Intentional — see above.

augmentcode · 2026-02-26T23:01:25Z

libs/@hashintel/petrinaut/src/lsp/lib/position-utils.ts

+    i++;
+  }
+
+  return i + position.character;


positionToOffset can return an offset beyond text.length when position.line/position.character is out of range, which could propagate into TS LanguageService queries. Consider clamping to the text length (similar to offsetToPosition’s clamping) for defensive safety.

Severity: low

_{🤖 Was this useful? React with 👍 or 👎, or 🚀 if it prevented an incident/outage.}

Valid — adding a clamp for symmetry with offsetToPosition.

…offsetToPosition` Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cursor

Cursor Bugbot has reviewed your changes and found 2 potential issues.

^{Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

libs/@hashintel/petrinaut/src/lsp/lib/position-utils.ts

libs/@hashintel/petrinaut/src/lsp/worker/use-language-client.ts

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FE-223, H-5780, H-6227: Setup Petrinaut inside HASH + Build with Vite 8 and TypeScript 7 #8369

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kube changed the title ~~H-5839: Add LSP layer for Petrinaut Monaco editors~~ H-5839, FE-488: Add LSP layer for Petrinaut Monaco editors Feb 19, 2026

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kube and others added 13 commits February 26, 2026 23:25

H-5839: Add changeset for LSP language service layer

f98b7d2

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

H-5839: Modernize LanguageClientProvider to React 19 patterns

b1ef02a

Use React 19 Context shorthand, derive totalDiagnosticsCount directly instead of useMemo, and extract pure helper functions for building the diagnostics map. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

H-5839: Consolidate document URI mapping into single shared module

edf90bf

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

H-5839: Extract TS-to-LSP conversion functions into testable module

441087f

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

H-5839: Rename checker/ to lsp/ and checker.worker to language-server…

e6188e6

….worker Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

H-5839: Reset LanguageClientProvider when petriNetId changes

088e22b

Add key={petriNetId} so the language client remounts with fresh state when switching between Petri nets. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Lint

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H-5839: Clamp positionToOffset to text.length for symmetry with `…

d86a788

…offsetToPosition` Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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🌟 What is the purpose of this PR?

🔗 Related links

🔍 What does this change?

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

📜 Does this require a change to the docs?

🕸️ Does this require a change to the Turbo Graph?

🛡 What tests cover this?

🐾 Next steps

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