H-5839, FE-488: Petrinaut: LSP-like interface for Diagnostics and Code Editor

[kube]

🌟 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

Loading

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.

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

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[kube]

• FE-225, H-6116, H-6286: Update Petrinaut UI #8472 : 2 dependent PRs (#8463 , #8509 )
• H-5839, FE-488: Petrinaut: LSP-like interface for Diagnostics and Code Editor #8300 👈 (View in Graphite)
• FE-223, H-5780, H-6227: Setup Petrinaut inside HASH + Build with Vite 8 and TypeScript 7 #8369
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[cursor]

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.

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[augmentcode]

🤖 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.

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