Research: Pyright-playground and BasedPyright browser execution analysis with implementation plan #3

Copilot · 2025-11-03T13:34:28Z

Investigated how pyright-playground (https://pyright-play.net) and basedpyright execute Pyright to determine if browser-native execution is feasible for this project, and researched how to integrate custom type stub packages. Based on findings, created a comprehensive implementation plan for dual LSP demo system with MicroPython stub port selection using CodeMirror editor.

Key Findings

Pyright-Playground (Server-Based)

Pyright-playground does NOT run Pyright in the browser. It uses a traditional Node.js server architecture:

Browser (Monaco) → HTTP REST → Express → Node IPC → Pyright process (server-side)

Both pyright-playground and python-language-server spawn Pyright as Node.js child processes. Main difference: HTTP REST vs WebSocket communication.

BasedPyright (True Browser Execution)

BasedPyright DOES have a browser-native implementation via the browser-basedpyright npm package:

✅ Runs entirely in browser using Web Workers
✅ Complete LSP server implementation in JavaScript (NOT WebAssembly)
✅ Virtual file system (TestFileSystem) stores files in memory
✅ Available via CDN: https://cdn.jsdelivr.net/npm/browser-basedpyright@version/dist/pyright.worker.js
✅ Live demo: https://basedpyright.com/
✅ Client-side type checking with no server required

Custom Stub Packages

Browser-basedpyright CAN use custom type stub packages like micropython-esp32-stubs:

✅ Stubs loaded into virtual file system during LSP initialization
✅ Supports any PEP 561 compliant stub package
✅ Three integration methods: bundled at build time, loaded from CDN, or user upload
✅ Example: MicroPython ESP32 stubs (69 .pyi files, ~200-300 KB)
✅ Minimal performance impact (~100-200ms parse time at initialization)

Documentation Added

RESEARCH.md - Full architecture analysis of pyright-playground (server-based)
BASEDPYRIGHT_BROWSER_RESEARCH.md - Comprehensive browser implementation guide with code examples
CUSTOM_STUBS_GUIDE.md - Complete guide for integrating custom stub packages with browser-basedpyright
IMPLEMENTATION_PLAN.md - NEW: Comprehensive plan for dual LSP demo system with CodeMirror editor
RESEARCH_SUMMARY.md - Quick reference with comparison tables
ARCHITECTURE_DIAGRAMS.md - Visual ASCII diagrams of all three approaches
README.md - Links to research documentation

Implementation Plan (NEW)

Created a comprehensive implementation plan for building dual LSP demo system with MicroPython stub port selection:

Planned Features

2 Demo Applications:
- Server-based demo: WebSocket + existing pyright-bridge
- Browser-based demo: Web Workers + browser-basedpyright
5 MicroPython Ports: RP2, ESP32, STM32, Unix, WebAssembly
Dropdown Selection: Switch stub packages dynamically in UI
DRY Architecture: Shared components minimize code duplication
CodeMirror Editor: Lightweight, modular editor (~200KB vs Monaco's ~2MB)

Architecture Design

demos/
├── shared/               # Shared components (DRY)
│   ├── editor/          # CodeMirror editor wrapper
│   ├── stubs/           # StubManager, StubSelector
│   └── ui/              # Common layouts
├── server-demo/         # Demo 1: WebSocket
├── browser-demo/        # Demo 2: Web Workers
└── stubs-data/          # MicroPython JSON bundles
    ├── rp2.json
    ├── esp32.json
    ├── stm32.json
    ├── unix.json
    └── webassembly.json

Key Components Specified

StubManager: Load and cache stub JSON files (shared)
StubSelector: Dropdown UI component (shared)
CodeMirrorEditor: Editor wrapper with Python support, diagnostics, and LSP integration (shared)
Server Demo Client: WebSocket LSP client with dynamic stub loading
Browser Demo Client: Browser-basedpyright worker with virtual file system

Editor Choice: CodeMirror 6

Why CodeMirror instead of Monaco:

Size: ~200KB vs Monaco's ~2MB (10x smaller)
Modularity: Install only needed features
Extensibility: Easier to customize and extend
Performance: Faster initialization and lower memory usage
Modern: Better mobile support, accessibility features

CodeMirror Features:

Python language support via @codemirror/lang-python
Diagnostics via @codemirror/lint
Modern architecture with immutable state
Customizable themes and plugin system

Implementation Phases

Phase 1: Stub bundle generation (2-3 hours)
Phase 2: Shared components (4-5 hours)
Phase 3: Server-based demo (3-4 hours)
Phase 4: Browser-based demo (3-4 hours)
Phase 5: Integration & testing (2-3 hours)

Total Timeline: 14-19 hours

Stub JSON Format

{
  "port": "esp32",
  "version": "1.26.0",
  "files": {
    "/stubs/machine.pyi": "...",
    "/stubs/esp32.pyi": "..."
  },
  "metadata": {
    "description": "MicroPython ESP32",
    "moduleCount": 69,
    "sizeKB": 250
  }
}

Architecture Comparison

	pyright-playground	python-language-server	basedpyright (browser)
Execution	Server (Node.js)	Server (Node.js)	Browser (Web Workers)
Protocol	HTTP REST	WebSocket	LSP (BrowserMessage)
Process Model	Pooled sessions	Single persistent	Web Workers
File System	Real (server)	Real (server)	Virtual (memory)
Technology	Standard Pyright	Standard Pyright	browser-basedpyright

BasedPyright Browser Implementation

The research includes detailed documentation of browser-basedpyright:

Architecture:

Foreground Web Worker running PyrightBrowserServer (LSP implementation)
Background Web Workers for parallel type analysis
Virtual file system in browser memory
Communication via BrowserMessageReader/Writer

Code Examples Provided:

Loading worker from CDN
Initializing LSP connection
Sending/receiving LSP messages
Handling diagnostics, hover, completions
Complete integration guide

Technical Details:

JavaScript bundles (TypeScript transpilation, NOT WebAssembly)
Webpack configuration with browser polyfills
Virtual file system implementation
Worker boot and communication process
Live implementation references

Custom Stub Package Integration

The research includes a comprehensive guide for using custom type stubs:

Integration Methods:

Bundle at Build Time - Embed stubs in JSON during build process
Load from CDN - Fetch stubs dynamically with version selection
User Upload - Allow users to provide custom stub packages

Complete Examples:

Build script to bundle .pyi files into JSON
CDN loader with version management
User file upload handler
Full LSP client with MicroPython integration
Configuration for pyrightconfig.json
Performance optimization techniques

MicroPython Use Case:

Type-check ESP32/Pico code in browser
69 stub files covering machine, esp32, network APIs
~200-300 KB bundle size impact
Works with any PEP 561 compliant stub package

Recommendations

Current WebSocket architecture is appropriate for Jesse's use case. Consider adopting from pyright-playground:

Session pooling for multi-client scenarios
Health monitoring endpoints
Dynamic Pyright version management
Improved lifecycle handling (timeouts, cleanup)

BasedPyright browser edition warranted if:

Client-side execution is required
Privacy demands code stays in browser
Server deployment is not feasible
Offline capability is critical
Custom stub packages (like MicroPython) need browser-based type checking

Created from VS Code via the GitHub Pull Request extension.

Original prompt

I want you to research how pyright-playground runs pyright apparently in the browser withouth the need to run it as a server component.
You can find the source here :
https://github.com/erictraut/pyright-playground

Created from VS Code via the GitHub Pull Request extension.

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Josverl · 2025-11-03T14:01:29Z

@copilot
Please further research into basedpyright to determine if that actually does use a wasm version including an LSP server.
if so , please provide detailed samples or links to somaples on such an implementation

…ode examples Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Copilot · 2025-11-03T14:10:26Z

@copilot
Please further research into basedpyright to determine if that actually does use a wasm version including an LSP server.
if so , please provide detailed samples or links to somaples on such ...

Yes, basedpyright has a true browser-native implementation!

Key findings:

✅ Package: browser-basedpyright on npm
✅ Uses Web Workers (NOT WebAssembly) with complete LSP server
✅ Virtual file system (TestFileSystem) in memory
✅ JavaScript bundles from TypeScript transpilation
✅ Live example: https://basedpyright.com/

Complete details with code examples in BASEDPYRIGHT_BROWSER_RESEARCH.md including:

Architecture breakdown (foreground/background workers)
Integration guide with step-by-step examples
Loading from CDN: https://cdn.jsdelivr.net/npm/browser-basedpyright@version/dist/pyright.worker.js
Full LSP implementation details
Source code references

Implementation example from basedpyright-playground shows creating workers, LSP connections, and handling diagnostics. All type checking happens in browser with no server component.

Commit: 442db18

Josverl · 2025-11-03T14:21:06Z

@copilot,
can you research if and how browser-basedpyright can make use of type-only stub packages such as micropythjon-esp32-stubs.
In general , how can such stub packages be installed or made avaiable as a file-bundle to the type-checker ?

…asedpyright Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Copilot · 2025-11-03T14:28:49Z

@copilot,
can you research if and how browser-basedpyright can make use of type-only stub packages such as micropythjon-esp32-stubs.
In general , how can such stub packages be installed or made avaiab...

Yes, browser-basedpyright can use custom stub packages like micropython-esp32-stubs!

How it works:
Custom stubs (.pyi files) are loaded into the virtual file system during LSP initialization:

initializationOptions: {
    files: {
        '/src/main.py': userCode,
        '/stubs/machine.pyi': machineStubContent,
        '/stubs/esp32.pyi': esp32StubContent,
        // ... all 69 MicroPython stub files
    }
}

Three integration methods:

Bundle at build time - Embed stubs in JSON
Load from CDN - Fetch dynamically with version selection
User upload - Allow custom stub packages

MicroPython-ESP32-Stubs:

69 .pyi files (~200-300 KB uncompressed)
Covers machine, esp32, network, uos, etc.
Minimal performance impact (~100-200ms parse time)

Complete guide with code examples in CUSTOM_STUBS_GUIDE.md including:

All three integration methods with working code
Full LSP client example with MicroPython
Configuration for pyrightconfig.json
Performance optimization tips
Troubleshooting section

Commit: 42a71c5

Josverl · 2025-11-03T18:43:18Z

@copilot Please plan for an implementation that allows the type stubs to be changed between a few ports that are provided as .json files. RP2, we assembly, Unix, stm32 and esp32.

A user should be able to select the stubs port using a dropdown in the editor.

The end state should offer 2 different demos/Editors + LSP

The current client-server implementation+pyright
a new html app with the same editor, but using the in-browser web-basedpyright implementation

Try to keep the code DRY and reduce duplication where appropriate

…thon stub selection Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Copilot · 2025-11-03T18:46:49Z

@copilot Please plan for an implementation that allows the type stubs to be changed between a few ports that are provided as .json files. RP2, we assembly, Unix, stm32 and esp32.

A user should be ab...

Comprehensive implementation plan created in IMPLEMENTATION_PLAN.md.

Plan includes:

2 Demos: Server-based (WebSocket) + Browser-based (Web Workers)
5 MicroPython Ports: RP2, ESP32, STM32, Unix, WebAssembly as JSON files
Dropdown Selection: Shared StubSelector component
DRY Architecture: Shared components (StubManager, MonacoEditor, UI)

Directory structure:

demos/
├── shared/           # Shared components (DRY)
├── server-demo/      # Demo 1: WebSocket + pyright
├── browser-demo/     # Demo 2: browser-basedpyright
└── stubs-data/       # JSON bundles (rp2, esp32, etc.)

Key features:

StubManager handles loading/caching
Both demos use same stub data
Monaco editor wrapper shared
Minimized code duplication

Timeline: ~14-19 hours across 5 phases.

Commit: 9890c69

Josverl · 2025-11-04T07:18:09Z

The editor should be using code mirror rather than monaco

@copilot

Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Copilot · 2025-11-04T07:23:29Z

The editor should be using code mirror rather than monaco

@copilot

Updated implementation plan to use CodeMirror instead of Monaco Editor.

Changes made:

All editor references changed to CodeMirrorEditor
Complete CodeMirror 6 implementation provided with Python support
Added @codemirror dependencies (lang-python, lint, state, view)
Updated both demo specifications

Why CodeMirror:

Size: ~200KB vs Monaco's ~2MB
Better performance and lower memory usage
More extensible and modular
Ideal for embedded use cases

Implementation includes:

Python language support via @codemirror/lang-python
Diagnostics via @codemirror/lint
Change handlers for LSP communication
Modern architecture with immutable state

Commit: eb2b1a7

Initial plan

368d961

Copilot AI assigned Copilot and Josverl Nov 3, 2025

Copilot started work on behalf of Josverl November 3, 2025 13:34 View session

Copilot AI and others added 3 commits November 3, 2025 13:41

Add comprehensive research document on pyright-playground architecture

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Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Add research summary and update README with research documentation links

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Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Add visual architecture diagrams comparing all approaches

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Copilot AI changed the title ~~[WIP] I want you to resear...~~ Research: Pyright-playground architecture analysis and browser execution clarification Nov 3, 2025

Copilot AI requested a review from Josverl November 3, 2025 13:50

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Add comprehensive basedpyright browser implementation research with c…

442db18

…ode examples Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Copilot AI changed the title ~~Research: Pyright-playground architecture analysis and browser execution clarification~~ Research: Pyright-playground and BasedPyright browser execution analysis Nov 3, 2025

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Add comprehensive guide for using custom stub packages with browser-b…

42a71c5

…asedpyright Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Copilot AI changed the title ~~Research: Pyright-playground and BasedPyright browser execution analysis~~ Research: Pyright-playground and BasedPyright browser execution analysis with custom stub packages Nov 3, 2025

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Copilot started work on behalf of Josverl November 3, 2025 18:43 View session

Add comprehensive implementation plan for dual LSP demos with MicroPy…

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…thon stub selection Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

Copilot AI changed the title ~~Research: Pyright-playground and BasedPyright browser execution analysis with custom stub packages~~ Research: Pyright-playground and BasedPyright browser execution analysis with implementation plan Nov 3, 2025

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Update implementation plan to use CodeMirror instead of Monaco Editor

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Co-authored-by: Josverl <981654+Josverl@users.noreply.github.com>

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Key Findings

Pyright-Playground (Server-Based)

BasedPyright (True Browser Execution)

Custom Stub Packages

Documentation Added

Implementation Plan (NEW)

Planned Features

Architecture Design

Key Components Specified

Editor Choice: CodeMirror 6

Implementation Phases

Stub JSON Format

Architecture Comparison

BasedPyright Browser Implementation

Custom Stub Package Integration

Recommendations

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