monty-typeshed

The vendored typeshed subset that powers type checking in Monty.

Monty implements a deliberately small subset of Python's stdlib. Its type checker (the monty-type-checking crate, powered by ty) therefore needs stubs that describe Monty's runtime surface rather than CPython's: code using an unsupported builtin or stdlib module should fail type checking up front, not pass the checker and then fail at runtime. This crate vendors only the stubs for what Monty supports, with unsupported functions and classes filtered out.

Originally derived from ruff's ty_vendored crate.

Layout

• vendor/typeshed/ — the vendored stubs, derived from upstream typeshed at the commit recorded in vendor/typeshed/source_commit.txt (exposed as SOURCE_COMMIT). Do not edit these files manually — they are overwritten wholesale by the update script.
• custom/ — hand-written stubs that override or supplement upstream files where Monty's surface intentionally differs (e.g. asyncio, os, sys, unicodedata). The update script copies them into vendor/typeshed/stdlib.
• update.py — clones upstream typeshed, filters the stubs down to the builtins and modules Monty supports (whitelists in the script mirror crates/monty/src/builtins/), and applies the custom/ overrides. Run it via make update-typeshed from the workspace root.
• build.rs — zips the vendored stubs into the compiled binary at build time, so Monty ships type checking with no files on disk.

API

The crate exposes a single entry point: file_system() returns a static ruff_db VendoredFileSystem over the zipped stubs, which monty-type-checking uses as the search path for stdlib module resolution.

let typeshed = monty_typeshed::file_system();
assert!(typeshed.exists("stdlib/builtins.pyi"));

Monty crates

• monty — the core interpreter: Python parser, bytecode VM, and sandbox.
• monty-types — the shared boundary data types (values, exceptions, OS calls, resource limits) hosts use without linking the interpreter.
• monty-fs — host-side filesystem mounts: maps virtual sandbox paths to real host directories.
• monty-runtime — the monty binary: REPL, file runner, and subprocess worker mode.
• monty-pool — an elastic pool of crash-isolated monty worker subprocesses.
• monty-proto — the protobuf wire protocol spoken between pool parents and workers.
• monty-type-checking — type checking of sandboxed code, powered by ty.
• monty-typeshed — the trimmed typeshed stubs describing the stdlib subset Monty implements. this crate
• monty-macros — the proc macros behind monty's argument parsing.