stubpy 0.5.0

Generate .pyi stub files with full **kwargs / *args MRO backtracing

stubpy

Generate .pyi stub files for Python modules with full **kwargs / *args MRO backtracing, type-alias preservation, Generic support, overload stubs, package batch generation, and cross-file import resolution.

Features

• **kwargs backtracing — walks the entire MRO to expand **kwargs into concrete, named parameters at every inheritance level.
• cls() detection — @classmethod methods that forward **kwargs into cls(...) are resolved against cls.__init__, not MRO siblings.
• Typed *args preserved — explicitly annotated *args (e.g. *elements: Element) always survive the resolution chain.
• Positional-only / separator — def f(a, b, /, c) stubs correctly emit the PEP 570 / separator. Parent positional-only params absorbed by **kwargs are promoted to POSITIONAL_OR_KEYWORD to keep the child stub valid.
• TypeVar / Generic / overload — TypeVar, TypeAlias, NewType, ParamSpec, and TypeVarTuple declarations are re-emitted verbatim. Generic[T] bases are preserved via __orig_bases__. Each @overload variant gets its own stub; the concrete implementation is suppressed per PEP 484.
• Type-alias preservation — types.Length stays types.Length rather than expanding to str | float | int. Works inside Optional[...], tuple[...], list[...], and mixed unions.
• Cross-file imports — base classes and annotation types from other local modules are re-emitted in the .pyi header automatically.
• Package batch generation — generate_package() recursively stubs a whole directory tree, mirrors the structure, and creates __init__.pyi markers for every sub-package.
• Configuration file — stubpy.toml or [tool.stubpy] in pyproject.toml controls all options; CLI flags override file values.
• Typing style — "modern" (default, PEP 604 X | None) or "legacy" (Optional[X]) output.
• Execution modes — RUNTIME (default), AST_ONLY (no module execution), AUTO (runtime with graceful fallback).
• Structured diagnostics — every pipeline stage records INFO, WARNING, and ERROR entries rather than swallowing exceptions silently.
• Zero runtime dependencies — stdlib only.

---

Installation

pip install stubpy
# or
uv add stubpy

Requires Python 3.10+.

---

Quickstart

Single file

stubpy path/to/module.py              # writes module.pyi alongside source
stubpy path/to/module.py -o stubs/   # custom output path
stubpy path/to/module.py --print     # also print to stdout

Whole package

stubpy mypackage/                     # stubs written alongside source files
stubpy mypackage/ -o stubs/           # stubs written to stubs/
stubpy mypackage/ --typing-style legacy  # use Optional[X] instead of X | None

Configuration file

Place a stubpy.toml in the project root (or add [tool.stubpy] to pyproject.toml):

# stubpy.toml
include_private = false
typing_style    = "modern"     # "modern" (X | None) | "legacy" (Optional[X])
output_dir      = "stubs"
exclude         = ["**/test_*.py", "docs/conf.py"]

All flags have CLI equivalents; CLI flags override file values.

---

How it works

generate_stub(filepath)
    │
    ├─ 1. loader      load_module()                → module, path, name
    │        └─ (skipped in AST_ONLY; warning+fallback in AUTO)
    ├─ 2. ast_pass    ast_harvest()                → ASTSymbols
    ├─ 3. imports     scan_import_statements()     → import_map
    ├─ 4. aliases     build_alias_registry()       → ctx populated
    ├─ 5. symbols     build_symbol_table()         → SymbolTable
    ├─ 6. emitter     for each symbol (source order):
    │       ├─ AliasSymbol    → generate_alias_stub()
    │       ├─ ClassSymbol    → generate_class_stub()
    │       │       └─ for each method:
    │       │           resolver  resolve_params()       ← MRO backtracing
    │       │           emitter   generate_method_stub() ← raw AST annotations
    │       ├─ OverloadGroup → generate_overload_group_stub()
    │       ├─ FunctionSymbol → generate_function_stub()
    │       └─ VariableSymbol → generate_variable_stub()
    ├─ 7. imports     collect_typing_imports()     → header
    │                 collect_special_imports()
    │                 collect_cross_imports()
    └─ 8. write       .pyi written to disk

generate_package(package_dir, output_dir)
    └─ for each .py file: generate_stub(...)
    └─ ensure __init__.pyi for each sub-package

resolve_params uses three strategies in order:

1. No variadics — return own parameters unchanged.
2. cls() detection — AST-detect cls(..., **kwargs) in classmethods; resolve against cls.__init__.
3. MRO walk — collect concrete parameters from each ancestor until all variadics are resolved. POSITIONAL_ONLY params absorbed by **kwargs are promoted to POSITIONAL_OR_KEYWORD.

---

CLI reference

usage: stubpy [-h] [-o PATH] [--print] [--include-private] [--verbose]
              [--strict] [--typing-style {modern,legacy}]
              [--execution-mode {runtime,ast_only,auto}] [--no-config]
              path

positional arguments:
  path                  Python source file (.py) or package directory

optional arguments:
  -o PATH               Output .pyi path (file) or root directory (package)
  --print               Print generated stub to stdout (file mode only)
  --include-private     Include symbols starting with _
  --verbose             Print all diagnostics (INFO/WARNING/ERROR) to stderr
  --strict              Exit 1 if any ERROR diagnostic was recorded
  --typing-style STYLE  Output style: modern (X | None) or legacy (Optional[X])
  --execution-mode MODE runtime | ast_only | auto
  --no-config           Ignore stubpy.toml / pyproject.toml

---

Python API

from stubpy import generate_stub, generate_package, load_config, StubContext, StubConfig

# Single file
content = generate_stub("mymodule.py")
content = generate_stub("mymodule.py", "stubs/mymodule.pyi")

# Whole package
result = generate_package("mypackage/", "stubs/")
print(result.summary())   # "Generated 12 stubs, 0 failed."

# Custom config
cfg = StubConfig(typing_style="legacy", exclude=["**/migrations/*.py"])
result = generate_package("myapp/", "stubs/", config=cfg)

# Load config from file (stubpy.toml or pyproject.toml)
cfg = load_config(".")
result = generate_package("mypackage/", config=cfg)

Extended public API

# Context and configuration
from stubpy import StubContext, StubConfig, ExecutionMode, AliasEntry

# Diagnostics
from stubpy import DiagnosticCollector, DiagnosticLevel, DiagnosticStage, Diagnostic

# AST pre-pass
from stubpy import ast_harvest, ASTSymbols

# Symbol table
from stubpy import (
    SymbolTable, SymbolKind,
    ClassSymbol, FunctionSymbol, VariableSymbol, AliasSymbol, OverloadGroup,
    build_symbol_table,
)

# Emitters (public for extension)
from stubpy import (
    generate_class_stub, generate_function_stub, generate_variable_stub,
    generate_alias_stub, generate_overload_group_stub,
)

# Config file support
from stubpy import find_config_file, load_config

---

Example

# shapes.py
from typing import TypeVar, Generic, overload

T = TypeVar("T")

class Shape:
    def __init__(self, color: str = "black", opacity: float = 1.0) -> None: ...

class Circle(Shape):
    def __init__(self, radius: float, **kwargs) -> None:
        super().__init__(**kwargs)

    @classmethod
    def unit(cls, **kwargs) -> "Circle":
        return cls(radius=1.0, **kwargs)

class Box(Generic[T]):
    def put(self, item: T) -> None: ...
    def get(self) -> T: ...

@overload
def parse(x: int) -> int: ...
@overload
def parse(x: str) -> str: ...
def parse(x): return x

stubpy shapes.py --print

# shapes.pyi  (generated)
from __future__ import annotations
from typing import Generic, TypeVar, overload

T = TypeVar('T')

class Shape:
    def __init__(self, color: str = 'black', opacity: float = 1.0) -> None: ...

class Circle(Shape):
    def __init__(
        self,
        radius: float,
        color: str = 'black',
        opacity: float = 1.0,
    ) -> None: ...
    @classmethod
    def unit(cls, color: str = 'black', opacity: float = 1.0) -> Circle: ...

class Box(Generic[T]):
    def put(self, item: T) -> None: ...
    def get(self) -> T: ...

@overload
def parse(x: int) -> int: ...

@overload
def parse(x: str) -> str: ...

---

Project layout

stubpy/
├── stubpy/                 ← package (stdlib only, no runtime deps)
│   ├── context.py          StubContext, StubConfig, ExecutionMode
│   ├── diagnostics.py      DiagnosticCollector, Diagnostic
│   ├── ast_pass.py         ast_harvest, ASTSymbols
│   ├── symbols.py          SymbolTable, StubSymbol hierarchy
│   ├── loader.py           load_module
│   ├── aliases.py          build_alias_registry
│   ├── imports.py          scan / collect imports
│   ├── annotations.py      dispatch-table annotation_to_str
│   ├── resolver.py         resolve_params (MRO backtracing + pos-only normalisation)
│   ├── emitter.py          generate_class / method / function / alias / overload stubs
│   ├── generator.py        generate_stub + generate_package orchestrator
│   ├── config.py           find_config_file, load_config (TOML parsing)
│   └── __main__.py         CLI entry point
├── demo/                   demo package used for integration tests
├── tests/                  pytest suite (730+ tests)
│   ├── test_annotations.py
│   ├── test_ast_pass.py
│   ├── test_config.py
│   ├── test_context.py
│   ├── test_diagnostics.py
│   ├── test_emitter.py
│   ├── test_imports.py
│   ├── test_integration.py
│   ├── test_loader.py
│   ├── test_module_symbols.py
│   ├── test_resolver.py
│   ├── test_special_classes.py
│   └── test_symbols.py
├── docs/                   Sphinx + Furo documentation
├── LICENSE
└── pyproject.toml

---

Development setup

git clone https://github.com/wzjoriv/stubpy.git
cd stubpy
python3 -m venv .venv
source .venv/bin/activate      # Windows: .venv\Scripts\activate
pip install -e ".[dev]"
pytest

Build the docs:

pip install -e ".[docs]"
cd docs && make html
# open docs/_build/html/index.html

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License

MIT © 2026 Josue N Rivera