Initial commit

.github/workflows/build.yaml

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+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - '**'
+
+jobs:
+  build-and-publish:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        python_version: ['3.9']
+        os: [ubuntu-latest]
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Set up Python ${{ matrix.python_version }}
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python_version }}
+
+      - name: Install tox
+        run: |
+          python -m pip install --upgrade --upgrade-strategy eager tox
+
+      - name: Build and install wheel
+        run: |
+          tox run -m build
+          python -m pip install dist/*.whl

.github/workflows/release.yaml

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+name: CI
+
+on:
+  push:
+    tags:
+      - "[0-9]+.[0-9]+.[0-9]+*"
+
+jobs:
+  build-and-publish:
+    runs-on: ubuntu-latest
+    # Specifying a GitHub environment is optional, but strongly encouraged
+    environment: release
+    permissions:
+      # IMPORTANT: this permission is mandatory for trusted publishing
+      id-token: write
+      contents: write
+
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Set up Python 3.9
+        uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+
+      - name: Install tox
+        run: |
+          python -m pip install --upgrade --upgrade-strategy eager tox
+
+      - name: Build and install wheel
+        run: |
+          tox run -m build
+          python -m pip install dist/*.whl
+
+      - name: "Publish distribution 📦 to PyPI"
+        if: startsWith(github.ref, 'refs/tags/')
+        uses: pypa/gh-action-pypi-publish@release/v1
+
+      - name: Get release name
+        if: startsWith(github.ref, 'refs/tags/')
+        shell: bash
+        run: |
+          git fetch --depth=1 origin +refs/tags/*:refs/tags/* # github is dumb
+          echo "release_name=$(git tag -l --format "%(refname:strip=2): %(contents:lines=1)" ${{ github.ref_name }})" >> $GITHUB_ENV
+
+      - name: Release
+        uses: softprops/action-gh-release@v1
+        if: startsWith(github.ref, 'refs/tags/')
+        with:
+          name: "${{ env.release_name }}"
+          draft: false
+          files: |
+            dist/*.whl

.gitignore

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+# Covers JetBrains IDEs: IntelliJ, RubyMine, PhpStorm, AppCode, PyCharm, CLion
+
+*.iml
+
+## Directory-based project format:
+.idea/
+
+### Other editors
+.*.swp
+nbproject/
+.vscode
+
+*.exe
+*.zip
+
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# ruff
+.ruff_cache
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# for testing
+temp/
+tmp/

.pre-commit-config.yaml

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+repos:
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.5.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: check-yaml
+    -   id: debug-statements
+    -   id: double-quote-string-fixer
+    -   id: name-tests-test
+-   repo: https://github.com/asottile/reorder-python-imports
+    rev: v3.12.0
+    hooks:
+    -   id: reorder-python-imports
+        args: [--py38-plus, --add-import, 'from __future__ import annotations']
+-   repo: https://github.com/hhatto/autopep8
+    rev: v2.0.4
+    hooks:
+    -   id: autopep8
+-   repo: https://github.com/asottile/add-trailing-comma
+    rev: v3.1.0
+    hooks:
+    -   id: add-trailing-comma
+- repo: https://github.com/astral-sh/ruff-pre-commit
+  # Ruff version.
+  rev: v0.1.14
+  hooks:
+    - id: ruff
+      args: [ --fix ]
+-   repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v1.8.0
+    hooks:
+    -   id: mypy

LICENSE

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+Copyright (c) 2014 pre-commit dev team: Anthony Sottile, Ken Struys
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+[![build status](https://github.com/lordwelch/flake8-no-nested-comprehensions/actions/workflows/build.yaml/badge.svg)](https://github.com/lordwelch/flake8-no-nested-comprehensions/actions/workflows/build.yaml)
+[![pre-commit.ci status](https://results.pre-commit.ci/badge/github/lordwelch/flake8-no-nested-comprehensions/main.svg)](https://results.pre-commit.ci/latest/github/lordwelch/flake8-no-nested-comprehensions/main)
+
+flake8-no-nested-comprehensions
+================
+
+flake8 plugin which forbids nested comprehensions
+
+## installation
+
+```bash
+pip install flake8-no-nested-comprehensions
+```
+
+## flake8 codes
+
+| Code   | Description                      |
+|--------|----------------------------------|
+| CMP100 | do not use nested comprehensions |
+
+## rationale
+
+I don't like them.
+If you need them for performance you can put a `# noqa: CMP100` and preferrably put a comment in explaining it.
+
+## as a pre-commit hook
+
+See [pre-commit](https://github.com/pre-commit/pre-commit) for instructions
+
+Sample `.pre-commit-config.yaml`:
+
+```yaml
+-   repo: https://github.com/pycqa/flake8
+    rev: 3.8.1
+    hooks:
+    -   id: flake8
+        additional_dependencies: [flake8-no-nested-comprehensions==1.0.0]
+```

flake8_no_nested_comprehensions.py

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+from __future__ import annotations
+
+import ast
+import importlib.metadata
+from typing import Any
+from typing import TYPE_CHECKING
+
+
+if TYPE_CHECKING:  # pragma: no cover
+    import argparse
+    import flake8.options.manager
+    from collections.abc import Generator
+
+
+class Visitor(ast.NodeVisitor):
+    def __init__(self, max_generators: int) -> None:
+        self.problems: list[tuple[int, int]] = []
+        self.max_generators = max_generators
+
+        self.visit_ListComp = self._visit_max_generators
+        self.visit_SetComp = self._visit_max_generators
+        self.visit_GeneratorExp = self._visit_max_generators
+        self.visit_DictComp = self._visit_max_generators
+
+    def _visit_max_generators(self, node: ast.ListComp | ast.SetComp | ast.GeneratorExp | ast.DictComp) -> None:
+        if len(node.generators) > self.max_generators:
+            self.problems.append((node.lineno, node.col_offset))
+        self.generic_visit(node)
+
+
+class Plugin:
+    name = __name__
+    version = importlib.metadata.version(__name__)
+    max_generators = 1
+
+    def __init__(self, tree: ast.AST) -> None:
+        self._tree = tree
+
+    def add_options(manager: flake8.options.manager.OptionManager) -> None:  # pragma: no cover
+        manager.add_option(
+            '--max-comprehensions', type=int, metavar='n',
+            default=1, parse_from_config=True,
+            help='Maximum allowed generators in a single comprehension. (Default: %(default)s)',
+        )
+
+    @staticmethod
+    def parse_options(options: argparse.Namespace) -> None:  # pragma: no cover
+        Plugin.max_generators = options.max_comprehensions
+
+    def run(self) -> Generator[tuple[int, int, str, type[Any]], None, None]:
+        visitor = Visitor(self.max_generators)
+        visitor.visit(self._tree)
+        for line, col in visitor.problems:
+            yield line, col, 'CMP100 no nested comprehension', type(self)

pyproject.toml

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+[build-system]
+requires = ["setuptools>=61.2", "wheel", "setuptools_scm[toml]>=3.4"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "flake8_no_nested_comprehensions"
+description = "A flake8 plugin to disallow nested comprehensions"
+authors = [{name = "Timmy Welch", email = "timmy@narnian.us"}]
+license = {text = "MIT"}
+classifiers = [
+    "License :: OSI Approved :: MIT License",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3 :: Only",
+    "Programming Language :: Python :: Implementation :: CPython",
+    "Programming Language :: Python :: Implementation :: PyPy",
+]
+urls = {Homepage = "https://github.com/lordwelch/flake8_no_nested_comprehensions"}
+requires-python = ">=3.9"
+dependencies = ["flake8>4"]
+dynamic = ["version"]
+
+[project.readme]
+file = "README.md"
+content-type = "text/markdown"
+
+[tool.setuptools_scm]
+local_scheme = "no-local-version"
+
+[tool.setuptools]
+py-modules = ["flake8_no_nested_comprehensions"]
+include-package-data = true
+license-files = ["LICENSE"]
+
+[project.entry-points."flake8.extension"]
+CMP = "flake8_no_nested_comprehensions:Plugin"
+
+[tool.tox]
+legacy_tox_ini = """
+[tox:tox]
+envlist = py3.9
+
+[testenv]
+deps = -rrequirements-dev.txt
+commands =
+    coverage erase
+    coverage run -m pytest {posargs:tests}
+    coverage report
+
+[testenv:wheel]
+description = Generate wheel and tar.gz
+labels =
+    release
+    build
+skip_install = true
+deps =
+    build
+commands_pre =
+    -python -c 'import shutil,pathlib; \
+    shutil.rmtree("./build/", ignore_errors=True); \
+    shutil.rmtree("./dist/", ignore_errors=True)'
+commands =
+    python -m build
+
+[testenv:pypi-upload]
+description = Upload wheel to PyPi
+platform = Linux
+labels =
+    release
+skip_install = true
+depends = wheel
+deps =
+    twine
+passenv =
+    TWINE_*
+setenv =
+    TWINE_NON_INTERACTIVE=true
+commands =
+    python -m twine upload dist/*.whl dist/*.tar.gz
+"""
+
+
+[tool.pep8]
+ignore = "E265,E501"
+max_line_length = "120"
+
+[tool.autopep8]
+max_line_length = 120
+ignore = "E265,E501"
+
+[tool.mypy]
+check_untyped_defs = true
+disallow_any_generics = true
+warn_return_any = false
+disallow_incomplete_defs = true
+disallow_untyped_defs = true
+no_implicit_optional = true
+warn_redundant_casts = true
+warn_unused_ignores = true
+disable_error_code = ['method-assign']
+
+[[tool.mypy.overrides]]
+module = ["testing.*"]
+warn_return_any = false
+disallow_untyped_defs = false
+
+[[tool.mypy.overrides]]
+module = ["tests.*"]
+warn_return_any = false
+disallow_untyped_defs = false
+
+[tool.ruff]
+line-length = 120
+extend-safe-fixes = ["TCH"]
+extend-select = ["COM812", "TCH"]

requirements-dev.txt

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+build
+covdefaults
+coverage
+pytest
+tox

tests/no_nested_comprehensions_test.py

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+from __future__ import annotations
+
+import ast
+
+from flake8_no_nested_comprehensions import Plugin
+
+
+def _results(s: str) -> set[str]:
+    tree = ast.parse(s)
+    plugin = Plugin(tree)
+    return {f'{line}:{col} {msg}' for line, col, msg, _ in plugin.run()}
+
+
+def test_trivial_case() -> None:
+    assert _results('') == set()
+
+
+def test_nested_comprehension() -> None:
+    ret = _results('[attr for style in styles for attr in {"testing", "set"}]')
+    assert ret == {'1:0 CMP100 no nested comprehension'}
+
+
+def test_allowed_comprehension() -> None:
+    ret = _results('[style for style in {"testing", "set"}]')
+    assert ret == set()