feat: first version

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

.flake8

@@ -1,6 +1,3 @@
 [flake8]
 extend-ignore = E203, E501, E722, B950
-select = C,E,F,W,T,B,B9,I
-per-file-ignores =
-    tests/*: T
-    noxfile.py: T
+extend-select = B9

.github/workflows/ci.yml

@@ -5,9 +5,7 @@ on:
   pull_request:
   push:
     branches:
-      - master
       - main
-      - develop
   release:
     types:
       - published
@@ -22,18 +20,16 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
       - uses: actions/setup-python@v4
         with:
-          python-version: "3.x"
+          python-version: "3.10"
       - uses: pre-commit/action@v3.0.0
         with:
           extra_args: --hook-stage manual --all-files
       - name: Run PyLint
         run: |
           echo "::add-matcher::$GITHUB_WORKSPACE/.github/matchers/pylint.json"
-          pipx run nox -s pylint
+          pipx run --python python nox -s pylint
 
   checks:
     name: Check Python ${{ matrix.python-version }} on ${{ matrix.runs-on }}
@@ -42,13 +38,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.7", "3.10"]
+        python-version: ["3.10", "3.11-dev"]
         runs-on: [ubuntu-latest, macos-latest, windows-latest]
 
-        include:
-          - python-version: pypy-3.8
-            runs-on: ubuntu-latest
-
     steps:
       - uses: actions/checkout@v3
         with:
@@ -62,7 +54,7 @@ jobs:
         run: python -m pip install .[test]
 
       - name: Test package
-        run: python -m pytest -ra --cov=flake8-errmsg
+        run: python -m pytest -ra
 
       - name: Upload coverage report
         uses: codecov/codecov-action@v3.1.0
@@ -87,10 +79,7 @@ jobs:
       - name: Check products
         run: pipx run twine check dist/*
 
-      - uses: pypa/gh-action-pypi-publish@v1.5.0
+      - uses: pypa/gh-action-pypi-publish@v1.5.1
         if: github.event_name == 'release' && github.event.action == 'published'
         with:
-          # Remember to generate this and set it in "GitHub Secrets"
           password: ${{ secrets.pypi_password }}
-          # Remove this line
-          repository_url: https://test.pypi.org/legacy/

.pre-commit-config.yaml

@@ -71,7 +71,6 @@ repos:
         exclude: docs/conf.py
         additional_dependencies: &flake8_dependencies
           - flake8-bugbear
-          - flake8-print
 
   - repo: https://github.com/pycqa/flake8
     rev: 5.0.4

README.md

@@ -1,29 +1,94 @@
 # flake8-errmsg
 
 [![Actions Status][actions-badge]][actions-link]
-[![Documentation Status][rtd-badge]][rtd-link]
+[![GitHub Discussion][github-discussions-badge]][github-discussions-link]
+[![Gitter][gitter-badge]][gitter-link]
 
 [![PyPI version][pypi-version]][pypi-link]
-[![Conda-Forge][conda-badge]][conda-link]
 [![PyPI platforms][pypi-platforms]][pypi-link]
 
-[![GitHub Discussion][github-discussions-badge]][github-discussions-link]
-[![Gitter][gitter-badge]][gitter-link]
+## Intro
+
+A checker for flake8 that helps format nice error messages. Currently there are
+two checks:
+
+- **EM101**: Check for raw usage of string literals in Exception raising.
+- **EM102**: Check for raw usage of f-string literals in Exception raising.
+
+The issue is that Python includes the line with the raise in the default
+traceback (and most other formatters, like Rich and IPython to too). That means
+a user gets a message like this:
+
+```python
+sub = "Some value"
+raise RuntimeError(f"{sub!r} is incorrect")
+```
+
+```pytb
+Traceback (most recent call last):
+  File "tmp.py", line 2, in <module>
+    raise RuntimeError(f"{sub!r} is incorrect")
+RuntimeError: 'Some value' is incorrect
+```
+
+If this is longer or more complex, the duplication can be quite confusing for a
+user unaccustomed to reading tracebacks.
+
+While if you always assign to something like `msg`, then you get:
+
+```python
+sub = "Some value"
+msg = f"{sub!r} is incorrect"
+raise RunetimeError(msg)
+```
+
+```pytb
+Traceback (most recent call last):
+  File "tmp.py", line 3, in <module>
+    raise RuntimeError(msg)
+RuntimeError: 'Some value' is incorrect
+```
+
+Now there's a simpler traceback, less code, and no double message. If you have a
+long message, this also often formats better when using Black, too.
+
+Reminder: Libraries should produce tracebacks with custom error classes, and
+applications should print nice errors, usually _without_ a traceback, unless
+something _unexpected_ occurred. An app should not print a traceback for an
+error that is known to be triggerable by a user.
+
+## Usage
+
+Just add this to your `.pre-commit-config.yaml` `flake8` check under
+`additional_dependencies`. If you use `extend-select`, you should need no other
+config.
+
+You can also manually run this check (without flake8's `noqa` filtering) via
+script entry-point (`pipx run flake8_errmsg <files>`) or module entry-point
+(`python -m flake8_errmsg <files>` when installed).
+
+## FAQ
+
+Q: Why not look for `"".format()` too? <br/> A: Tools like pyupgrade should help
+move to fstrings, so these should be rare. But it would likely be easy to add.
+
+Q: Why Python 3.10 only? <br/> A: This is a static checker and for developers.
+Developers and static checks should be on 3.10 already. And I was lazy and match
+statements are fantastic for this sort of thing. And the AST module changed in
+3.8 anyway.
 
+Q: What other sorts of checks are acceptable? <br/> A: Things that help with
+nice errors. For example, maybe requiring `raise SystemExit(n)` over `sys.exit`,
+`exit`, etc.
 
 <!-- prettier-ignore-start -->
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 [actions-link]:             https://github.com/henryiii/flake8-errmsg/actions
-[conda-badge]:              https://img.shields.io/conda/vn/conda-forge/flake8-errmsg
-[conda-link]:               https://github.com/conda-forge/flake8-errmsg-feedstock
 [github-discussions-badge]: https://img.shields.io/static/v1?label=Discussions&message=Ask&color=blue&logo=github
 [github-discussions-link]:  https://github.com/henryiii/flake8-errmsg/discussions
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 [gitter-link]:              https://gitter.im/https://github.com/henryiii/flake8-errmsg/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge
 [pypi-link]:                https://pypi.org/project/flake8-errmsg/
 [pypi-platforms]:           https://img.shields.io/pypi/pyversions/flake8-errmsg
 [pypi-version]:             https://badge.fury.io/py/flake8-errmsg.svg
-[rtd-badge]:                https://readthedocs.org/projects/flake8-errmsg/badge/?version=latest
-[rtd-link]:                 https://flake8-errmsg.readthedocs.io/en/latest/?badge=latest
-[sk-badge]:                 https://scikit-hep.org/assets/images/Scikit--HEP-Project-blue.svg
 <!-- prettier-ignore-end -->