feat: add check for .format() (#7)

Adding .format() check, minor testing related fixes.

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

.github/workflows/ci.yml

@@ -50,14 +50,13 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
 
-      - name: Install package
-        run: python -m pip install .[test]
+      - name: Install nox
+        run: python -m pip install nox
 
       - name: Test package
-        run: python -m pytest -ra
-
-      - name: Upload coverage report
-        uses: codecov/codecov-action@v3.1.0
+        run: |
+          nox -s tests
+          nox -s tests_flake8
 
   dist:
     name: Distribution build

.pre-commit-config.yaml

@@ -15,8 +15,6 @@ repos:
       - id: debug-statements
       - id: end-of-file-fixer
       - id: mixed-line-ending
-      - id: name-tests-test
-        args: ["--pytest-test-first"]
       - id: requirements-txt-fixer
       - id: trailing-whitespace
 

README.md

@@ -9,8 +9,10 @@
 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.
+- **EM101**: Check for raw usage of a string literal in Exception raising.
+- **EM102**: Check for raw usage of an f-string literal in Exception raising.
+- **EM103**: Check for raw usage of `.format` on a string literal 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
@@ -59,7 +61,8 @@ error that is known to be triggerable by a user.
 There is one option, `--errmsg-max-string-length`, which defaults to 0 but can
 be set to a larger value. The check will ignore string literals shorter than
 this length. This option is supported in configuration mode as well. This will
-only affect string literals and not f-strings.
+only affect string literals and not f-strings. This option is also supported
+when running directly, without flake8.
 
 ## Usage
 
@@ -73,9 +76,6 @@ script entry-point (`pipx run flake8-errmsg <files>`) or module entry-point
 
 ## 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

noxfile.py

@@ -39,7 +39,6 @@ def build(session: nox.Session) -> None:
     """
     Build an SDist and wheel.
     """
-
     session.install("build")
     session.run("python", "-m", "build")
 

src/flake8_errmsg/__init__.py

@@ -3,7 +3,7 @@
 """
 Copyright (c) 2022 Henry Schreiner. All rights reserved.
 
-flake8-errmsg: Flake8 checker for raw literals inside raises.
+flake8-errmsg: Flake8 checker for raw string literals inside raises.
 """
 
 from __future__ import annotations
@@ -18,7 +18,7 @@
 
 __all__ = ("__version__", "run_on_file", "main", "ErrMsgASTPlugin")
 
-__version__ = "0.3.0"
+__version__ = "0.4.0"
 
 
 class Flake8ASTErrorInfo(NamedTuple):
@@ -40,6 +40,13 @@ def visit_Raise(self, node: ast.Raise) -> None:
                     self.errors.append(EM101(node))
             case ast.Call(args=[ast.JoinedStr(), *_]):
                 self.errors.append(EM102(node))
+            case ast.Call(
+                args=[
+                    ast.Call(func=ast.Attribute(attr="format", value=ast.Constant())),
+                    *_,
+                ]
+            ):
+                self.errors.append(EM103(node))
             case _:
                 pass
 
@@ -54,19 +61,24 @@ def EM102(node: ast.AST) -> Flake8ASTErrorInfo:
     return Flake8ASTErrorInfo(node.lineno, node.col_offset, msg, Visitor)
 
 
+def EM103(node: ast.AST) -> Flake8ASTErrorInfo:
+    msg = "EM103 Exception must not use a .format() string directly, assign to variable first"
+    return Flake8ASTErrorInfo(node.lineno, node.col_offset, msg, Visitor)
+
+
 MAX_STRING_LENGTH = 0
 
 
 @dataclasses.dataclass
 class ErrMsgASTPlugin:
+    # Options have to be class variables in flake8 plugins
     max_string_length: ClassVar[int] = 0
 
     tree: ast.AST
 
     _: dataclasses.KW_ONLY
     name: str = "flake8_errmsg"
     version: str = "0.1.0"
-    options: Any = None
 
     def run(self) -> Iterator[Flake8ASTErrorInfo]:
         visitor = Visitor(self.max_string_length)

tests/example1.py

@@ -0,0 +1,15 @@
+from __future__ import annotations
+
+
+def f_a():
+    raise RuntimeError("This is an example exception")
+
+
+def f_b():
+    example = "example"
+    raise RuntimeError(f"This is an {example} exception")
+
+
+def f_c():
+    msg = "hello"
+    raise RuntimeError(msg)

tests/test_package.py

@@ -45,3 +45,19 @@ def test_string_length():
         results[0].msg
         == "EM102 Exception must not use an f-string literal, assign to variable first"
     )
+
+
+ERR2 = """\
+raise RuntimeError("this {} is".format("that"))
+"""
+
+
+def test_err2():
+    node = ast.parse(ERR2)
+    results = list(m.ErrMsgASTPlugin(node).run())
+    assert len(results) == 1
+    assert results[0].line_number == 1
+    assert (
+        results[0].msg
+        == "EM103 Exception must not use a .format() string directly, assign to variable first"
+    )