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[flake8-errmsg] Exclude typing.cast from EM101 #19656

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Merged
ntBre merged 2 commits into from
Aug 1, 2025
Merged

[flake8-errmsg] Exclude typing.cast from EM101 #19656

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f1923ea
fix-19596
danparizher Jul 31, 2025
1c20c79
combine destructuring patterns
danparizher Jul 31, 2025
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22 changes: 22 additions & 0 deletions crates/ruff_linter/resources/test/fixtures/flake8_errmsg/EM.py
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Original file line number Diff line number Diff line change
Expand Up @@ -88,3 +88,25 @@ def f_multi_line_string2():
example="example"
)
)


def raise_typing_cast_exception():
import typing
raise typing.cast("Exception", None)


def f_typing_cast_excluded():
from typing import cast
raise cast(RuntimeError, "This should not trigger EM101")


def f_typing_cast_excluded_import():
import typing
raise typing.cast(RuntimeError, "This should not trigger EM101")


def f_typing_cast_excluded_aliased():
from typing import cast as my_cast
raise my_cast(RuntimeError, "This should not trigger EM101")


137 changes: 69 additions & 68 deletions crates/ruff_linter/src/rules/flake8_errmsg/rules/string_in_exception.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -182,60 +182,47 @@ impl Violation for DotFormatInException {

/// EM101, EM102, EM103
pub(crate) fn string_in_exception(checker: &Checker, stmt: &Stmt, exc: &Expr) {
if let Expr::Call(ast::ExprCall {
let Expr::Call(ast::ExprCall {
func,
arguments: Arguments { args, .. },
..
}) = exc
{
if let Some(first) = args.first() {
match first {
// Check for string literals.
Expr::StringLiteral(ast::ExprStringLiteral { value: string, .. }) => {
if checker.is_rule_enabled(Rule::RawStringInException) {
if string.len() >= checker.settings().flake8_errmsg.max_string_length {
let mut diagnostic =
checker.report_diagnostic(RawStringInException, first.range());
if let Some(indentation) =
whitespace::indentation(checker.source(), stmt)
{
diagnostic.set_fix(generate_fix(
stmt,
first,
indentation,
checker.stylist(),
checker.locator(),
));
}
}
}
}
// Check for byte string literals.
Expr::BytesLiteral(ast::ExprBytesLiteral { value: bytes, .. }) => {
if checker.settings().rules.enabled(Rule::RawStringInException) {
if bytes.len() >= checker.settings().flake8_errmsg.max_string_length
&& is_raise_exception_byte_string_enabled(checker.settings())
{
let mut diagnostic =
checker.report_diagnostic(RawStringInException, first.range());
if let Some(indentation) =
whitespace::indentation(checker.source(), stmt)
{
diagnostic.set_fix(generate_fix(
stmt,
first,
indentation,
checker.stylist(),
checker.locator(),
));
}
else {
return;
};

if checker.semantic().match_typing_expr(func, "cast") {
return;
}

if let Some(first) = args.first() {
match first {
// Check for string literals.
Expr::StringLiteral(ast::ExprStringLiteral { value: string, .. }) => {
if checker.is_rule_enabled(Rule::RawStringInException) {
if string.len() >= checker.settings().flake8_errmsg.max_string_length {
let mut diagnostic =
checker.report_diagnostic(RawStringInException, first.range());
if let Some(indentation) = whitespace::indentation(checker.source(), stmt) {
diagnostic.set_fix(generate_fix(
stmt,
first,
indentation,
checker.stylist(),
checker.locator(),
));
}
}
}
// Check for f-strings.
Expr::FString(_) => {
if checker.is_rule_enabled(Rule::FStringInException) {
}
// Check for byte string literals.
Expr::BytesLiteral(ast::ExprBytesLiteral { value: bytes, .. }) => {
if checker.settings().rules.enabled(Rule::RawStringInException) {
if bytes.len() >= checker.settings().flake8_errmsg.max_string_length
&& is_raise_exception_byte_string_enabled(checker.settings())
{
let mut diagnostic =
checker.report_diagnostic(FStringInException, first.range());
checker.report_diagnostic(RawStringInException, first.range());
if let Some(indentation) = whitespace::indentation(checker.source(), stmt) {
diagnostic.set_fix(generate_fix(
stmt,
Expand All @@ -247,32 +234,46 @@ pub(crate) fn string_in_exception(checker: &Checker, stmt: &Stmt, exc: &Expr) {
}
}
}
// Check for .format() calls.
Expr::Call(ast::ExprCall { func, .. }) => {
if checker.is_rule_enabled(Rule::DotFormatInException) {
if let Expr::Attribute(ast::ExprAttribute { value, attr, .. }) =
func.as_ref()
{
if attr == "format" && value.is_literal_expr() {
let mut diagnostic =
checker.report_diagnostic(DotFormatInException, first.range());
if let Some(indentation) =
whitespace::indentation(checker.source(), stmt)
{
diagnostic.set_fix(generate_fix(
stmt,
first,
indentation,
checker.stylist(),
checker.locator(),
));
}
}
// Check for f-strings.
Expr::FString(_) => {
if checker.is_rule_enabled(Rule::FStringInException) {
let mut diagnostic =
checker.report_diagnostic(FStringInException, first.range());
if let Some(indentation) = whitespace::indentation(checker.source(), stmt) {
diagnostic.set_fix(generate_fix(
stmt,
first,
indentation,
checker.stylist(),
checker.locator(),
));
}
}
}
// Check for .format() calls.
Expr::Call(ast::ExprCall { func, .. }) => {
if checker.is_rule_enabled(Rule::DotFormatInException) {
if let Expr::Attribute(ast::ExprAttribute { value, attr, .. }) = func.as_ref() {
if attr == "format" && value.is_literal_expr() {
let mut diagnostic =
checker.report_diagnostic(DotFormatInException, first.range());
if let Some(indentation) =
whitespace::indentation(checker.source(), stmt)
{
diagnostic.set_fix(generate_fix(
stmt,
first,
indentation,
checker.stylist(),
checker.locator(),
));
}
}
}
}
_ => {}
}
_ => {}
}
}
}
Expand Down
3 changes: 3 additions & 0 deletions ...r/src/rules/flake8_errmsg/snapshots/ruff_linter__rules__flake8_errmsg__tests__custom.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -278,3 +278,6 @@ EM.py:84:9: EM103 [*] Exception must not use a `.format()` string directly, assi
91 |+ raise RuntimeError(
92 |+ msg
93 |+ )
91 94 |
92 95 |
93 96 | def raise_typing_cast_exception():
3 changes: 3 additions & 0 deletions ...src/rules/flake8_errmsg/snapshots/ruff_linter__rules__flake8_errmsg__tests__defaults.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -343,3 +343,6 @@ EM.py:84:9: EM103 [*] Exception must not use a `.format()` string directly, assi
91 |+ raise RuntimeError(
92 |+ msg
93 |+ )
91 94 |
92 95 |
93 96 | def raise_typing_cast_exception():
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