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pylint] C1901: compare-to-empty-string (#3405)
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19
crates/ruff/resources/test/fixtures/pylint/compare_to_empty_string.py
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,19 @@ | ||
| x = "a string" | ||
| y = "another string" | ||
| z = "" | ||
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| def errors(): | ||
| if x is "" or x == "": | ||
| print("x is an empty string") | ||
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| if y is not "" or y != "": | ||
| print("y is not an empty string") | ||
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| if "" != z: | ||
| print("z is an empty string") | ||
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| def ok(): | ||
| if x and not y: | ||
| print("x is not an empty string, but y is an empty string") |
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125 changes: 125 additions & 0 deletions
125
crates/ruff/src/rules/pylint/rules/compare_to_empty_string.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,125 @@ | ||
| use anyhow::bail; | ||
| use itertools::Itertools; | ||
| use rustpython_parser::ast::{Cmpop, Constant, Expr, ExprKind}; | ||
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| use ruff_diagnostics::{Diagnostic, Violation}; | ||
| use ruff_macros::{derive_message_formats, violation}; | ||
| use ruff_python_ast::helpers::{unparse_constant, unparse_expr}; | ||
| use ruff_python_ast::types::Range; | ||
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| use crate::checkers::ast::Checker; | ||
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| #[derive(Debug, PartialEq, Eq, Copy, Clone)] | ||
| pub enum EmptyStringCmpop { | ||
| Is, | ||
| IsNot, | ||
| Eq, | ||
| NotEq, | ||
| } | ||
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| impl TryFrom<&Cmpop> for EmptyStringCmpop { | ||
| type Error = anyhow::Error; | ||
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| fn try_from(value: &Cmpop) -> Result<Self, Self::Error> { | ||
| match value { | ||
| Cmpop::Is => Ok(Self::Is), | ||
| Cmpop::IsNot => Ok(Self::IsNot), | ||
| Cmpop::Eq => Ok(Self::Eq), | ||
| Cmpop::NotEq => Ok(Self::NotEq), | ||
| _ => bail!("{value:?} cannot be converted to EmptyStringCmpop"), | ||
| } | ||
| } | ||
| } | ||
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| impl EmptyStringCmpop { | ||
| pub fn into_unary(self) -> &'static str { | ||
| match self { | ||
| Self::Is | Self::Eq => "", | ||
| Self::IsNot | Self::NotEq => "not ", | ||
| } | ||
| } | ||
| } | ||
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| impl std::fmt::Display for EmptyStringCmpop { | ||
| fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { | ||
| let repr = match self { | ||
| Self::Is => "is", | ||
| Self::IsNot => "is not", | ||
| Self::Eq => "==", | ||
| Self::NotEq => "!=", | ||
| }; | ||
| write!(f, "{repr}") | ||
| } | ||
| } | ||
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| #[violation] | ||
| pub struct CompareToEmptyString { | ||
| pub existing: String, | ||
| pub replacement: String, | ||
| } | ||
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| impl Violation for CompareToEmptyString { | ||
| #[derive_message_formats] | ||
| fn message(&self) -> String { | ||
| format!( | ||
| "`{}` can be simplified to `{}` as an empty string is falsey", | ||
| self.existing, self.replacement, | ||
| ) | ||
| } | ||
| } | ||
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| pub fn compare_to_empty_string( | ||
| checker: &mut Checker, | ||
| left: &Expr, | ||
| ops: &[Cmpop], | ||
| comparators: &[Expr], | ||
| ) { | ||
| let mut first = true; | ||
| for ((lhs, rhs), op) in std::iter::once(left) | ||
| .chain(comparators.iter()) | ||
| .tuple_windows::<(&Expr<_>, &Expr<_>)>() | ||
| .zip(ops) | ||
| { | ||
| if let Ok(op) = EmptyStringCmpop::try_from(op) { | ||
| if std::mem::take(&mut first) { | ||
| // Check the left-most expression. | ||
| if let ExprKind::Constant { value, .. } = &lhs.node { | ||
| if let Constant::Str(s) = value { | ||
| if s.is_empty() { | ||
| let constant = unparse_constant(value, checker.stylist); | ||
| let expr = unparse_expr(rhs, checker.stylist); | ||
| let existing = format!("{constant} {op} {expr}"); | ||
| let replacement = format!("{}{expr}", op.into_unary()); | ||
| checker.diagnostics.push(Diagnostic::new( | ||
| CompareToEmptyString { | ||
| existing, | ||
| replacement, | ||
| }, | ||
| Range::from(lhs), | ||
| )); | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| // Check all right-hand expressions. | ||
| if let ExprKind::Constant { value, .. } = &rhs.node { | ||
| if let Constant::Str(s) = value { | ||
| if s.is_empty() { | ||
| let expr = unparse_expr(lhs, checker.stylist); | ||
| let constant = unparse_constant(value, checker.stylist); | ||
| let existing = format!("{expr} {op} {constant}"); | ||
| let replacement = format!("{}{expr}", op.into_unary()); | ||
| checker.diagnostics.push(Diagnostic::new( | ||
| CompareToEmptyString { | ||
| existing, | ||
| replacement, | ||
| }, | ||
| Range::from(rhs), | ||
| )); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |
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70 changes: 70 additions & 0 deletions
70
...ules/pylint/snapshots/ruff__rules__pylint__tests__PLC1901_compare_to_empty_string.py.snap
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,70 @@ | ||
| --- | ||
| source: crates/ruff/src/rules/pylint/mod.rs | ||
| expression: diagnostics | ||
| --- | ||
| - kind: | ||
| name: CompareToEmptyString | ||
| body: "`x is \"\"` can be simplified to `x` as an empty string is falsey" | ||
| suggestion: ~ | ||
| fixable: false | ||
| location: | ||
| row: 7 | ||
| column: 12 | ||
| end_location: | ||
| row: 7 | ||
| column: 14 | ||
| fix: ~ | ||
| parent: ~ | ||
| - kind: | ||
| name: CompareToEmptyString | ||
| body: "`x == \"\"` can be simplified to `x` as an empty string is falsey" | ||
| suggestion: ~ | ||
| fixable: false | ||
| location: | ||
| row: 7 | ||
| column: 23 | ||
| end_location: | ||
| row: 7 | ||
| column: 25 | ||
| fix: ~ | ||
| parent: ~ | ||
| - kind: | ||
| name: CompareToEmptyString | ||
| body: "`y is not \"\"` can be simplified to `not y` as an empty string is falsey" | ||
| suggestion: ~ | ||
| fixable: false | ||
| location: | ||
| row: 10 | ||
| column: 16 | ||
| end_location: | ||
| row: 10 | ||
| column: 18 | ||
| fix: ~ | ||
| parent: ~ | ||
| - kind: | ||
| name: CompareToEmptyString | ||
| body: "`y != \"\"` can be simplified to `not y` as an empty string is falsey" | ||
| suggestion: ~ | ||
| fixable: false | ||
| location: | ||
| row: 10 | ||
| column: 27 | ||
| end_location: | ||
| row: 10 | ||
| column: 29 | ||
| fix: ~ | ||
| parent: ~ | ||
| - kind: | ||
| name: CompareToEmptyString | ||
| body: "`\"\" != z` can be simplified to `not z` as an empty string is falsey" | ||
| suggestion: ~ | ||
| fixable: false | ||
| location: | ||
| row: 13 | ||
| column: 7 | ||
| end_location: | ||
| row: 13 | ||
| column: 9 | ||
| fix: ~ | ||
| parent: ~ | ||
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