Implement the pylint rule PLW1514 (unspecified-encoding)

crates/ruff_linter/resources/test/fixtures/pylint/unspecified_encoding.py

@@ -0,0 +1,44 @@
+import io
+import sys
+import tempfile
+import io as hugo
+import codecs
+
+# Errors.
+open("test.txt")
+io.TextIOWrapper(io.FileIO("test.txt"))
+hugo.TextIOWrapper(hugo.FileIO("test.txt"))
+tempfile.NamedTemporaryFile("w")
+tempfile.TemporaryFile("w")
+codecs.open("test.txt")
+tempfile.SpooledTemporaryFile(0, "w")
+
+# Non-errors.
+open("test.txt", encoding="utf-8")
+open("test.bin", "wb")
+open("test.bin", mode="wb")
+open("test.txt", "r", -1, "utf-8")
+open("test.txt", mode=sys.argv[1])
+
+def func(*args, **kwargs):
+    open(*args)
+    open("text.txt", **kwargs)
+
+io.TextIOWrapper(io.FileIO("test.txt"), encoding="utf-8")
+io.TextIOWrapper(io.FileIO("test.txt"), "utf-8")
+tempfile.TemporaryFile("w", encoding="utf-8")
+tempfile.TemporaryFile("w", -1, "utf-8")
+tempfile.TemporaryFile("wb")
+tempfile.TemporaryFile()
+tempfile.NamedTemporaryFile("w", encoding="utf-8")
+tempfile.NamedTemporaryFile("w", -1, "utf-8")
+tempfile.NamedTemporaryFile("wb")
+tempfile.NamedTemporaryFile()
+codecs.open("test.txt", encoding="utf-8")
+codecs.open("test.bin", "wb")
+codecs.open("test.bin", mode="wb")
+codecs.open("test.txt", "r", -1, "utf-8")
+tempfile.SpooledTemporaryFile(0, "w", encoding="utf-8")
+tempfile.SpooledTemporaryFile(0, "w", -1, "utf-8")
+tempfile.SpooledTemporaryFile(0, "wb")
+tempfile.SpooledTemporaryFile(0, )

crates/ruff_linter/src/checkers/ast/analyze/expression.rs

@@ -786,6 +786,9 @@ pub(crate) fn expression(expr: &Expr, checker: &mut Checker) {
             if checker.enabled(Rule::SubprocessRunWithoutCheck) {
                 pylint::rules::subprocess_run_without_check(checker, call);
             }
+            if checker.enabled(Rule::UnspecifiedEncoding) {
+                pylint::rules::unspecified_encoding(checker, call);
+            }
             if checker.any_enabled(&[
                 Rule::PytestRaisesWithoutException,
                 Rule::PytestRaisesTooBroad,

crates/ruff_linter/src/codes.rs

@@ -267,6 +267,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pylint, "W1508") => (RuleGroup::Stable, rules::pylint::rules::InvalidEnvvarDefault),
         (Pylint, "W1509") => (RuleGroup::Stable, rules::pylint::rules::SubprocessPopenPreexecFn),
         (Pylint, "W1510") => (RuleGroup::Stable, rules::pylint::rules::SubprocessRunWithoutCheck),
+        (Pylint, "W1514") => (RuleGroup::Preview, rules::pylint::rules::UnspecifiedEncoding),
         #[allow(deprecated)]
         (Pylint, "W1641") => (RuleGroup::Nursery, rules::pylint::rules::EqWithoutHash),
         (Pylint, "R0904") => (RuleGroup::Preview, rules::pylint::rules::TooManyPublicMethods),

crates/ruff_linter/src/rules/pylint/mod.rs

@@ -133,6 +133,7 @@ mod tests {
         Rule::SubprocessRunWithoutCheck,
         Path::new("subprocess_run_without_check.py")
     )]
+    #[test_case(Rule::UnspecifiedEncoding, Path::new("unspecified_encoding.py"))]
     #[test_case(Rule::BadDunderMethodName, Path::new("bad_dunder_method_name.py"))]
     #[test_case(Rule::NoSelfUse, Path::new("no_self_use.py"))]
     #[test_case(Rule::MisplacedBareRaise, Path::new("misplaced_bare_raise.py"))]

crates/ruff_linter/src/rules/pylint/rules/mod.rs

@@ -53,6 +53,7 @@ pub(crate) use type_name_incorrect_variance::*;
 pub(crate) use type_param_name_mismatch::*;
 pub(crate) use unexpected_special_method_signature::*;
 pub(crate) use unnecessary_direct_lambda_call::*;
+pub(crate) use unspecified_encoding::*;
 pub(crate) use useless_else_on_loop::*;
 pub(crate) use useless_import_alias::*;
 pub(crate) use useless_return::*;
@@ -114,6 +115,7 @@ mod type_name_incorrect_variance;
 mod type_param_name_mismatch;
 mod unexpected_special_method_signature;
 mod unnecessary_direct_lambda_call;
+mod unspecified_encoding;
 mod useless_else_on_loop;
 mod useless_import_alias;
 mod useless_return;

crates/ruff_linter/src/rules/pylint/rules/unspecified_encoding.rs

@@ -0,0 +1,157 @@
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast as ast;
+use ruff_python_ast::call_path::{format_call_path, CallPath};
+use ruff_text_size::Ranged;
+
+use crate::checkers::ast::Checker;
+
+/// ## What it does
+/// Checks for uses of `open` and related calls without an explicit `encoding`
+/// argument.
+///
+/// ## Why is this bad?
+/// Using `open` in text mode without an explicit encoding can lead to
+/// non-portable code, with differing behavior across platforms.
+///
+/// Instead, consider using the `encoding` parameter to enforce a specific
+/// encoding.
+///
+/// ## Example
+/// ```python
+/// open("file.txt")
+/// ```
+///
+/// Use instead:
+/// ```python
+/// open("file.txt", encoding="utf-8")
+/// ```
+///
+/// ## References
+/// - [Python documentation: `open`](https://docs.python.org/3/library/functions.html#open)
+#[violation]
+pub struct UnspecifiedEncoding {
+    function_name: String,
+    mode: Mode,
+}
+
+impl Violation for UnspecifiedEncoding {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let UnspecifiedEncoding {
+            function_name,
+            mode,
+        } = self;
+
+        match mode {
+            Mode::Supported => {
+                format!("`{function_name}` in text mode without explicit `encoding` argument")
+            }
+            Mode::Unsupported => {
+                format!("`{function_name}` without explicit `encoding` argument")
+            }
+        }
+    }
+}
+
+/// PLW1514
+pub(crate) fn unspecified_encoding(checker: &mut Checker, call: &ast::ExprCall) {
+    let Some((function_name, mode)) = checker
+        .semantic()
+        .resolve_call_path(&call.func)
+        .filter(|call_path| is_violation(call, call_path))
+        .map(|call_path| {
+            (
+                format_call_path(call_path.as_slice()),
+                Mode::from(&call_path),
+            )
+        })
+    else {
+        return;
+    };
+
+    checker.diagnostics.push(Diagnostic::new(
+        UnspecifiedEncoding {
+            function_name,
+            mode,
+        },
+        call.func.range(),
+    ));
+}
+
+/// Returns `true` if the given expression is a string literal containing a `b` character.
+fn is_binary_mode(expr: &ast::Expr) -> Option<bool> {
+    Some(expr.as_constant_expr()?.value.as_str()?.value.contains('b'))
+}
+
+/// Returns `true` if the given call lacks an explicit `encoding`.
+fn is_violation(call: &ast::ExprCall, call_path: &CallPath) -> bool {
+    // If we have something like `*args`, which might contain the encoding argument, abort.
+    if call
+        .arguments
+        .args
+        .iter()
+        .any(ruff_python_ast::Expr::is_starred_expr)
+    {
+        return false;
+    }
+    // If we have something like `**kwargs`, which might contain the encoding argument, abort.
+    if call
+        .arguments
+        .keywords
+        .iter()
+        .any(|keyword| keyword.arg.is_none())
+    {
+        return false;
+    }
+    match call_path.as_slice() {
+        ["" | "codecs" | "_io", "open"] => {
+            if let Some(mode_arg) = call.arguments.find_argument("mode", 1) {
+                if is_binary_mode(mode_arg).unwrap_or(true) {
+                    // binary mode or unknown mode is no violation
+                    return false;
+                }
+            }
+            // else mode not specified, defaults to text mode
+            call.arguments.find_argument("encoding", 3).is_none()
+        }
+        ["tempfile", "TemporaryFile" | "NamedTemporaryFile" | "SpooledTemporaryFile"] => {
+            let mode_pos = usize::from(call_path[1] == "SpooledTemporaryFile");
+            if let Some(mode_arg) = call.arguments.find_argument("mode", mode_pos) {
+                if is_binary_mode(mode_arg).unwrap_or(true) {
+                    // binary mode or unknown mode is no violation
+                    return false;
+                }
+            } else {
+                // defaults to binary mode
+                return false;
+            }
+            call.arguments
+                .find_argument("encoding", mode_pos + 2)
+                .is_none()
+        }
+        ["io" | "_io", "TextIOWrapper"] => call.arguments.find_argument("encoding", 1).is_none(),
+        _ => false,
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum Mode {
+    /// The call supports a `mode` argument.
+    Supported,
+    /// The call does not support a `mode` argument.
+    Unsupported,
+}
+
+impl From<&CallPath<'_>> for Mode {
+    fn from(value: &CallPath<'_>) -> Self {
+        match value.as_slice() {
+            ["" | "codecs" | "_io", "open"] => Mode::Supported,
+            ["tempfile", "TemporaryFile" | "NamedTemporaryFile" | "SpooledTemporaryFile"] => {
+                Mode::Supported
+            }
+            ["io" | "_io", "TextIOWrapper"] => Mode::Unsupported,
+            _ => Mode::Unsupported,
+        }
+    }
+}

crates/ruff_linter/src/rules/pylint/snapshots/ruff_linter__rules__pylint__tests__PLW1514_unspecified_encoding.py.snap

@@ -0,0 +1,72 @@
+---
+source: crates/ruff_linter/src/rules/pylint/mod.rs
+---
+unspecified_encoding.py:8:1: PLW1514 `open` in text mode without explicit `encoding` argument
+   |
+ 7 | # Errors.
+ 8 | open("test.txt")
+   | ^^^^ PLW1514
+ 9 | io.TextIOWrapper(io.FileIO("test.txt"))
+10 | hugo.TextIOWrapper(hugo.FileIO("test.txt"))
+   |
+
+unspecified_encoding.py:9:1: PLW1514 `io.TextIOWrapper` without explicit `encoding` argument
+   |
+ 7 | # Errors.
+ 8 | open("test.txt")
+ 9 | io.TextIOWrapper(io.FileIO("test.txt"))
+   | ^^^^^^^^^^^^^^^^ PLW1514
+10 | hugo.TextIOWrapper(hugo.FileIO("test.txt"))
+11 | tempfile.NamedTemporaryFile("w")
+   |
+
+unspecified_encoding.py:10:1: PLW1514 `io.TextIOWrapper` without explicit `encoding` argument
+   |
+ 8 | open("test.txt")
+ 9 | io.TextIOWrapper(io.FileIO("test.txt"))
+10 | hugo.TextIOWrapper(hugo.FileIO("test.txt"))
+   | ^^^^^^^^^^^^^^^^^^ PLW1514
+11 | tempfile.NamedTemporaryFile("w")
+12 | tempfile.TemporaryFile("w")
+   |
+
+unspecified_encoding.py:11:1: PLW1514 `tempfile.NamedTemporaryFile` in text mode without explicit `encoding` argument
+   |
+ 9 | io.TextIOWrapper(io.FileIO("test.txt"))
+10 | hugo.TextIOWrapper(hugo.FileIO("test.txt"))
+11 | tempfile.NamedTemporaryFile("w")
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ PLW1514
+12 | tempfile.TemporaryFile("w")
+13 | codecs.open("test.txt")
+   |
+
+unspecified_encoding.py:12:1: PLW1514 `tempfile.TemporaryFile` in text mode without explicit `encoding` argument
+   |
+10 | hugo.TextIOWrapper(hugo.FileIO("test.txt"))
+11 | tempfile.NamedTemporaryFile("w")
+12 | tempfile.TemporaryFile("w")
+   | ^^^^^^^^^^^^^^^^^^^^^^ PLW1514
+13 | codecs.open("test.txt")
+14 | tempfile.SpooledTemporaryFile(0, "w")
+   |
+
+unspecified_encoding.py:13:1: PLW1514 `codecs.open` in text mode without explicit `encoding` argument
+   |
+11 | tempfile.NamedTemporaryFile("w")
+12 | tempfile.TemporaryFile("w")
+13 | codecs.open("test.txt")
+   | ^^^^^^^^^^^ PLW1514
+14 | tempfile.SpooledTemporaryFile(0, "w")
+   |
+
+unspecified_encoding.py:14:1: PLW1514 `tempfile.SpooledTemporaryFile` in text mode without explicit `encoding` argument
+   |
+12 | tempfile.TemporaryFile("w")
+13 | codecs.open("test.txt")
+14 | tempfile.SpooledTemporaryFile(0, "w")
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PLW1514
+15 | 
+16 | # Non-errors.
+   |
+
+