[flake8-datetimez] Usages of datetime.max/datetime.min (DTZ901)

crates/ruff_linter/resources/test/fixtures/flake8_datetimez/DTZ901.py

@@ -0,0 +1,30 @@
+import datetime
+
+
+# Error
+datetime.datetime.max
+datetime.datetime.min
+
+datetime.datetime.max.replace(year=...)
+datetime.datetime.min.replace(hour=...)
+
+
+# No error
+datetime.datetime.max.replace(tzinfo=...)
+datetime.datetime.min.replace(tzinfo=...)
+
+
+from datetime import datetime
+
+
+# Error
+datetime.max
+datetime.min
+
+datetime.max.replace(year=...)
+datetime.min.replace(hour=...)
+
+
+# No error
+datetime.max.replace(tzinfo=...)
+datetime.min.replace(tzinfo=...)

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

@@ -339,6 +339,9 @@ pub(crate) fn expression(expr: &Expr, checker: &mut Checker) {
             if checker.enabled(Rule::SixPY3) {
                 flake8_2020::rules::name_or_attribute(checker, expr);
             }
+            if checker.enabled(Rule::DatetimeMaxMin) {
+                flake8_datetimez::rules::datetime_max_min(checker, expr);
+            }
             if checker.enabled(Rule::BannedApi) {
                 flake8_tidy_imports::rules::banned_attribute_access(checker, expr);
             }

crates/ruff_linter/src/codes.rs

@@ -706,6 +706,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Flake8Datetimez, "007") => (RuleGroup::Stable, rules::flake8_datetimez::rules::CallDatetimeStrptimeWithoutZone),
         (Flake8Datetimez, "011") => (RuleGroup::Stable, rules::flake8_datetimez::rules::CallDateToday),
         (Flake8Datetimez, "012") => (RuleGroup::Stable, rules::flake8_datetimez::rules::CallDateFromtimestamp),
+        (Flake8Datetimez, "901") => (RuleGroup::Preview, rules::flake8_datetimez::rules::DatetimeMaxMin),
 
         // pygrep-hooks
         (PygrepHooks, "001") => (RuleGroup::Removed, rules::pygrep_hooks::rules::Eval),

crates/ruff_linter/src/rules/flake8_datetimez/mod.rs

@@ -9,6 +9,7 @@ mod tests {
     use test_case::test_case;
 
     use crate::registry::Rule;
+    use crate::settings::types::PreviewMode;
     use crate::test::test_path;
     use crate::{assert_messages, settings};
 
@@ -30,4 +31,18 @@ mod tests {
         assert_messages!(snapshot, diagnostics);
         Ok(())
     }
+
+    #[test_case(Rule::DatetimeMaxMin, Path::new("DTZ901.py"))]
+    fn preview_rules(rule_code: Rule, path: &Path) -> Result<()> {
+        let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());
+        let diagnostics = test_path(
+            Path::new("flake8_datetimez").join(path).as_path(),
+            &settings::LinterSettings {
+                preview: PreviewMode::Enabled,
+                ..settings::LinterSettings::for_rule(rule_code)
+            },
+        )?;
+        assert_messages!(snapshot, diagnostics);
+        Ok(())
+    }
 }

crates/ruff_linter/src/rules/flake8_datetimez/rules/datetime_max_min.rs

@@ -0,0 +1,120 @@
+use crate::checkers::ast::Checker;
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::{Expr, ExprAttribute, ExprCall};
+use ruff_python_semantic::Modules;
+use ruff_text_size::Ranged;
+use std::fmt::{Display, Formatter};
+
+#[derive(Debug, Eq, PartialEq)]
+enum MaxMin {
+    /// `datetime.datetime.max`
+    Max,
+    /// `datetime.datetime.min`
+    Min,
+}
+
+impl MaxMin {
+    fn from(attr: &str) -> Self {
+        match attr {
+            "max" => Self::Max,
+            "min" => Self::Min,
+            _ => panic!("Unexpected argument for MaxMin"),
+        }
+    }
+}
+
+impl Display for MaxMin {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        let name = match self {
+            MaxMin::Max => "max",
+            MaxMin::Min => "min",
+        };
+
+        write!(f, "{name}")
+    }
+}
+
+/// ## What it does
+/// Checks for usages of `datetime.datetime.max` and `datetime.datetime.min`.
+///
+/// ## Why is this bad?
+/// `datetime.max` and `datetime.min` are constants with no timezone information.
+/// Therefore, operations on them might fail unexpectedly:
+///
+/// ```python
+/// # Timezone: UTC-14
+/// datetime.max.timestamp()  # ValueError: year 10000 is out of range
+/// datetime.min.timestamp()  # ValueError: year 0 is out of range
+/// ```
+///
+/// ## Example
+/// ```python
+/// datetime.max
+/// ```
+///
+/// Use instead:
+/// ```python
+/// datetime.max.replace(tzinfo=datetime.UTC)
+/// ```
+#[violation]
+pub struct DatetimeMaxMin(MaxMin);
+
+impl Violation for DatetimeMaxMin {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        format!("`datetime.datetime.{}` used", self.0)
+    }
+
+    fn fix_title(&self) -> Option<String> {
+        Some(format!(
+            "Use `datetime.datetime.{}.replace(tzinfo=...)` instead",
+            self.0
+        ))
+    }
+}
+
+/// DTZ901
+pub(crate) fn datetime_max_min(checker: &mut Checker, expr: &Expr) {
+    let semantic = checker.semantic();
+
+    if !semantic.seen_module(Modules::DATETIME) {
+        return;
+    }
+
+    let Some(qualified_name) = semantic.resolve_qualified_name(expr) else {
+        return;
+    };
+
+    let maxmin = match qualified_name.segments() {
+        ["datetime", "datetime", attr @ ("max" | "min")] => MaxMin::from(attr),
+        _ => return,
+    };
+
+    if followed_by_replace_tzinfo(checker) {
+        return;
+    }
+
+    let diagnostic = Diagnostic::new(DatetimeMaxMin(maxmin), expr.range());
+
+    checker.diagnostics.push(diagnostic);
+}
+
+/// Check if the current expression has the pattern `foo.replace(tzinfo=bar)`.
+pub(super) fn followed_by_replace_tzinfo(checker: &Checker) -> bool {
+    let semantic = checker.semantic();
+
+    let Some(parent) = semantic.current_expression_parent() else {
+        return false;
+    };
+    let Some(grandparent) = semantic.current_expression_grandparent() else {
+        return false;
+    };
+
+    match (parent, grandparent) {
+        (Expr::Attribute(ExprAttribute { attr, .. }), Expr::Call(ExprCall { arguments, .. })) => {
+            attr.as_str() == "replace" && matches!(arguments.find_keyword("tzinfo"), Some(..))
+        }
+        _ => false,
+    }
+}

crates/ruff_linter/src/rules/flake8_datetimez/rules/helpers.rs

@@ -8,10 +8,10 @@ pub(super) enum DatetimeModuleAntipattern {
     NonePassedToTzArgument,
 }
 
-/// Check if the parent expression is a call to `astimezone`. This assumes that
-/// the current expression is a `datetime.datetime` object.
+/// Check if the parent expression is a call to `astimezone`.
+/// This assumes that the current expression is a `datetime.datetime` object.
 pub(super) fn parent_expr_is_astimezone(checker: &Checker) -> bool {
-    checker.semantic().current_expression_parent().is_some_and( |parent| {
+    checker.semantic().current_expression_parent().is_some_and(|parent| {
         matches!(parent, Expr::Attribute(ExprAttribute { attr, .. }) if attr.as_str() == "astimezone")
     })
 }

crates/ruff_linter/src/rules/flake8_datetimez/rules/mod.rs

@@ -7,6 +7,7 @@ pub(crate) use call_datetime_today::*;
 pub(crate) use call_datetime_utcfromtimestamp::*;
 pub(crate) use call_datetime_utcnow::*;
 pub(crate) use call_datetime_without_tzinfo::*;
+pub(crate) use datetime_max_min::*;
 
 mod call_date_fromtimestamp;
 mod call_date_today;
@@ -17,4 +18,5 @@ mod call_datetime_today;
 mod call_datetime_utcfromtimestamp;
 mod call_datetime_utcnow;
 mod call_datetime_without_tzinfo;
+mod datetime_max_min;
 mod helpers;

crates/ruff_linter/src/rules/flake8_datetimez/snapshots/ruff_linter__rules__flake8_datetimez__tests__DTZ901_DTZ901.py.snap

@@ -0,0 +1,79 @@
+---
+source: crates/ruff_linter/src/rules/flake8_datetimez/mod.rs
+snapshot_kind: text
+---
+DTZ901.py:5:1: DTZ901 `datetime.datetime.max` used
+  |
+4 | # Error
+5 | datetime.datetime.max
+  | ^^^^^^^^^^^^^^^^^^^^^ DTZ901
+6 | datetime.datetime.min
+  |
+  = help: Use `datetime.datetime.max.replace(tzinfo=...)` instead
+
+DTZ901.py:6:1: DTZ901 `datetime.datetime.min` used
+  |
+4 | # Error
+5 | datetime.datetime.max
+6 | datetime.datetime.min
+  | ^^^^^^^^^^^^^^^^^^^^^ DTZ901
+7 | 
+8 | datetime.datetime.max.replace(year=...)
+  |
+  = help: Use `datetime.datetime.min.replace(tzinfo=...)` instead
+
+DTZ901.py:8:1: DTZ901 `datetime.datetime.max` used
+  |
+6 | datetime.datetime.min
+7 | 
+8 | datetime.datetime.max.replace(year=...)
+  | ^^^^^^^^^^^^^^^^^^^^^ DTZ901
+9 | datetime.datetime.min.replace(hour=...)
+  |
+  = help: Use `datetime.datetime.max.replace(tzinfo=...)` instead
+
+DTZ901.py:9:1: DTZ901 `datetime.datetime.min` used
+  |
+8 | datetime.datetime.max.replace(year=...)
+9 | datetime.datetime.min.replace(hour=...)
+  | ^^^^^^^^^^^^^^^^^^^^^ DTZ901
+  |
+  = help: Use `datetime.datetime.min.replace(tzinfo=...)` instead
+
+DTZ901.py:21:1: DTZ901 `datetime.datetime.max` used
+   |
+20 | # Error
+21 | datetime.max
+   | ^^^^^^^^^^^^ DTZ901
+22 | datetime.min
+   |
+   = help: Use `datetime.datetime.max.replace(tzinfo=...)` instead
+
+DTZ901.py:22:1: DTZ901 `datetime.datetime.min` used
+   |
+20 | # Error
+21 | datetime.max
+22 | datetime.min
+   | ^^^^^^^^^^^^ DTZ901
+23 | 
+24 | datetime.max.replace(year=...)
+   |
+   = help: Use `datetime.datetime.min.replace(tzinfo=...)` instead
+
+DTZ901.py:24:1: DTZ901 `datetime.datetime.max` used
+   |
+22 | datetime.min
+23 | 
+24 | datetime.max.replace(year=...)
+   | ^^^^^^^^^^^^ DTZ901
+25 | datetime.min.replace(hour=...)
+   |
+   = help: Use `datetime.datetime.max.replace(tzinfo=...)` instead
+
+DTZ901.py:25:1: DTZ901 `datetime.datetime.min` used
+   |
+24 | datetime.max.replace(year=...)
+25 | datetime.min.replace(hour=...)
+   | ^^^^^^^^^^^^ DTZ901
+   |
+   = help: Use `datetime.datetime.min.replace(tzinfo=...)` instead