[`flake8-builtins`] Default to non-strict checking (`A005`) (#16125)

## Summary

This PR changes the default value of
`lint.flake8-builtins.builtins-strict-checking` added in
https://github.com/astral-sh/ruff/pull/15951 from `true` to `false`.
This also allows simplifying the default option logic and removes the
dependence on preview mode.

https://github.com/astral-sh/ruff/issues/15399 was already closed by
#15951, but this change will finalize the behavior mentioned in
https://github.com/astral-sh/ruff/issues/15399#issuecomment-2587017147.

As an example, strict checking flags modules based on their last
component, so `utils/logging.py` triggers A005. Non-strict checking
checks the path to the module, so `utils/logging.py` is allowed (this is
the example and desired behavior from #15399 exactly) but a top-level
`logging.py` or `logging/__init__.py` is still disallowed.

## Test Plan

Existing tests from #15951 and #16006, with the snapshot updated in
`a005_module_shadowing_strict_default` to reflect the new default.

crates/ruff/tests/lint.rs

@@ -2556,11 +2556,7 @@ fn a005_module_shadowing_strict_default() -> Result<()> {
         ----- stdout -----
         abc/__init__.py:1:1: A005 Module `abc` shadows a Python standard-library module
         collections/__init__.py:1:1: A005 Module `collections` shadows a Python standard-library module
-        collections/abc/__init__.py:1:1: A005 Module `abc` shadows a Python standard-library module
+        Found 2 errors.
-        foobar/abc/__init__.py:1:1: A005 Module `abc` shadows a Python standard-library module
-        foobar/collections/__init__.py:1:1: A005 Module `collections` shadows a Python standard-library module
-        foobar/collections/abc/__init__.py:1:1: A005 Module `abc` shadows a Python standard-library module
-        Found 6 errors.
 
         ----- stderr -----
         ");

crates/ruff/tests/snapshots/show_settings__display_default_settings.snap

@@ -231,7 +231,7 @@ linter.flake8_bandit.allowed_markup_calls = []
 linter.flake8_bugbear.extend_immutable_calls = []
 linter.flake8_builtins.allowed_modules = []
 linter.flake8_builtins.ignorelist = []
-linter.flake8_builtins.strict_checking = true
+linter.flake8_builtins.strict_checking = false
 linter.flake8_comprehensions.allow_dict_calls_with_keyword_arguments = false
 linter.flake8_copyright.notice_rgx = (?i)Copyright\s+((?:\(C\)|©)\s+)?\d{4}((-|,\s)\d{4})*
 linter.flake8_copyright.author = none

crates/ruff_linter/src/rules/flake8_builtins/rules/stdlib_module_shadowing.rs

@@ -23,12 +23,12 @@ use crate::settings::LinterSettings;
 /// Standard-library modules can be marked as exceptions to this rule via the
 /// [`lint.flake8-builtins.allowed-modules`] configuration option.
 ///
-/// By default, only the last component of the module name is considered, so `logging.py`,
+/// By default, the module path relative to the project root or [`src`] directories is considered,
-/// `utils/logging.py`, and `utils/logging/__init__.py` would all clash with the builtin `logging`
+/// so a top-level `logging.py` or `logging/__init__.py` will clash with the builtin `logging`
-/// module. With the [`lint.flake8-builtins.strict-checking`] option set to `false`, the module
+/// module, but `utils/logging.py`, for example, will not. With the
-/// path is considered, so only a top-level `logging.py` or `logging/__init__.py` will trigger the
+/// [`lint.flake8-builtins.builtins-strict-checking`] option set to `true`, only the last component
-/// rule and `utils/logging.py`, for example, would not. In preview mode, the default value of
+/// of the module name is considered, so `logging.py`, `utils/logging.py`, and
-/// [`lint.flake8-builtins.strict-checking`] is `false` rather than `true` in stable mode.
+/// `utils/logging/__init__.py` will all trigger the rule.
 ///
 /// This rule is not applied to stub files, as the name of a stub module is out
 /// of the control of the author of the stub file. Instead, a stub should aim to

crates/ruff_linter/src/rules/flake8_builtins/settings.rs

@@ -1,6 +1,6 @@
 //! Settings for the `flake8-builtins` plugin.
 
-use crate::{display_settings, settings::types::PreviewMode};
+use crate::display_settings;
 use ruff_macros::CacheKey;
 use std::fmt::{Display, Formatter};
 
@@ -11,16 +11,6 @@ pub struct Settings {
     pub strict_checking: bool,
 }
 
-impl Settings {
-    pub fn new(preview: PreviewMode) -> Self {
-        Self {
-            ignorelist: Vec::new(),
-            allowed_modules: Vec::new(),
-            strict_checking: preview.is_disabled(),
-        }
-    }
-}
-
 impl Display for Settings {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         display_settings! {

crates/ruff_workspace/src/configuration.rs

@@ -235,13 +235,6 @@ impl Configuration {
 
         let rules = lint.as_rule_table(lint_preview)?;
 
-        let flake8_builtins = lint
-            .flake8_builtins
-            .map(|builtins| builtins.into_settings(lint_preview))
-            .unwrap_or_else(|| {
-                ruff_linter::rules::flake8_builtins::settings::Settings::new(lint_preview)
-            });
-
         // LinterSettings validation
         let isort = lint
             .isort
@@ -344,7 +337,10 @@ impl Configuration {
                     .flake8_bugbear
                     .map(Flake8BugbearOptions::into_settings)
                     .unwrap_or_default(),
-                flake8_builtins,
+                flake8_builtins: lint
+                    .flake8_builtins
+                    .map(Flake8BuiltinsOptions::into_settings)
+                    .unwrap_or_default(),
                 flake8_comprehensions: lint
                     .flake8_comprehensions
                     .map(Flake8ComprehensionsOptions::into_settings)

crates/ruff_workspace/src/options.rs

@@ -28,7 +28,7 @@ use ruff_linter::rules::{
     pycodestyle, pydoclint, pydocstyle, pyflakes, pylint, pyupgrade, ruff,
 };
 use ruff_linter::settings::types::{
-    IdentifierPattern, OutputFormat, PreviewMode, PythonVersion, RequiredVersion,
+    IdentifierPattern, OutputFormat, PythonVersion, RequiredVersion,
 };
 use ruff_linter::{warn_user_once, RuleSelector};
 use ruff_macros::{CombineOptions, OptionsMetadata};
@@ -1267,9 +1267,9 @@ pub struct Flake8BuiltinsOptions {
     ///
     /// This option is ignored if both `strict-checking` and `builtins-strict-checking` are set.
     #[option(
-        default = r#"true"#,
+        default = r#"false"#,
         value_type = "bool",
-        example = "builtins-strict-checking = false"
+        example = "builtins-strict-checking = true"
     )]
     #[deprecated(
         since = "0.10.0",
@@ -1280,21 +1280,16 @@ pub struct Flake8BuiltinsOptions {
     /// Compare module names instead of full module paths.
     ///
     /// Used by [`A005` - `stdlib-module-shadowing`](https://docs.astral.sh/ruff/rules/stdlib-module-shadowing/).
-    ///
-    /// In preview mode the default value is `false` rather than `true`.
     #[option(
-        default = r#"true"#,
+        default = r#"false"#,
         value_type = "bool",
-        example = "strict-checking = false"
+        example = "strict-checking = true"
     )]
     pub strict_checking: Option<bool>,
 }
 
 impl Flake8BuiltinsOptions {
-    pub fn into_settings(
+    pub fn into_settings(self) -> ruff_linter::rules::flake8_builtins::settings::Settings {
-        self,
-        preview: PreviewMode,
-    ) -> ruff_linter::rules::flake8_builtins::settings::Settings {
         #[allow(deprecated)]
         ruff_linter::rules::flake8_builtins::settings::Settings {
             ignorelist: self
@@ -1309,7 +1304,7 @@ impl Flake8BuiltinsOptions {
                 .strict_checking
                 .or(self.builtins_strict_checking)
                 // use the old default of true on non-preview
-                .unwrap_or(preview.is_disabled()),
+                .unwrap_or_default(),
         }
     }
 }

crates/ruff_workspace/src/pyproject.rs

@@ -210,7 +210,7 @@ mod tests {
 
     use ruff_linter::codes;
     use ruff_linter::line_width::LineLength;
-    use ruff_linter::settings::types::{PatternPrefixPair, PreviewMode};
+    use ruff_linter::settings::types::PatternPrefixPair;
 
     use crate::options::{Flake8BuiltinsOptions, LintCommonOptions, LintOptions, Options};
     use crate::pyproject::{find_settings_toml, parse_pyproject_toml, Pyproject, Tools};
@@ -363,7 +363,7 @@ strict-checking = false
             })
         );
 
-        let settings = expected.into_settings(PreviewMode::Enabled);
+        let settings = expected.into_settings();
 
         assert_eq!(settings.allowed_modules, vec!["sys".to_string()]);
         assert_eq!(

ruff.schema.json

@@ -1086,7 +1086,7 @@
           }
         },
         "strict-checking": {
-          "description": "Compare module names instead of full module paths.\n\nUsed by [`A005` - `stdlib-module-shadowing`](https://docs.astral.sh/ruff/rules/stdlib-module-shadowing/).\n\nIn preview mode the default value is `false` rather than `true`.",
+          "description": "Compare module names instead of full module paths.\n\nUsed by [`A005` - `stdlib-module-shadowing`](https://docs.astral.sh/ruff/rules/stdlib-module-shadowing/).",
           "type": [
             "boolean",
             "null"