Add config option to disable typing_extensions imports (#17611)

Summary
--

This PR resolves https://github.com/astral-sh/ruff/issues/9761 by adding
a linter configuration option to disable
`typing_extensions` imports. As mentioned [here], it would be ideal if
we could
detect whether or not `typing_extensions` is available as a dependency
automatically, but this seems like a much easier fix in the meantime.

The default for the new option, `typing-extensions`, is `true`,
preserving the current behavior. Setting it to `false` will bail out of
the new
`Checker::typing_importer` method, which has been refactored from the 
`Checker::import_from_typing` method in
https://github.com/astral-sh/ruff/pull/17340),
with `None`, which is then handled specially by each rule that calls it.

I considered some alternatives to a config option, such as checking if
`typing_extensions` has been imported or checking for a `TYPE_CHECKING`
block we could use, but I think defaulting to allowing
`typing_extensions` imports and allowing the user to disable this with
an option is both simple to implement and pretty intuitive.

[here]:
https://github.com/astral-sh/ruff/issues/9761#issuecomment-2790492853

Test Plan
--

New linter tests exercising several combinations of Python versions and
the new config option for PYI019. I also added tests for the other
affected rules, but only in the case where the new config option is
enabled. The rules' existing tests also cover the default case.

crates/ruff_workspace/src/configuration.rs

@@ -430,6 +430,7 @@ impl Configuration {
                     .ruff
                     .map(RuffOptions::into_settings)
                     .unwrap_or_default(),
+                typing_extensions: lint.typing_extensions.unwrap_or(true),
             },
 
             formatter,
@@ -633,6 +634,7 @@ pub struct LintConfiguration {
     pub logger_objects: Option<Vec<String>>,
     pub task_tags: Option<Vec<String>>,
     pub typing_modules: Option<Vec<String>>,
+    pub typing_extensions: Option<bool>,
 
     // Plugins
     pub flake8_annotations: Option<Flake8AnnotationsOptions>,
@@ -746,6 +748,7 @@ impl LintConfiguration {
             task_tags: options.common.task_tags,
             logger_objects: options.common.logger_objects,
             typing_modules: options.common.typing_modules,
+            typing_extensions: options.typing_extensions,
 
             // Plugins
             flake8_annotations: options.common.flake8_annotations,
@@ -1170,6 +1173,7 @@ impl LintConfiguration {
             pylint: self.pylint.combine(config.pylint),
             pyupgrade: self.pyupgrade.combine(config.pyupgrade),
             ruff: self.ruff.combine(config.ruff),
+            typing_extensions: self.typing_extensions,
         }
     }
 }

crates/ruff_workspace/src/options.rs

@@ -513,6 +513,22 @@ pub struct LintOptions {
         "#
     )]
     pub preview: Option<bool>,
+
+    /// Whether to allow imports from the third-party `typing_extensions` module for Python versions
+    /// before a symbol was added to the first-party `typing` module.
+    ///
+    /// Many rules try to import symbols from the `typing` module but fall back to
+    /// `typing_extensions` for earlier versions of Python. This option can be used to disable this
+    /// fallback behavior in cases where `typing_extensions` is not installed.
+    #[option(
+        default = "true",
+        value_type = "bool",
+        example = r#"
+            # Disable `typing_extensions` imports
+            typing-extensions = false
+        "#
+    )]
+    pub typing_extensions: Option<bool>,
 }
 
 /// Newtype wrapper for [`LintCommonOptions`] that allows customizing the JSON schema and omitting the fields from the [`OptionsMetadata`].
@@ -3876,6 +3892,7 @@ pub struct LintOptionsWire {
     pydoclint: Option<PydoclintOptions>,
     ruff: Option<RuffOptions>,
     preview: Option<bool>,
+    typing_extensions: Option<bool>,
 }
 
 impl From<LintOptionsWire> for LintOptions {
@@ -3930,6 +3947,7 @@ impl From<LintOptionsWire> for LintOptions {
             pydoclint,
             ruff,
             preview,
+            typing_extensions,
         } = value;
 
         LintOptions {
@@ -3985,6 +4003,7 @@ impl From<LintOptionsWire> for LintOptions {
             pydoclint,
             ruff,
             preview,
+            typing_extensions,
         }
     }
 }