[flake8-import-conventions] Improve syntax check for aliases suppli…

…ed in configuration for `unconventional-import-alias (ICN001)` (#14745)

This PR improves on #14477 by:

- Ensuring user's do not require the module alias "__debug__", which is unassignable
- Validating the linter settings for
`lint.flake8-import-conventions.extend-aliases` (whereas previously we
only did this for `lint.flake8-import-conventions.aliases`).

Closes #14662

crates/ruff/tests/lint.rs

@@ -2003,6 +2003,42 @@ fn flake8_import_convention_invalid_aliases_config_alias_name() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn flake8_import_convention_invalid_aliases_config_extend_alias_name() -> Result<()> {
+    let tempdir = TempDir::new()?;
+    let ruff_toml = tempdir.path().join("ruff.toml");
+    fs::write(
+        &ruff_toml,
+        r#"
+[lint.flake8-import-conventions.extend-aliases]
+"module.name" = "__debug__"
+"#,
+    )?;
+
+    insta::with_settings!({
+        filters => vec![(tempdir_filter(&tempdir).as_str(), "[TMP]/")]
+    }, {
+        assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
+            .args(STDIN_BASE_OPTIONS)
+            .arg("--config")
+            .arg(&ruff_toml)
+    , @r###"
+        success: false
+        exit_code: 2
+        ----- stdout -----
+
+        ----- stderr -----
+        ruff failed
+          Cause: Failed to parse [TMP]/ruff.toml
+          Cause: TOML parse error at line 2, column 2
+          |
+        2 | [lint.flake8-import-conventions.extend-aliases]
+          |  ^^^^
+        invalid value: string "__debug__", expected an assignable Python identifier
+        "###);});
+    Ok(())
+}
+
 #[test]
 fn flake8_import_convention_invalid_aliases_config_module_name() -> Result<()> {
     let tempdir = TempDir::new()?;

crates/ruff_workspace/src/options.rs

@@ -1342,7 +1342,7 @@ pub struct Flake8ImportConventionsOptions {
             "dask.dataframe" = "dd"
         "#
     )]
-    pub extend_aliases: Option<FxHashMap<String, String>>,
+    pub extend_aliases: Option<FxHashMap<ModuleName, Alias>>,
 
     /// A mapping from module to its banned import aliases.
     #[option(
@@ -1415,6 +1415,15 @@ impl<'de> Deserialize<'de> for Alias {
         D: Deserializer<'de>,
     {
         let name = String::deserialize(deserializer)?;
+        // Assigning to "__debug__" is a SyntaxError
+        // see the note here:
+        // https://docs.python.org/3/library/constants.html#debug__
+        if &*name == "__debug__" {
+            return Err(de::Error::invalid_value(
+                de::Unexpected::Str(&name),
+                &"an assignable Python identifier",
+            ));
+        }
         if is_identifier(&name) {
             Ok(Self(name))
         } else {
@@ -1436,7 +1445,11 @@ impl Flake8ImportConventionsOptions {
             None => flake8_import_conventions::settings::default_aliases(),
         };
         if let Some(extend_aliases) = self.extend_aliases {
-            aliases.extend(extend_aliases);
+            aliases.extend(
+                extend_aliases
+                    .into_iter()
+                    .map(|(module, alias)| (module.into_string(), alias.into_string())),
+            );
         }
 
         flake8_import_conventions::settings::Settings {