[pep8-naming] Don't flag from imports following conventional import names (N817) (#12946)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

crates/ruff_linter/resources/test/fixtures/pep8_naming/N817.py

@@ -4,3 +4,7 @@ from mod import CamelCase as CC
 
 # OK depending on configured import convention
 import xml.etree.ElementTree as ET
+from xml.etree import ElementTree as ET
+
+# Always an error (relative import)
+from ..xml.eltree import ElementTree as ET

crates/ruff_linter/src/rules/pep8_naming/rules/camelcase_imported_as_acronym.rs

@@ -74,14 +74,7 @@ pub(crate) fn camelcase_imported_as_acronym(
         }
 
         // Ignore names that follow a community-agreed import convention.
-        if checker
-            .settings
-            .flake8_import_conventions
-            .aliases
-            .get(&*alias.name)
-            .map(String::as_str)
-            == Some(asname)
-        {
+        if is_ignored_because_of_import_convention(asname, stmt, alias, checker) {
             return None;
         }
 
@@ -97,3 +90,34 @@ pub(crate) fn camelcase_imported_as_acronym(
     }
     None
 }
+
+fn is_ignored_because_of_import_convention(
+    asname: &str,
+    stmt: &Stmt,
+    alias: &Alias,
+    checker: &Checker,
+) -> bool {
+    let full_name = if let Some(import_from) = stmt.as_import_from_stmt() {
+        // Never test relative imports for exclusion because we can't resolve the full-module name.
+        let Some(module) = import_from.module.as_ref() else {
+            return false;
+        };
+
+        if import_from.level != 0 {
+            return false;
+        }
+
+        std::borrow::Cow::Owned(format!("{module}.{}", alias.name))
+    } else {
+        std::borrow::Cow::Borrowed(&*alias.name)
+    };
+
+    // Ignore names that follow a community-agreed import convention.
+    checker
+        .settings
+        .flake8_import_conventions
+        .aliases
+        .get(&*full_name)
+        .map(String::as_str)
+        == Some(asname)
+}

crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__N817_N817.py.snap

@@ -15,4 +15,9 @@ N817.py:2:17: N817 CamelCase `CamelCase` imported as acronym `CC`
   |                 ^^^^^^^^^^^^^^^ N817
   |
 
-
+N817.py:10:26: N817 CamelCase `ElementTree` imported as acronym `ET`
+   |
+ 9 | # Always an error (relative import)
+10 | from ..xml.eltree import ElementTree as ET
+   |                          ^^^^^^^^^^^^^^^^^ N817
+   |

crates/ruff_linter/src/rules/pep8_naming/snapshots/ruff_linter__rules__pep8_naming__tests__camelcase_imported_as_incorrect_convention.snap

@@ -20,4 +20,22 @@ N817.py:6:8: N817 CamelCase `ElementTree` imported as acronym `ET`
 5 | # OK depending on configured import convention
 6 | import xml.etree.ElementTree as ET
   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ N817
+7 | from xml.etree import ElementTree as ET
   |
+
+N817.py:7:23: N817 CamelCase `ElementTree` imported as acronym `ET`
+  |
+5 | # OK depending on configured import convention
+6 | import xml.etree.ElementTree as ET
+7 | from xml.etree import ElementTree as ET
+  |                       ^^^^^^^^^^^^^^^^^ N817
+8 | 
+9 | # Always an error (relative import)
+  |
+
+N817.py:10:26: N817 CamelCase `ElementTree` imported as acronym `ET`
+   |
+ 9 | # Always an error (relative import)
+10 | from ..xml.eltree import ElementTree as ET
+   |                          ^^^^^^^^^^^^^^^^^ N817
+   |