Do not sort OrderedDict keyword arguments

CHANGES.rst

@@ -17,6 +17,11 @@ codesorter follows `semantic versioning <https://semver.org/>`_.
   raised ``NameError`` at import. The runtime references reachable through a called
   class or function (transitively) are now treated as dependencies of the calling
   assignment.
+- Do not sort the keyword arguments of an ``OrderedDict`` call. ``OrderedDict(b=2,
+  a=1)`` iterates in argument order and is a distinct value from ``OrderedDict(a=1,
+  b=2)``, so reordering its keyword arguments changed the resulting object. Calls to
+  ``OrderedDict`` (bare or dotted, such as ``collections.OrderedDict``) are now left
+  untouched.
 
 ********************
  0.2.7 (2026/06/15)

README.rst

@@ -24,7 +24,8 @@ CodeSorter is a LibCST codemod that automatically sorts and organizes Python cod
 - **Constant Grouping**: Orders each scope as constants, then classes, then functions,
   sorting constants by dependency while preserving enum and dataclass field order
 - **Keyword Sorting**: Alphabetizes keyword arguments in calls, keyword-only parameters,
-  and dict string keys, while preserving ``*``/``**`` unpacking semantics
+  and dict string keys, while preserving ``*``/``**`` unpacking semantics and the
+  keyword-argument order of order-sensitive callables such as ``OrderedDict``
 - **Pytest Integration**: Special handling for pytest fixtures with proper scope
   ordering
 - **CLI Interface**: Simple command-line interface for easy integration

codesorter/const.py

@@ -34,6 +34,10 @@
     "NamedTuple",
     "TypedDict",
 })
+# Callables whose keyword-argument order is semantically significant, so their calls must
+# not have keyword arguments reordered. ``OrderedDict(a=1, b=2)`` iterates in argument order,
+# and ``OrderedDict(b=2, a=1)`` is a distinct (unequal) value, so the order must be preserved.
+ORDER_SENSITIVE_CALLS: frozenset[str] = frozenset({"OrderedDict"})
 ORDER_SENSITIVE_DECORATORS: frozenset[str] = frozenset({"dataclass", "define", "frozen", "mutable", "attrs"})
 PLAIN_DECORATOR_PARTS = 1
 

codesorter/sort_code.py

@@ -16,6 +16,7 @@
 
 from codesorter.const import (
     ORDER_SENSITIVE_BASES,
+    ORDER_SENSITIVE_CALLS,
     ORDER_SENSITIVE_DECORATORS,
     PLAIN_DECORATOR_PARTS,
     PROPERTY_DECORATOR_PARTS,
@@ -69,6 +70,22 @@ class KeywordArgumentSorter(cst.CSTTransformer):
 
     """
 
+    @staticmethod
+    def _called_name(func: cst.BaseExpression) -> str | None:
+        """Return the trailing name of a call target, or ``None`` if it is not a name.
+
+        Resolves both a bare ``OrderedDict`` (``Name``) and a dotted
+        ``collections.OrderedDict`` (``Attribute``) to ``"OrderedDict"``. An import
+        alias is not followed, matching the suffix-based name matching used elsewhere
+        for order-sensitive classes.
+
+        """
+        if isinstance(func, cst.Attribute):
+            return func.attr.value
+        if isinstance(func, cst.Name):
+            return func.value
+        return None
+
     @staticmethod
     def _sort_comma_runs(
         elements: Sequence[_CommaT],
@@ -107,9 +124,13 @@ def leave_Call(self, original_node: cst.Call, updated_node: cst.Call) -> cst.Cal
         barriers: a call raises ``TypeError`` on any duplicate keyword regardless of
         order, so moving keyword arguments across a ``**`` cannot change the result.
         Positional arguments and ``*`` unpackings stay put because their order
-        determines positional binding.
+        determines positional binding. Calls to an order-sensitive callable such as
+        ``OrderedDict`` are left untouched, since their keyword-argument order is the
+        iteration order and reordering it would change the resulting value.
 
         """
+        if self._called_name(updated_node.func) in ORDER_SENSITIVE_CALLS:
+            return updated_node
         return updated_node.with_changes(
             args=self._sort_comma_runs(
                 updated_node.args,

tests/test_files/order_sensitive_calls_input.py

@@ -0,0 +1,13 @@
+"""OrderedDict keeps its keyword-argument order; other calls and dict literals are sorted."""
+
+import collections
+from collections import OrderedDict
+
+
+def build():
+    """OrderedDict argument order is preserved; the regular call and dict literal are sorted."""
+    ordered = OrderedDict(zeta=1, alpha=2, mu=3)
+    qualified = collections.OrderedDict(zeta=1, alpha=2)
+    regular = submit(zeta=1, alpha=2)
+    literal = {"zeta": 1, "alpha": 2}
+    return literal, ordered, qualified, regular

tests/test_files/order_sensitive_calls_output.py

@@ -0,0 +1,13 @@
+"""OrderedDict keeps its keyword-argument order; other calls and dict literals are sorted."""
+
+import collections
+from collections import OrderedDict
+
+
+def build():
+    """OrderedDict argument order is preserved; the regular call and dict literal are sorted."""
+    ordered = OrderedDict(zeta=1, alpha=2, mu=3)
+    qualified = collections.OrderedDict(zeta=1, alpha=2)
+    regular = submit(alpha=2, zeta=1)
+    literal = {"alpha": 2, "zeta": 1}
+    return literal, ordered, qualified, regular

tests/test_sort_code.py

@@ -309,6 +309,15 @@ def test_order_sensitive(self, test_files):
 
         assert expected_code == result.code
 
+    def test_order_sensitive_calls(self, test_files):
+        """Test that OrderedDict keeps its keyword-argument order while other calls are sorted."""
+        input_code, expected_code = test_files
+        context = CodemodContext()
+        command = SortCodeCommand(context)
+        result = command.transform_module(cst.parse_module(input_code))
+
+        assert expected_code == result.code
+
     def test_property(self, test_files):
         """Test that properties are sorted correctly."""
         input_code, expected_code = test_files