Add SortedAttributesRule

fixit/rules/sorted_attributes_rule.py

@@ -0,0 +1,115 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+from typing import List, Union
+
+import libcst as cst
+import libcst.matchers as m
+
+from fixit import CstLintRule, InvalidTestCase as Invalid, ValidTestCase as Valid
+
+
+LineType = Union[cst.BaseSmallStatement, cst.BaseStatement]
+
+
+class SortedAttributesRule(CstLintRule):
+    """
+    Ever wanted to sort a bunch of class attributes alphabetically?
+    Well now it's easy! Just add "@sorted-attributes" in the doc string of
+    a class definition and lint will automatically sort all attributes alphabetically.
+
+    Feel free to add other methods and such -- it should only affect class attributes.
+    """
+
+    INVALID = [
+        Invalid(
+            """
+            class MyUnsortedConstants:
+                \"\"\"
+                @sorted-attributes
+                \"\"\"
+                z = "hehehe"
+                B = 'aaa234'
+                A = 'zzz123'
+                cab = "foo bar"
+                Daaa = "banana"
+
+                @classmethod
+                def get_foo(cls) -> str:
+                    return "some random thing"
+           """,
+            expected_replacement="""
+            class MyUnsortedConstants:
+                \"\"\"
+                @sorted-attributes
+                \"\"\"
+                A = 'zzz123'
+                B = 'aaa234'
+                Daaa = "banana"
+                cab = "foo bar"
+                z = "hehehe"
+
+                @classmethod
+                def get_foo(cls) -> str:
+                    return "some random thing"
+           """,
+        )
+    ]
+    VALID = [
+        Valid(
+            """
+            class MyConstants:
+                \"\"\"
+                @sorted-attributes
+                \"\"\"
+                A = 'zzz123'
+                B = 'aaa234'
+
+            class MyUnsortedConstants:
+                B = 'aaa234'
+                A = 'zzz123'
+           """
+        )
+    ]
+    MESSAGE: str = "It appears you are using the @sorted-attributes directive and the class variables are unsorted. See the lint autofix suggestion."
+
+    def visit_ClassDef(self, node: cst.ClassDef) -> None:
+        doc_string = node.get_docstring()
+        if not doc_string or "@sorted-attributes" not in doc_string:
+            return
+
+        found_any_assign: bool = False
+        pre_assign_lines: List[LineType] = []
+        assign_lines: List[LineType] = []
+        post_assign_lines: List[LineType] = []
+
+        def _add_unmatched_line(line: LineType) -> None:
+            post_assign_lines.append(
+                line
+            ) if found_any_assign else pre_assign_lines.append(line)
+
+        for line in node.body.body:
+            if m.matches(
+                line, m.SimpleStatementLine(body=[m.Assign(targets=[m.AssignTarget()])])
+            ):
+                found_any_assign = True
+                assign_lines.append(line)
+            else:
+                _add_unmatched_line(line)
+                continue
+
+        sorted_assign_lines = sorted(
+            assign_lines, key=lambda line: line.body[0].targets[0].target.value
+        )
+        if sorted_assign_lines == assign_lines:
+            return
+        self.report(
+            node,
+            replacement=node.with_changes(
+                body=node.body.with_changes(
+                    body=pre_assign_lines + sorted_assign_lines + post_assign_lines
+                )
+            ),
+        )