Support lint ignore directives in more places

Adds logic to `LintRule.node_comments()` looking for directives in more
locations relative to the current node:

- trailing inline comments after commas
- preceding and trailing comments inside brackets
- preceding comments before/after decorators for classes and functions

In addition, to better support suppressions for decorators themselves,
the logic to break upward searching until reaching a `leading_lines`
node has been modified to exclude `Decorator` nodes which have their own
leading lines that aren't used for the first decorator on a class.

Based on code examples reported in #413

ghstack-source-id: 4907870d9ecde15fd1110b3d276bc7f95569c513
Pull Request resolved: #441

src/fixit/rule.py

@@ -22,10 +22,14 @@
 from libcst import (
     BaseSuite,
     BatchableCSTVisitor,
+    Comma,
     CSTNode,
+    Decorator,
     EmptyLine,
     IndentedBlock,
+    LeftSquareBracket,
     Module,
+    RightSquareBracket,
     SimpleStatementSuite,
     TrailingWhitespace,
 )
@@ -134,14 +138,42 @@ def node_comments(self, node: CSTNode) -> Generator[str, None, None]:
             if tw and tw.comment:
                 yield tw.comment.value
 
+            comma: Optional[Comma] = getattr(node, "comma", None)
+            if isinstance(comma, Comma):
+                tw = getattr(comma.whitespace_after, "first_line", None)
+                if tw and tw.comment:
+                    yield tw.comment.value
+
+            rb: Optional[RightSquareBracket] = getattr(node, "rbracket", None)
+            if rb is not None:
+                tw = getattr(rb.whitespace_before, "first_line", None)
+                if tw and tw.comment:
+                    yield tw.comment.value
+
+            el: Optional[Sequence[EmptyLine]] = None
+            lb: Optional[LeftSquareBracket] = getattr(node, "lbracket", None)
+            if lb is not None:
+                el = getattr(lb.whitespace_after, "empty_lines", None)
+                if el is not None:
+                    for line in el:
+                        if line.comment:
+                            yield line.comment.value
+
+            el = getattr(node, "lines_after_decorators", None)
+            if el is not None:
+                for line in el:
+                    if line.comment:
+                        yield line.comment.value
+
             ll: Optional[Sequence[EmptyLine]] = getattr(node, "leading_lines", None)
             if ll is not None:
                 for line in ll:
                     if line.comment:
                         yield line.comment.value
-                # stop looking once we've gone up far enough for leading_lines,
-                # even if there are no comment lines here at all
-                break
+                if not isinstance(node, Decorator):
+                    # stop looking once we've gone up far enough for leading_lines,
+                    # even if there are no comment lines here at all
+                    break
 
             node = self.get_metadata(ParentNodeProvider, node)
 

src/fixit/tests/rule.py

@@ -282,7 +282,7 @@ class Foo(object):
         ):
             idx += 1
             content = dedent(code).encode("utf-8")
-            with self.subTest(f"test case {idx}"):
+            with self.subTest(f"test ignore {idx}"):
                 runner = LintRunner(Path("fake.py"), content)
                 violations = list(
                     runner.collect_violations([ExerciseReportRule()], Config())