Copy over comments when hugging power ops

CHANGES.md

@@ -10,6 +10,9 @@
 
 <!-- Changes that affect Black's stable style -->
 
+- Comments are no longer deleted when a line had spaces removed around power operators
+  (#2874)
+
 ### Preview style
 
 <!-- Changes that affect Black's preview style -->
@@ -46,6 +49,10 @@
 
 <!-- Changes to the parser or to version autodetection -->
 
+- Type comments are now included in the AST equivalence check consistently so accidental
+  deletion raises an error. Though type comments can't be tracked when running on PyPy
+  3.7 due to standard library limitations. (#2874)
+
 ### Performance
 
 <!-- Changes that improve Black's performance. -->

src/black/parsing.py

@@ -152,14 +152,22 @@ def parse_single_version(
     src: str, version: Tuple[int, int]
 ) -> Union[ast.AST, ast3.AST]:
     filename = "<unknown>"
-    # typed_ast is needed because of feature version limitations in the builtin ast
+    # typed-ast is needed because of feature version limitations in the builtin ast 3.8>
     if sys.version_info >= (3, 8) and version >= (3,):
-        return ast.parse(src, filename, feature_version=version)
-    elif version >= (3,):
-        if _IS_PYPY:
-            return ast3.parse(src, filename)
+        return ast.parse(src, filename, feature_version=version, type_comments=True)
+
+    if _IS_PYPY:
+        # PyPy 3.7 doesn't support type comment tracking which is not ideal, but there's
+        # not much we can do as typed-ast won't work either.
+        if sys.version_info >= (3, 8):
+            return ast3.parse(src, filename, type_comments=True)
         else:
-            return ast3.parse(src, filename, feature_version=version[1])
+            return ast3.parse(src, filename)
+    else:
+        # Typed-ast is guaranteed to be used here and automatically tracks type
+        # comments separately.
+        return ast3.parse(src, filename, feature_version=version[1])
+
     raise AssertionError("INTERNAL ERROR: Tried parsing unsupported Python version!")
 
 

src/black/trans.py

@@ -121,7 +121,7 @@ def is_simple_operand(index: int, kind: Literal["base", "exponent"]) -> bool:
 
         return False
 
-    leaves: List[Leaf] = []
+    new_line = line.clone()
     should_hug = False
     for idx, leaf in enumerate(line.leaves):
         new_leaf = leaf.clone()
@@ -139,18 +139,14 @@ def is_simple_operand(index: int, kind: Literal["base", "exponent"]) -> bool:
         if should_hug:
             new_leaf.prefix = ""
 
-        leaves.append(new_leaf)
-
-    yield Line(
-        mode=line.mode,
-        depth=line.depth,
-        leaves=leaves,
-        comments=line.comments,
-        bracket_tracker=line.bracket_tracker,
-        inside_brackets=line.inside_brackets,
-        should_split_rhs=line.should_split_rhs,
-        magic_trailing_comma=line.magic_trailing_comma,
-    )
+        # We have to be careful to make a new line properly:
+        # - bracket related metadata must be maintained (handled by Line.append)
+        # - comments need to copied over, updating the leaf IDs they're attached to
+        new_line.append(new_leaf, preformatted=True)
+        for comment_leaf in line.comments_after(leaf):
+            new_line.append(comment_leaf, preformatted=True)
+
+    yield new_line
 
 
 class StringTransformer(ABC):

src/blib2to3/pytree.py

@@ -451,7 +451,6 @@ def clone(self) -> "Leaf":
             self.value,
             (self.prefix, (self.lineno, self.column)),
             fixers_applied=self.fixers_applied,
-            opening_bracket=self.opening_bracket,
         )
 
     def leaves(self) -> Iterator["Leaf"]:

tests/data/simple_cases/power_op_spacing.py

@@ -49,6 +49,20 @@ def function_dont_replace_spaces():
 q = [10.5**i for i in range(6)]
 
 
+# WE SHOULD DEFINITELY NOT EAT THESE COMMENTS (https://github.com/psf/black/issues/2873)
+if hasattr(view, "sum_of_weights"):
+    return np.divide(  # type: ignore[no-any-return]
+        view.variance,  # type: ignore[union-attr]
+        view.sum_of_weights,  # type: ignore[union-attr]
+        out=np.full(view.sum_of_weights.shape, np.nan),  # type: ignore[union-attr]
+        where=view.sum_of_weights**2 > view.sum_of_weights_squared,  # type: ignore[union-attr]
+    )
+
+return np.divide(
+    where=view.sum_of_weights_of_weight_long**2 > view.sum_of_weights_squared,  # type: ignore
+)
+
+
 # output
 
 
@@ -101,3 +115,17 @@ def function_dont_replace_spaces():
 o = settings(max_examples=10**6.0)
 p = {(k, k**2): v**2.0 for k, v in pairs}
 q = [10.5**i for i in range(6)]
+
+
+# WE SHOULD DEFINITELY NOT EAT THESE COMMENTS (https://github.com/psf/black/issues/2873)
+if hasattr(view, "sum_of_weights"):
+    return np.divide(  # type: ignore[no-any-return]
+        view.variance,  # type: ignore[union-attr]
+        view.sum_of_weights,  # type: ignore[union-attr]
+        out=np.full(view.sum_of_weights.shape, np.nan),  # type: ignore[union-attr]
+        where=view.sum_of_weights**2 > view.sum_of_weights_squared,  # type: ignore[union-attr]
+    )
+
+return np.divide(
+    where=view.sum_of_weights_of_weight_long**2 > view.sum_of_weights_squared,  # type: ignore
+)