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Remove unnecessary parentheses from with statements #2926

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Apr 3, 2022
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1a499b2
Remove unnecessary parentheses from WITH statements
jpy-git Mar 15, 2022
1a2c13b
Add unit tests
jpy-git Mar 15, 2022
27a4bfd
Move functionality to preview mode
jpy-git Mar 15, 2022
ddc1a3f
Merge branch 'main' into with_parens
jpy-git Mar 16, 2022
240a6f8
Make logic more DRY
jpy-git Mar 16, 2022
cd0695d
Use or instead of and
jpy-git Mar 16, 2022
0e0d9f8
Make unit test py>=3.9
jpy-git Mar 17, 2022
3c14ab2
re-add preview style comment in CHANGES.md
jpy-git Mar 18, 2022
254fc91
Merge branch 'main' into with_parens
jpy-git Mar 21, 2022
d5db697
Update for latest master
jpy-git Mar 21, 2022
87aa74d
make redundant parens enum entry consistent
jpy-git Mar 21, 2022
aaa902a
add brackets for clarity
jpy-git Mar 23, 2022
9b62d0e
Merge branch 'main' into with_parens
JelleZijlstra Mar 24, 2022
68bb6d8
Merge branch 'main' into with_parens
JelleZijlstra Mar 24, 2022
3f8db3d
Fix condition after merge
jpy-git Mar 24, 2022
ac698f8
One-pass fix for removing brackets in for/with
jpy-git Mar 25, 2022
6532485
Merge branch 'main' into with_parens
JelleZijlstra Mar 26, 2022
e61783a
fix parent in as_expr logic
jpy-git Mar 26, 2022
639a2e4
Merge branch 'main' into with_parens
JelleZijlstra Mar 26, 2022
afcb8be
Merge branch 'main' into with_parens
JelleZijlstra Mar 30, 2022
1540bfa
Add deeply nested with bracket examples
jpy-git Apr 2, 2022
0f0a01a
Add deeply nested for bracket examples
jpy-git Apr 2, 2022
bd7373c
Merge branch 'main' into with_parens
jpy-git Apr 2, 2022
99167c2
Moar code comments 'cause ASTs are no joke
ichard26 Apr 2, 2022
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2 changes: 2 additions & 0 deletions CHANGES.md
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,8 @@

<!-- Changes that affect Black's preview style -->

- Remove unnecessary parentheses from `with` statements (#2926)

### _Blackd_

<!-- Changes to blackd -->
Expand Down
82 changes: 63 additions & 19 deletions src/black/linegen.py
Original file line number Diff line number Diff line change
Expand Up @@ -322,9 +322,10 @@ def __post_init__(self) -> None:
self.visit_except_clause = partial(
v, keywords={"except"}, parens={"except"}
)
self.visit_with_stmt = partial(v, keywords={"with"}, parens={"with"})
else:
self.visit_except_clause = partial(v, keywords={"except"}, parens=Ø)
self.visit_with_stmt = partial(v, keywords={"with"}, parens=Ø)
self.visit_with_stmt = partial(v, keywords={"with"}, parens=Ø)
self.visit_funcdef = partial(v, keywords={"def"}, parens=Ø)
self.visit_classdef = partial(v, keywords={"class"}, parens=Ø)
self.visit_expr_stmt = partial(v, keywords=Ø, parens=ASSIGNMENTS)
Expand Down Expand Up @@ -845,11 +846,26 @@ def normalize_invisible_parens(
check_lpar = True

if check_lpar:
if child.type == syms.atom:
if (
preview
and child.type == syms.atom
and node.type == syms.for_stmt
and isinstance(child.prev_sibling, Leaf)
and child.prev_sibling.type == token.NAME
and child.prev_sibling.value == "for"
):
if maybe_make_parens_invisible_in_atom(
child,
parent=node,
remove_brackets_around_comma=True,
):
wrap_in_parentheses(node, child, visible=False)
Comment on lines +849 to +862
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for fix is now very simple. Detect the parent is a for loop and then remove the brackets using the option to remove around commas as well.

elif preview and isinstance(child, Node) and node.type == syms.with_stmt:
remove_with_parens(child, node)
elif child.type == syms.atom:
if maybe_make_parens_invisible_in_atom(
child,
parent=node,
preview=preview,
):
wrap_in_parentheses(node, child, visible=False)
elif is_one_tuple(child):
Expand All @@ -871,38 +887,62 @@ def normalize_invisible_parens(
elif not (isinstance(child, Leaf) and is_multiline_string(child)):
wrap_in_parentheses(node, child, visible=False)

check_lpar = isinstance(child, Leaf) and child.value in parens_after
comma_check = child.type == token.COMMA if preview else False

check_lpar = isinstance(child, Leaf) and (
child.value in parens_after or comma_check
)


def remove_with_parens(node: Node, parent: Node) -> None:
"""Recursively hide optional parens in `with` statements."""
if node.type == syms.atom:
if maybe_make_parens_invisible_in_atom(
node,
parent=parent,
remove_brackets_around_comma=True,
):
wrap_in_parentheses(parent, node, visible=False)
if isinstance(node.children[1], Node):
remove_with_parens(node.children[1], node)
elif node.type == syms.testlist_gexp:
for child in node.children:
if isinstance(child, Node):
remove_with_parens(child, node)
elif node.type == syms.asexpr_test and not any(
leaf.type == token.COLONEQUAL for leaf in node.leaves()
):
if maybe_make_parens_invisible_in_atom(
node.children[0],
parent=node,
remove_brackets_around_comma=True,
):
wrap_in_parentheses(node, node.children[0], visible=False)


def maybe_make_parens_invisible_in_atom(
node: LN,
parent: LN,
preview: bool = False,
remove_brackets_around_comma: bool = False,
) -> bool:
"""If it's safe, make the parens in the atom `node` invisible, recursively.
Additionally, remove repeated, adjacent invisible parens from the atom `node`
as they are redundant.

Returns whether the node should itself be wrapped in invisible parentheses.

"""
if (
preview
and parent.type == syms.for_stmt
and isinstance(node.prev_sibling, Leaf)
and node.prev_sibling.type == token.NAME
and node.prev_sibling.value == "for"
):
for_stmt_check = False
else:
for_stmt_check = True

if (
node.type != syms.atom
or is_empty_tuple(node)
or is_one_tuple(node)
or (is_yield(node) and parent.type != syms.expr_stmt)
or (max_delimiter_priority_in_atom(node) >= COMMA_PRIORITY and for_stmt_check)
or (
# This condition tries to prevent removing non-optional brackets
# around a tuple, however, can be a bit overzealous so we provide
# and option to skip this check for `for` and `with` statements.
not remove_brackets_around_comma
and max_delimiter_priority_in_atom(node) >= COMMA_PRIORITY
)
Comment on lines +955 to +961
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So the reason I had the for_stmt_check/with_stmt_check initially was to disable this check for the reason in the above comment (basically it's hard to cleanly detect a tuple).

The issue was that nested brackets are nested atoms so when we recursed into the second level of this function the parent would no longer be for_stmt or with_stmt so my check would fail and require a second run. I've added an argument to disable this check and then we can just use this when we're removing brackets from for/with in the main loop.

):
return False

Expand All @@ -925,7 +965,11 @@ def maybe_make_parens_invisible_in_atom(
# make parentheses invisible
first.value = ""
last.value = ""
maybe_make_parens_invisible_in_atom(middle, parent=parent, preview=preview)
maybe_make_parens_invisible_in_atom(
middle,
parent=parent,
remove_brackets_around_comma=remove_brackets_around_comma,
)

if is_atom_with_invisible_parens(middle):
# Strip the invisible parens from `middle` by replacing
Expand Down
79 changes: 79 additions & 0 deletions tests/data/remove_with_brackets.py
Original file line number Diff line number Diff line change
@@ -0,0 +1,79 @@
with (open("bla.txt")):
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pass

with (open("bla.txt")), (open("bla.txt")):
pass

with (open("bla.txt") as f):
pass

# Remove brackets within alias expression
with (open("bla.txt")) as f:
pass

# Remove brackets around one-line context managers
with (open("bla.txt") as f, (open("x"))):
pass

with ((open("bla.txt")) as f, open("x")):
pass

with (CtxManager1() as example1, CtxManager2() as example2):
...

# Brackets remain when using magic comma
with (CtxManager1() as example1, CtxManager2() as example2,):
...

# Brackets remain for multi-line context managers
with (CtxManager1() as example1, CtxManager2() as example2, CtxManager2() as example2, CtxManager2() as example2, CtxManager2() as example2):
...

# Don't touch assignment expressions
with (y := open("./test.py")) as f:
pass

# output
with open("bla.txt"):
pass

with open("bla.txt"), open("bla.txt"):
pass

with open("bla.txt") as f:
pass

# Remove brackets within alias expression
with open("bla.txt") as f:
pass

# Remove brackets around one-line context managers
with open("bla.txt") as f, open("x"):
pass

with open("bla.txt") as f, open("x"):
pass

with CtxManager1() as example1, CtxManager2() as example2:
...

# Brackets remain when using magic comma
with (
CtxManager1() as example1,
CtxManager2() as example2,
):
...

# Brackets remain for multi-line context managers
with (
CtxManager1() as example1,
CtxManager2() as example2,
CtxManager2() as example2,
CtxManager2() as example2,
CtxManager2() as example2,
):
...

# Don't touch assignment expressions
with (y := open("./test.py")) as f:
pass
10 changes: 10 additions & 0 deletions tests/test_format.py
Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,16 @@ def test_pep_570() -> None:
assert_format(source, expected, minimum_version=(3, 8))


def test_remove_with_brackets() -> None:
source, expected = read_data("remove_with_brackets")
assert_format(
source,
expected,
black.Mode(preview=True),
minimum_version=(3, 9),
)


@pytest.mark.parametrize("filename", PY310_CASES)
def test_python_310(filename: str) -> None:
source, expected = read_data(filename)
Expand Down