Fix long lines with power operator(s) getting splitted before line length (#3942)

Fixes #3889

Author: henriholopainen

CHANGES.md

@@ -16,6 +16,7 @@
 
 <!-- Changes that affect Black's preview style -->
 
+- Fix long lines with power operators getting splitted before the line length (#3942)
 - Long type hints are now wrapped in parentheses and properly indented when split across
   multiple lines (#3899)
 - Magic trailing commas are now respected in return types. (#3916)

src/black/linegen.py

@@ -536,6 +536,17 @@ def __post_init__(self) -> None:
         self.visit_case_block = self.visit_match_case
 
 
+def _hugging_power_ops_line_to_string(
+    line: Line,
+    features: Collection[Feature],
+    mode: Mode,
+) -> Optional[str]:
+    try:
+        return line_to_string(next(hug_power_op(line, features, mode)))
+    except CannotTransform:
+        return None
+
+
 def transform_line(
     line: Line, mode: Mode, features: Collection[Feature] = ()
 ) -> Iterator[Line]:
@@ -551,6 +562,14 @@ def transform_line(
 
     line_str = line_to_string(line)
 
+    # We need the line string when power operators are hugging to determine if we should
+    # split the line. Default to line_str, if no power operator are present on the line.
+    line_str_hugging_power_ops = (
+        (_hugging_power_ops_line_to_string(line, features, mode) or line_str)
+        if Preview.fix_power_op_line_length in mode
+        else line_str
+    )
+
     ll = mode.line_length
     sn = mode.string_normalization
     string_merge = StringMerger(ll, sn)
@@ -564,7 +583,7 @@ def transform_line(
         and not line.should_split_rhs
         and not line.magic_trailing_comma
         and (
-            is_line_short_enough(line, mode=mode, line_str=line_str)
+            is_line_short_enough(line, mode=mode, line_str=line_str_hugging_power_ops)
             or line.contains_unsplittable_type_ignore()
         )
         and not (line.inside_brackets and line.contains_standalone_comments())

src/black/mode.py

@@ -188,6 +188,7 @@ class Preview(Enum):
     dummy_implementations = auto()
     walrus_subscript = auto()
     module_docstring_newlines = auto()
+    fix_power_op_line_length = auto()
 
 
 class Deprecated(UserWarning):

tests/data/cases/power_op_spacing.py

@@ -29,6 +29,13 @@ def function_dont_replace_spaces():
 p = {(k, k**2): v**2 for k, v in pairs}
 q = [10**i for i in range(6)]
 r = x**y
+s = 1 ** 1
+t = (
+    1
+    ** 1
+    **1
+    ** 1
+)
 
 a = 5.0**~4.0
 b = 5.0 ** f()
@@ -47,6 +54,13 @@ 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)]
+s = 1.0 ** 1.0
+t = (
+    1.0
+    ** 1.0
+    **1.0
+    ** 1.0
+)
 
 
 # WE SHOULD DEFINITELY NOT EAT THESE COMMENTS (https://github.com/psf/black/issues/2873)
@@ -97,6 +111,8 @@ def function_dont_replace_spaces():
 p = {(k, k**2): v**2 for k, v in pairs}
 q = [10**i for i in range(6)]
 r = x**y
+s = 1**1
+t = 1**1**1**1
 
 a = 5.0**~4.0
 b = 5.0 ** f()
@@ -115,6 +131,8 @@ 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)]
+s = 1.0**1.0
+t = 1.0**1.0**1.0**1.0
 
 
 # WE SHOULD DEFINITELY NOT EAT THESE COMMENTS (https://github.com/psf/black/issues/2873)

tests/data/cases/preview_power_op_spacing.py

@@ -0,0 +1,97 @@
+# flags: --preview
+a = 1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1
+b = 1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1
+c = 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1 ** 1
+d = 1**1 ** 1**1 ** 1**1 ** 1**1 ** 1**1**1 ** 1 ** 1**1 ** 1**1**1**1**1 ** 1 ** 1**1**1 **1**1** 1 ** 1 ** 1
+e = 𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟
+f = 𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟
+
+a = 1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0
+b = 1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0
+c = 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0 ** 1.0
+d = 1.0**1.0 ** 1.0**1.0 ** 1.0**1.0 ** 1.0**1.0 ** 1.0**1.0**1.0 ** 1.0 ** 1.0**1.0 ** 1.0**1.0**1.0
+
+# output
+a = 1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1
+b = (
+    1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+    ** 1
+)
+c = 1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1
+d = 1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1**1
+e = 𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟**𨉟
+f = (
+    𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+    ** 𨉟
+)
+
+a = 1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0
+b = (
+    1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+    ** 1.0
+)
+c = 1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0
+d = 1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0**1.0