Delimit multiline expressions according to math operator priority

Fixes #148

README.md

@@ -540,6 +540,9 @@ More details can be found in [CONTRIBUTING](CONTRIBUTING.md).
 
 * slices are now formatted according to PEP 8 (#178)
 
+* math operators now use their respective priorities for delimiting multiline
+  expressions (#148)
+
 * empty parentheses in a class definition are now removed (#145, #180)
 
 * fixed an invalid trailing comma sometimes left in imports (#185)

black.py

@@ -553,19 +553,20 @@ def show(cls, code: str) -> None:
     token.GREATEREQUAL,
 }
 MATH_OPERATORS = {
+    token.VBAR,
+    token.CIRCUMFLEX,
+    token.AMPER,
+    token.LEFTSHIFT,
+    token.RIGHTSHIFT,
     token.PLUS,
     token.MINUS,
     token.STAR,
     token.SLASH,
-    token.VBAR,
-    token.AMPER,
-    token.PERCENT,
-    token.CIRCUMFLEX,
-    token.TILDE,
-    token.LEFTSHIFT,
-    token.RIGHTSHIFT,
-    token.DOUBLESTAR,
     token.DOUBLESLASH,
+    token.PERCENT,
+    token.AT,
+    token.TILDE,
+    token.DOUBLESTAR,
 }
 STARS = {token.STAR, token.DOUBLESTAR}
 VARARGS_PARENTS = {
@@ -599,12 +600,27 @@ def show(cls, code: str) -> None:
     syms.power,
 }
 COMPREHENSION_PRIORITY = 20
-COMMA_PRIORITY = 10
-TERNARY_PRIORITY = 7
-LOGIC_PRIORITY = 5
-STRING_PRIORITY = 4
-COMPARATOR_PRIORITY = 3
-MATH_PRIORITY = 1
+COMMA_PRIORITY = 18
+TERNARY_PRIORITY = 16
+LOGIC_PRIORITY = 14
+STRING_PRIORITY = 12
+COMPARATOR_PRIORITY = 10
+MATH_PRIORITIES = {
+    token.VBAR: 8,
+    token.CIRCUMFLEX: 7,
+    token.AMPER: 6,
+    token.LEFTSHIFT: 5,
+    token.RIGHTSHIFT: 5,
+    token.PLUS: 4,
+    token.MINUS: 4,
+    token.STAR: 3,
+    token.SLASH: 3,
+    token.DOUBLESLASH: 3,
+    token.PERCENT: 3,
+    token.AT: 3,
+    token.TILDE: 2,
+    token.DOUBLESTAR: 1,
+}
 
 
 @dataclass
@@ -1649,7 +1665,7 @@ def is_split_before_delimiter(leaf: Leaf, previous: Leaf = None) -> int:
         and leaf.parent
         and leaf.parent.type not in {syms.factor, syms.star_expr}
     ):
-        return MATH_PRIORITY
+        return MATH_PRIORITIES[leaf.type]
 
     if leaf.type in COMPARATORS:
         return COMPARATOR_PRIORITY

tests/expression.diff

@@ -129,7 +129,7 @@
  ]
  slice[0]
  slice[0:1]
-@@ -123,91 +145,119 @@
+@@ -123,103 +145,140 @@
  numpy[-(c + 1) :, d]
  numpy[:, l[-2]]
  numpy[:, ::-1]
@@ -244,6 +244,18 @@
 -if (
 -    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa /
 -    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+-):
+-    return True
+-if (
+-    ~ aaaa.a + aaaa.b - aaaa.c * aaaa.d / aaaa.e | aaaa.f & aaaa.g % aaaa.h ^ aaaa.i << aaaa.k >> aaaa.l ** aaaa.m // aaaa.n
+-):
+-    return True
+-if (
+-    ~ aaaaaaaa.a + aaaaaaaa.b - aaaaaaaa.c @ aaaaaaaa.d / aaaaaaaa.e | aaaaaaaa.f & aaaaaaaa.g % aaaaaaaa.h ^ aaaaaaaa.i << aaaaaaaa.k >> aaaaaaaa.l ** aaaaaaaa.m // aaaaaaaa.n
+-):
+-    return True
+-if (
+-    ~ aaaaaaaaaaaaaaaa.a + aaaaaaaaaaaaaaaa.b - aaaaaaaaaaaaaaaa.c * aaaaaaaaaaaaaaaa.d @ aaaaaaaaaaaaaaaa.e | aaaaaaaaaaaaaaaa.f & aaaaaaaaaaaaaaaa.g % aaaaaaaaaaaaaaaa.h ^ aaaaaaaaaaaaaaaa.i << aaaaaaaaaaaaaaaa.k >> aaaaaaaaaaaaaaaa.l ** aaaaaaaaaaaaaaaa.m // aaaaaaaaaaaaaaaa.n
 +print(*lambda x: x)
 +assert not Test, "Short message"
 +assert (
@@ -296,6 +308,27 @@
 +if (
 +    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 +    / aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
++):
++    return True
++if (
++    ~aaaa.a + aaaa.b - aaaa.c * aaaa.d / aaaa.e
++    | aaaa.f & aaaa.g % aaaa.h ^ aaaa.i << aaaa.k >> aaaa.l ** aaaa.m // aaaa.n
++):
++    return True
++if (
++    ~aaaaaaaa.a + aaaaaaaa.b - aaaaaaaa.c @ aaaaaaaa.d / aaaaaaaa.e
++    | aaaaaaaa.f & aaaaaaaa.g % aaaaaaaa.h
++    ^ aaaaaaaa.i << aaaaaaaa.k >> aaaaaaaa.l ** aaaaaaaa.m // aaaaaaaa.n
++):
++    return True
++if (
++    ~aaaaaaaaaaaaaaaa.a
++    + aaaaaaaaaaaaaaaa.b
++    - aaaaaaaaaaaaaaaa.c * aaaaaaaaaaaaaaaa.d @ aaaaaaaaaaaaaaaa.e
++    | aaaaaaaaaaaaaaaa.f & aaaaaaaaaaaaaaaa.g % aaaaaaaaaaaaaaaa.h
++    ^ aaaaaaaaaaaaaaaa.i
++    << aaaaaaaaaaaaaaaa.k
++    >> aaaaaaaaaaaaaaaa.l ** aaaaaaaaaaaaaaaa.m // aaaaaaaaaaaaaaaa.n
  ):
      return True
  last_call()

tests/expression.py

@@ -208,6 +208,18 @@ async def f():
     aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 ):
     return True
+if (
+    ~ aaaa.a + aaaa.b - aaaa.c * aaaa.d / aaaa.e | aaaa.f & aaaa.g % aaaa.h ^ aaaa.i << aaaa.k >> aaaa.l ** aaaa.m // aaaa.n
+):
+    return True
+if (
+    ~ aaaaaaaa.a + aaaaaaaa.b - aaaaaaaa.c @ aaaaaaaa.d / aaaaaaaa.e | aaaaaaaa.f & aaaaaaaa.g % aaaaaaaa.h ^ aaaaaaaa.i << aaaaaaaa.k >> aaaaaaaa.l ** aaaaaaaa.m // aaaaaaaa.n
+):
+    return True
+if (
+    ~ aaaaaaaaaaaaaaaa.a + aaaaaaaaaaaaaaaa.b - aaaaaaaaaaaaaaaa.c * aaaaaaaaaaaaaaaa.d @ aaaaaaaaaaaaaaaa.e | aaaaaaaaaaaaaaaa.f & aaaaaaaaaaaaaaaa.g % aaaaaaaaaaaaaaaa.h ^ aaaaaaaaaaaaaaaa.i << aaaaaaaaaaaaaaaa.k >> aaaaaaaaaaaaaaaa.l ** aaaaaaaaaaaaaaaa.m // aaaaaaaaaaaaaaaa.n
+):
+    return True
 last_call()
 # standalone comment at ENDMARKER
 
@@ -475,5 +487,26 @@ async def f():
     / aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 ):
     return True
+if (
+    ~aaaa.a + aaaa.b - aaaa.c * aaaa.d / aaaa.e
+    | aaaa.f & aaaa.g % aaaa.h ^ aaaa.i << aaaa.k >> aaaa.l ** aaaa.m // aaaa.n
+):
+    return True
+if (
+    ~aaaaaaaa.a + aaaaaaaa.b - aaaaaaaa.c @ aaaaaaaa.d / aaaaaaaa.e
+    | aaaaaaaa.f & aaaaaaaa.g % aaaaaaaa.h
+    ^ aaaaaaaa.i << aaaaaaaa.k >> aaaaaaaa.l ** aaaaaaaa.m // aaaaaaaa.n
+):
+    return True
+if (
+    ~aaaaaaaaaaaaaaaa.a
+    + aaaaaaaaaaaaaaaa.b
+    - aaaaaaaaaaaaaaaa.c * aaaaaaaaaaaaaaaa.d @ aaaaaaaaaaaaaaaa.e
+    | aaaaaaaaaaaaaaaa.f & aaaaaaaaaaaaaaaa.g % aaaaaaaaaaaaaaaa.h
+    ^ aaaaaaaaaaaaaaaa.i
+    << aaaaaaaaaaaaaaaa.k
+    >> aaaaaaaaaaaaaaaa.l ** aaaaaaaaaaaaaaaa.m // aaaaaaaaaaaaaaaa.n
+):
+    return True
 last_call()
 # standalone comment at ENDMARKER