black/parser: partial support for pattern matching (#2586)

[etc/vim.git] / src / black / linegen.py

diff --git a/src/black/linegen.py b/src/black/linegen.py
index fafaf1032ca55e002d49a5c3b7a8789f57f522e4..8cf32c973bb6a4880e543ec6a51ec06ff54dc492 100644 (file)
--- a/src/black/linegen.py
+++ b/src/black/linegen.py
@@ -126,7 +126,7 @@ class LineGenerator(Visitor[Line]):
         """Visit a statement.
 
         This implementation is shared for `if`, `while`, `for`, `try`, `except`,
-        `def`, `with`, `class`, `assert` and assignments.
+        `def`, `with`, `class`, `assert`, `match`, `case` and assignments.
 
         The relevant Python language `keywords` for a given statement will be
         NAME leaves within it. This methods puts those on a separate line.
@@ -292,6 +292,10 @@ class LineGenerator(Visitor[Line]):
         self.visit_async_funcdef = self.visit_async_stmt
         self.visit_decorated = self.visit_decorators
 
+        # PEP 634
+        self.visit_match_stmt = partial(v, keywords={"match"}, parens=Ø)
+        self.visit_case_block = partial(v, keywords={"case"}, parens=Ø)
+
 
 def transform_line(
     line: Line, mode: Mode, features: Collection[Feature] = ()
@@ -503,14 +507,14 @@ def right_hand_split(
             yield from right_hand_split(line, line_length, features=features, omit=omit)
             return
 
-        except CannotSplit:
+        except CannotSplit as e:
             if not (
                 can_be_split(body)
                 or is_line_short_enough(body, line_length=line_length)
             ):
                 raise CannotSplit(
                     "Splitting failed, body is still too long and can't be split."
-                )
+                ) from e
 
             elif head.contains_multiline_strings() or tail.contains_multiline_strings():
                 raise CannotSplit(
@@ -518,7 +522,7 @@ def right_hand_split(
                     " satisfy the splitting algorithm because the head or the tail"
                     " contains multiline strings which by definition never fit one"
                     " line."
-                )
+                ) from e
 
     ensure_visible(opening_bracket)
     ensure_visible(closing_bracket)
@@ -635,13 +639,13 @@ def delimiter_split(line: Line, features: Collection[Feature] = ()) -> Iterator[
     try:
         last_leaf = line.leaves[-1]
     except IndexError:
-        raise CannotSplit("Line empty")
+        raise CannotSplit("Line empty") from None
 
     bt = line.bracket_tracker
     try:
         delimiter_priority = bt.max_delimiter_priority(exclude={id(last_leaf)})
     except ValueError:
-        raise CannotSplit("No delimiters found")
+        raise CannotSplit("No delimiters found") from None
 
     if delimiter_priority == DOT_PRIORITY:
         if bt.delimiter_count_with_priority(delimiter_priority) == 1: