Surface links to Stability Policy (GH-2848)

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

diff --git a/src/black/trans.py b/src/black/trans.py
index a4d1e6fbc7990f3813dfcc469a906af519252eb7..74d052fe2dcbd0854d11bee16417777e28ed26eb 100644 (file)
--- a/src/black/trans.py
+++ b/src/black/trans.py
@@ -4,7 +4,7 @@ String transformers that can split and merge strings.
 from abc import ABC, abstractmethod
 from collections import defaultdict
 from dataclasses import dataclass
 from abc import ABC, abstractmethod
 from collections import defaultdict
 from dataclasses import dataclass

-import regex as re  # We need recursive patterns here (?R)
+import re

 from typing import (
     Any,
     Callable,
 from typing import (
     Any,
     Callable,


@@ -24,9 +24,9 @@ from typing import (
 import sys
 
 if sys.version_info < (3, 8):
 import sys
 
 if sys.version_info < (3, 8):

-    from typing_extensions import Final
+    from typing_extensions import Literal, Final

 else:
 else:

-    from typing import Final
+    from typing import Literal, Final

 
 from mypy_extensions import trait
 
 
 from mypy_extensions import trait
 


@@ -71,6 +71,88 @@ def TErr(err_msg: str) -> Err[CannotTransform]:
     return Err(cant_transform)
 
 
     return Err(cant_transform)
 
 

+def hug_power_op(line: Line, features: Collection[Feature]) -> Iterator[Line]:
+    """A transformer which normalizes spacing around power operators."""
+
+    # Performance optimization to avoid unnecessary Leaf clones and other ops.
+    for leaf in line.leaves:
+        if leaf.type == token.DOUBLESTAR:
+            break
+    else:
+        raise CannotTransform("No doublestar token was found in the line.")
+
+    def is_simple_lookup(index: int, step: Literal[1, -1]) -> bool:
+        # Brackets and parentheses indicate calls, subscripts, etc. ...
+        # basically stuff that doesn't count as "simple". Only a NAME lookup
+        # or dotted lookup (eg. NAME.NAME) is OK.
+        if step == -1:
+            disallowed = {token.RPAR, token.RSQB}
+        else:
+            disallowed = {token.LPAR, token.LSQB}
+
+        while 0 <= index < len(line.leaves):
+            current = line.leaves[index]
+            if current.type in disallowed:
+                return False
+            if current.type not in {token.NAME, token.DOT} or current.value == "for":
+                # If the current token isn't disallowed, we'll assume this is simple as
+                # only the disallowed tokens are semantically attached to this lookup
+                # expression we're checking. Also, stop early if we hit the 'for' bit
+                # of a comprehension.
+                return True
+
+            index += step
+
+        return True
+
+    def is_simple_operand(index: int, kind: Literal["base", "exponent"]) -> bool:
+        # An operand is considered "simple" if's a NAME, a numeric CONSTANT, a simple
+        # lookup (see above), with or without a preceding unary operator.
+        start = line.leaves[index]
+        if start.type in {token.NAME, token.NUMBER}:
+            return is_simple_lookup(index, step=(1 if kind == "exponent" else -1))
+
+        if start.type in {token.PLUS, token.MINUS, token.TILDE}:
+            if line.leaves[index + 1].type in {token.NAME, token.NUMBER}:
+                # step is always one as bases with a preceding unary op will be checked
+                # for simplicity starting from the next token (so it'll hit the check
+                # above).
+                return is_simple_lookup(index + 1, step=1)
+
+        return False
+
+    leaves: List[Leaf] = []
+    should_hug = False
+    for idx, leaf in enumerate(line.leaves):
+        new_leaf = leaf.clone()
+        if should_hug:
+            new_leaf.prefix = ""
+            should_hug = False
+
+        should_hug = (
+            (0 < idx < len(line.leaves) - 1)
+            and leaf.type == token.DOUBLESTAR
+            and is_simple_operand(idx - 1, kind="base")
+            and line.leaves[idx - 1].value != "lambda"
+            and is_simple_operand(idx + 1, kind="exponent")
+        )
+        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,
+    )
+
+

 class StringTransformer(ABC):
     """
     An implementation of the Transformer protocol that relies on its
 class StringTransformer(ABC):
     """
     An implementation of the Transformer protocol that relies on its


@@ -453,7 +535,7 @@ class StringMerger(StringTransformer, CustomSplitMapMixin):
             # with 'f'...
             if "f" in prefix and "f" not in next_prefix:
                 # Then we must escape any braces contained in this substring.
             # with 'f'...
             if "f" in prefix and "f" not in next_prefix:
                 # Then we must escape any braces contained in this substring.

-                SS = re.subf(r"(\{|\})", "{1}{1}", SS)
+                SS = re.sub(r"(\{|\})", r"\1\1", SS)

 
             NSS = make_naked(SS, next_prefix)
 
 
             NSS = make_naked(SS, next_prefix)
 


@@ -942,6 +1024,57 @@ class BaseStringSplitter(StringTransformer):
         return max_string_length
 
 
         return max_string_length
 
 

+def iter_fexpr_spans(s: str) -> Iterator[Tuple[int, int]]:
+    """
+    Yields spans corresponding to expressions in a given f-string.
+    Spans are half-open ranges (left inclusive, right exclusive).
+    Assumes the input string is a valid f-string, but will not crash if the input
+    string is invalid.
+    """
+    stack: List[int] = []  # our curly paren stack
+    i = 0
+    while i < len(s):
+        if s[i] == "{":
+            # if we're in a string part of the f-string, ignore escaped curly braces
+            if not stack and i + 1 < len(s) and s[i + 1] == "{":
+                i += 2
+                continue
+            stack.append(i)
+            i += 1
+            continue
+
+        if s[i] == "}":
+            if not stack:
+                i += 1
+                continue
+            j = stack.pop()
+            # we've made it back out of the expression! yield the span
+            if not stack:
+                yield (j, i + 1)
+            i += 1
+            continue
+
+        # if we're in an expression part of the f-string, fast forward through strings
+        # note that backslashes are not legal in the expression portion of f-strings
+        if stack:
+            delim = None
+            if s[i : i + 3] in ("'''", '"""'):
+                delim = s[i : i + 3]
+            elif s[i] in ("'", '"'):
+                delim = s[i]
+            if delim:
+                i += len(delim)
+                while i < len(s) and s[i : i + len(delim)] != delim:
+                    i += 1
+                i += len(delim)
+                continue
+        i += 1
+
+
+def fstring_contains_expr(s: str) -> bool:
+    return any(iter_fexpr_spans(s))
+
+

 class StringSplitter(BaseStringSplitter, CustomSplitMapMixin):
     """
     StringTransformer that splits "atom" strings (i.e. strings which exist on
 class StringSplitter(BaseStringSplitter, CustomSplitMapMixin):
     """
     StringTransformer that splits "atom" strings (i.e. strings which exist on


@@ -981,17 +1114,6 @@ class StringSplitter(BaseStringSplitter, CustomSplitMapMixin):
     """
 
     MIN_SUBSTR_SIZE: Final = 6
     """
 
     MIN_SUBSTR_SIZE: Final = 6

-    # Matches an "f-expression" (e.g. {var}) that might be found in an f-string.
-    RE_FEXPR: Final = r"""
-    (?<!\{) (?:\{\{)* \{ (?!\{)
-        (?:
-            [^\{\}]
-            | \{\{
-            | \}\}
-            | (?R)
-        )+
-    \}
-    """

 
     def do_splitter_match(self, line: Line) -> TMatchResult:
         LL = line.leaves
 
     def do_splitter_match(self, line: Line) -> TMatchResult:
         LL = line.leaves


@@ -1058,8 +1180,8 @@ class StringSplitter(BaseStringSplitter, CustomSplitMapMixin):
         # contain any f-expressions, but ONLY if the original f-string
         # contains at least one f-expression. Otherwise, we will alter the AST
         # of the program.
         # contain any f-expressions, but ONLY if the original f-string
         # contains at least one f-expression. Otherwise, we will alter the AST
         # of the program.

-        drop_pointless_f_prefix = ("f" in prefix) and re.search(
-            self.RE_FEXPR, LL[string_idx].value, re.VERBOSE
+        drop_pointless_f_prefix = ("f" in prefix) and fstring_contains_expr(
+            LL[string_idx].value

         )
 
         first_string_line = True
         )
 
         first_string_line = True


@@ -1299,9 +1421,7 @@ class StringSplitter(BaseStringSplitter, CustomSplitMapMixin):
         """
         if "f" not in get_string_prefix(string).lower():
             return
         """
         if "f" not in get_string_prefix(string).lower():
             return

-
-        for match in re.finditer(self.RE_FEXPR, string, re.VERBOSE):
-            yield match.span()
+        yield from iter_fexpr_spans(string)

 
     def _get_illegal_split_indices(self, string: str) -> Set[Index]:
         illegal_indices: Set[Index] = set()
 
     def _get_illegal_split_indices(self, string: str) -> Set[Index]:
         illegal_indices: Set[Index] = set()


@@ -1417,7 +1537,7 @@ class StringSplitter(BaseStringSplitter, CustomSplitMapMixin):
         """
         assert_is_leaf_string(string)
 
         """
         assert_is_leaf_string(string)
 

-        if "f" in prefix and not re.search(self.RE_FEXPR, string, re.VERBOSE):
+        if "f" in prefix and not fstring_contains_expr(string):

             new_prefix = prefix.replace("f", "")
 
             temp = string[len(prefix) :]
             new_prefix = prefix.replace("f", "")
 
             temp = string[len(prefix) :]