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blackd: show default values for options (#3712)
[etc/vim.git] / src / black / strings.py
index 5b443ddebc9e7e662b469b2c2717052ff2dcbf99..ac18aef51ed7d7349f0f0bbb4e2dc3ce338c763b 100644 (file)
@@ -2,12 +2,34 @@
 Simple formatting on strings. Further string formatting code is in trans.py.
 """
 
-import regex as re
+import re
 import sys
-from typing import List, Pattern
-
-
-STRING_PREFIX_CHARS = "furbFURB"  # All possible string prefix characters.
+from functools import lru_cache
+from typing import List, Match, Pattern
+
+from blib2to3.pytree import Leaf
+
+if sys.version_info < (3, 8):
+    from typing_extensions import Final
+else:
+    from typing import Final
+
+from black._width_table import WIDTH_TABLE
+
+STRING_PREFIX_CHARS: Final = "furbFURB"  # All possible string prefix characters.
+STRING_PREFIX_RE: Final = re.compile(
+    r"^([" + STRING_PREFIX_CHARS + r"]*)(.*)$", re.DOTALL
+)
+FIRST_NON_WHITESPACE_RE: Final = re.compile(r"\s*\t+\s*(\S)")
+UNICODE_ESCAPE_RE: Final = re.compile(
+    r"(?P<backslashes>\\+)(?P<body>"
+    r"(u(?P<u>[a-fA-F0-9]{4}))"  # Character with 16-bit hex value xxxx
+    r"|(U(?P<U>[a-fA-F0-9]{8}))"  # Character with 32-bit hex value xxxxxxxx
+    r"|(x(?P<x>[a-fA-F0-9]{2}))"  # Character with hex value hh
+    r"|(N\{(?P<N>[a-zA-Z0-9 \-]{2,})\})"  # Character named name in the Unicode database
+    r")",
+    re.VERBOSE,
+)
 
 
 def sub_twice(regex: Pattern[str], replacement: str, original: str) -> str:
@@ -37,7 +59,7 @@ def lines_with_leading_tabs_expanded(s: str) -> List[str]:
     for line in s.splitlines():
         # Find the index of the first non-whitespace character after a string of
         # whitespace that includes at least one tab
-        match = re.match(r"\s*\t+\s*(\S)", line)
+        match = FIRST_NON_WHITESPACE_RE.match(line)
         if match:
             first_non_whitespace_idx = match.start(1)
 
@@ -87,7 +109,7 @@ def get_string_prefix(string: str) -> str:
     prefix = ""
     prefix_idx = 0
     while string[prefix_idx] in STRING_PREFIX_CHARS:
-        prefix += string[prefix_idx].lower()
+        prefix += string[prefix_idx]
         prefix_idx += 1
 
     return prefix
@@ -128,20 +150,32 @@ def assert_is_leaf_string(string: str) -> None:
     ), f"{set(string[:quote_idx])} is NOT a subset of {set(STRING_PREFIX_CHARS)}."
 
 
-def normalize_string_prefix(s: str, remove_u_prefix: bool = False) -> str:
-    """Make all string prefixes lowercase.
-
-    If remove_u_prefix is given, also removes any u prefix from the string.
-    """
-    match = re.match(r"^([" + STRING_PREFIX_CHARS + r"]*)(.*)$", s, re.DOTALL)
+def normalize_string_prefix(s: str) -> str:
+    """Make all string prefixes lowercase."""
+    match = STRING_PREFIX_RE.match(s)
     assert match is not None, f"failed to match string {s!r}"
     orig_prefix = match.group(1)
-    new_prefix = orig_prefix.replace("F", "f").replace("B", "b").replace("U", "u")
-    if remove_u_prefix:
-        new_prefix = new_prefix.replace("u", "")
+    new_prefix = (
+        orig_prefix.replace("F", "f")
+        .replace("B", "b")
+        .replace("U", "")
+        .replace("u", "")
+    )
+
+    # Python syntax guarantees max 2 prefixes and that one of them is "r"
+    if len(new_prefix) == 2 and "r" != new_prefix[0].lower():
+        new_prefix = new_prefix[::-1]
     return f"{new_prefix}{match.group(2)}"
 
 
+# Re(gex) does actually cache patterns internally but this still improves
+# performance on a long list literal of strings by 5-9% since lru_cache's
+# caching overhead is much lower.
+@lru_cache(maxsize=64)
+def _cached_compile(pattern: str) -> Pattern[str]:
+    return re.compile(pattern)
+
+
 def normalize_string_quotes(s: str) -> str:
     """Prefer double quotes but only if it doesn't cause more escaping.
 
@@ -166,9 +200,9 @@ def normalize_string_quotes(s: str) -> str:
         return s  # There's an internal error
 
     prefix = s[:first_quote_pos]
-    unescaped_new_quote = re.compile(rf"(([^\\]|^)(\\\\)*){new_quote}")
-    escaped_new_quote = re.compile(rf"([^\\]|^)\\((?:\\\\)*){new_quote}")
-    escaped_orig_quote = re.compile(rf"([^\\]|^)\\((?:\\\\)*){orig_quote}")
+    unescaped_new_quote = _cached_compile(rf"(([^\\]|^)(\\\\)*){new_quote}")
+    escaped_new_quote = _cached_compile(rf"([^\\]|^)\\((?:\\\\)*){new_quote}")
+    escaped_orig_quote = _cached_compile(rf"([^\\]|^)\\((?:\\\\)*){orig_quote}")
     body = s[first_quote_pos + len(orig_quote) : -len(orig_quote)]
     if "r" in prefix.casefold():
         if unescaped_new_quote.search(body):
@@ -190,9 +224,9 @@ def normalize_string_quotes(s: str) -> str:
     if "f" in prefix.casefold():
         matches = re.findall(
             r"""
-            (?:[^{]|^)\{  # start of the string or a non-{ followed by a single {
+            (?:(?<!\{)|^)\{  # start of the string or a non-{ followed by a single {
                 ([^{].*?)  # contents of the brackets except if begins with {{
-            \}(?:[^}]|$)  # A } followed by end of the string or a non-}
+            \}(?:(?!\})|$)  # A } followed by end of the string or a non-}
             """,
             new_body,
             re.VERBOSE,
@@ -214,3 +248,88 @@ def normalize_string_quotes(s: str) -> str:
         return s  # Prefer double quotes
 
     return f"{prefix}{new_quote}{new_body}{new_quote}"
+
+
+def normalize_unicode_escape_sequences(leaf: Leaf) -> None:
+    """Replace hex codes in Unicode escape sequences with lowercase representation."""
+    text = leaf.value
+    prefix = get_string_prefix(text)
+    if "r" in prefix.lower():
+        return
+
+    def replace(m: Match[str]) -> str:
+        groups = m.groupdict()
+        back_slashes = groups["backslashes"]
+
+        if len(back_slashes) % 2 == 0:
+            return back_slashes + groups["body"]
+
+        if groups["u"]:
+            # \u
+            return back_slashes + "u" + groups["u"].lower()
+        elif groups["U"]:
+            # \U
+            return back_slashes + "U" + groups["U"].lower()
+        elif groups["x"]:
+            # \x
+            return back_slashes + "x" + groups["x"].lower()
+        else:
+            assert groups["N"], f"Unexpected match: {m}"
+            # \N{}
+            return back_slashes + "N{" + groups["N"].upper() + "}"
+
+    leaf.value = re.sub(UNICODE_ESCAPE_RE, replace, text)
+
+
+@lru_cache(maxsize=4096)
+def char_width(char: str) -> int:
+    """Return the width of a single character as it would be displayed in a
+    terminal or editor (which respects Unicode East Asian Width).
+
+    Full width characters are counted as 2, while half width characters are
+    counted as 1.  Also control characters are counted as 0.
+    """
+    table = WIDTH_TABLE
+    codepoint = ord(char)
+    highest = len(table) - 1
+    lowest = 0
+    idx = highest // 2
+    while True:
+        start_codepoint, end_codepoint, width = table[idx]
+        if codepoint < start_codepoint:
+            highest = idx - 1
+        elif codepoint > end_codepoint:
+            lowest = idx + 1
+        else:
+            return 0 if width < 0 else width
+        if highest < lowest:
+            break
+        idx = (highest + lowest) // 2
+    return 1
+
+
+def str_width(line_str: str) -> int:
+    """Return the width of `line_str` as it would be displayed in a terminal
+    or editor (which respects Unicode East Asian Width).
+
+    You could utilize this function to determine, for example, if a string
+    is too wide to display in a terminal or editor.
+    """
+    if line_str.isascii():
+        # Fast path for a line consisting of only ASCII characters
+        return len(line_str)
+    return sum(map(char_width, line_str))
+
+
+def count_chars_in_width(line_str: str, max_width: int) -> int:
+    """Count the number of characters in `line_str` that would fit in a
+    terminal or editor of `max_width` (which respects Unicode East Asian
+    Width).
+    """
+    total_width = 0
+    for i, char in enumerate(line_str):
+        width = char_width(char)
+        if width + total_width > max_width:
+            return i
+        total_width += width
+    return len(line_str)