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Fix incorrect linenos on fstring tokens with escaped newlines (#4423)
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I don't think this can affect Black itself much (maybe for formatting
ranges), but I ran into this with https://github.com/JelleZijlstra/lib2toast
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JelleZijlstra authored Aug 1, 2024
1 parent 7fa1faf commit 4b4ae43
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3 changes: 3 additions & 0 deletions CHANGES.md
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Expand Up @@ -39,6 +39,9 @@

- Fix bug with Black incorrectly parsing empty lines with a backslash (#4343)

- Fix incorrect line numbers in the tokenizer for certain tokens within f-strings
(#4423)

### Performance

<!-- Changes that improve Black's performance. -->
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2 changes: 1 addition & 1 deletion src/blib2to3/pgen2/tokenize.py
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Expand Up @@ -638,7 +638,7 @@ def generate_tokens(
else:
if is_fstring_start(token):
fstring_start, token = _split_fstring_start_and_middle(token)
fstring_start_epos = (lnum, spos[1] + len(fstring_start))
fstring_start_epos = (spos[0], spos[1] + len(fstring_start))
yield (
FSTRING_START,
fstring_start,
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120 changes: 120 additions & 0 deletions tests/test_tokenize.py
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"""Tests for the blib2to3 tokenizer."""

import io
import sys
import textwrap
from dataclasses import dataclass
from typing import List

import black
from blib2to3.pgen2 import token, tokenize


@dataclass
class Token:
type: str
string: str
start: tokenize.Coord
end: tokenize.Coord


def get_tokens(text: str) -> List[Token]:
"""Return the tokens produced by the tokenizer."""
readline = io.StringIO(text).readline
tokens: List[Token] = []

def tokeneater(
type: int, string: str, start: tokenize.Coord, end: tokenize.Coord, line: str
) -> None:
tokens.append(Token(token.tok_name[type], string, start, end))

tokenize.tokenize(readline, tokeneater)
return tokens


def assert_tokenizes(text: str, tokens: List[Token]) -> None:
"""Assert that the tokenizer produces the expected tokens."""
actual_tokens = get_tokens(text)
assert actual_tokens == tokens


def test_simple() -> None:
assert_tokenizes(
"1",
[Token("NUMBER", "1", (1, 0), (1, 1)), Token("ENDMARKER", "", (2, 0), (2, 0))],
)
assert_tokenizes(
"'a'",
[
Token("STRING", "'a'", (1, 0), (1, 3)),
Token("ENDMARKER", "", (2, 0), (2, 0)),
],
)
assert_tokenizes(
"a",
[Token("NAME", "a", (1, 0), (1, 1)), Token("ENDMARKER", "", (2, 0), (2, 0))],
)


def test_fstring() -> None:
assert_tokenizes(
'f"x"',
[
Token("FSTRING_START", 'f"', (1, 0), (1, 2)),
Token("FSTRING_MIDDLE", "x", (1, 2), (1, 3)),
Token("FSTRING_END", '"', (1, 3), (1, 4)),
Token("ENDMARKER", "", (2, 0), (2, 0)),
],
)
assert_tokenizes(
'f"{x}"',
[
Token("FSTRING_START", 'f"', (1, 0), (1, 2)),
Token("FSTRING_MIDDLE", "", (1, 2), (1, 2)),
Token("LBRACE", "{", (1, 2), (1, 3)),
Token("NAME", "x", (1, 3), (1, 4)),
Token("RBRACE", "}", (1, 4), (1, 5)),
Token("FSTRING_MIDDLE", "", (1, 5), (1, 5)),
Token("FSTRING_END", '"', (1, 5), (1, 6)),
Token("ENDMARKER", "", (2, 0), (2, 0)),
],
)
assert_tokenizes(
'f"{x:y}"\n',
[
Token(type="FSTRING_START", string='f"', start=(1, 0), end=(1, 2)),
Token(type="FSTRING_MIDDLE", string="", start=(1, 2), end=(1, 2)),
Token(type="LBRACE", string="{", start=(1, 2), end=(1, 3)),
Token(type="NAME", string="x", start=(1, 3), end=(1, 4)),
Token(type="OP", string=":", start=(1, 4), end=(1, 5)),
Token(type="FSTRING_MIDDLE", string="y", start=(1, 5), end=(1, 6)),
Token(type="RBRACE", string="}", start=(1, 6), end=(1, 7)),
Token(type="FSTRING_MIDDLE", string="", start=(1, 7), end=(1, 7)),
Token(type="FSTRING_END", string='"', start=(1, 7), end=(1, 8)),
Token(type="NEWLINE", string="\n", start=(1, 8), end=(1, 9)),
Token(type="ENDMARKER", string="", start=(2, 0), end=(2, 0)),
],
)
assert_tokenizes(
'f"x\\\n{a}"\n',
[
Token(type="FSTRING_START", string='f"', start=(1, 0), end=(1, 2)),
Token(type="FSTRING_MIDDLE", string="x\\\n", start=(1, 2), end=(2, 0)),
Token(type="LBRACE", string="{", start=(2, 0), end=(2, 1)),
Token(type="NAME", string="a", start=(2, 1), end=(2, 2)),
Token(type="RBRACE", string="}", start=(2, 2), end=(2, 3)),
Token(type="FSTRING_MIDDLE", string="", start=(2, 3), end=(2, 3)),
Token(type="FSTRING_END", string='"', start=(2, 3), end=(2, 4)),
Token(type="NEWLINE", string="\n", start=(2, 4), end=(2, 5)),
Token(type="ENDMARKER", string="", start=(3, 0), end=(3, 0)),
],
)


# Run "echo some code | python tests/test_tokenize.py" to generate test cases.
if __name__ == "__main__":
code = sys.stdin.read()
tokens = get_tokens(code)
text = f"assert_tokenizes({code!r}, {tokens!r})"
text = black.format_str(text, mode=black.Mode())
print(textwrap.indent(text, " "))

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