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tokenizer: skip lines that are just slash and whitespace #4343

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merged 8 commits into from
Jun 1, 2024
Merged

tokenizer: skip lines that are just slash and whitespace #4343

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19cc96b
tokenizer: skip lines that are just whitespace
tusharsadhwani Apr 30, 2024
72a84b5
make test 3.10+
tusharsadhwani Apr 30, 2024
44ae615
fix failing test
tusharsadhwani Apr 30, 2024
9daa7e4
add changelog entry
tusharsadhwani Apr 30, 2024
4f91e3b
don't ignore slashes inside strings
tusharsadhwani Apr 30, 2024
339fd0d
Add name to authors
tusharsadhwani May 2, 2024
216f836
add \f to indent chars
tusharsadhwani May 4, 2024
2313537
fix failing test
tusharsadhwani May 4, 2024
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1 change: 1 addition & 0 deletions AUTHORS.md
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Expand Up @@ -181,6 +181,7 @@ Multiple contributions by:
- [Tony Narlock](mailto:tony@git-pull.com)
- [Tsuyoshi Hombashi](mailto:tsuyoshi.hombashi@gmail.com)
- [Tushar Chandra](mailto:tusharchandra2018@u.northwestern.edu)
- [Tushar Sadhwani](mailto:tushar.sadhwani000@gmail.com)
- [Tzu-ping Chung](mailto:uranusjr@gmail.com)
- [Utsav Shah](mailto:ukshah2@illinois.edu)
- utsav-dbx
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2 changes: 2 additions & 0 deletions CHANGES.md
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Expand Up @@ -29,6 +29,8 @@
- Fix regression where Black failed to parse a multiline f-string containing another
multiline string (#4339)

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

### Performance

<!-- Changes that improve Black's performance. -->
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6 changes: 6 additions & 0 deletions src/blib2to3/pgen2/tokenize.py
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Expand Up @@ -608,6 +608,12 @@ def generate_tokens(
except StopIteration:
line = ""
lnum += 1

# skip lines that are just a slash, to avoid storing that line's
# indent information.
if not contstr and line.rstrip("\n").strip(" \t") == "\\":
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Is this equivalent to just line.strip() == "\\"? Or do we need to care about exotic whitespace characters that are not newline/space/tab?

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I'm not entirely sure, so I tried to be conservative. Does Python normally treat characters like \r or \v as part of indentation?

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Not too sure, there is code in our tokenizer that deals with \f at least. In CPython (Parser/lexer/lexer.c) I see some code dealing with \r and with \f (\014).

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$ printf 'def foo():\n \t pass' | python -m tokenize
1,0-1,3:            NAME           'def'
1,4-1,7:            NAME           'foo'
1,7-1,8:            OP             '('
1,8-1,9:            OP             ')'
1,9-1,10:           OP             ':'
1,10-1,11:          NEWLINE        '\n'
2,0-2,3:            INDENT         ' \t '
2,3-2,7:            NAME           'pass'
2,7-2,8:            NEWLINE        ''
3,0-3,0:            DEDENT         ''
3,0-3,0:            ENDMARKER      ''

$ printf 'def foo():\n \f pass' | python -m tokenize
1,0-1,3:            NAME           'def'
1,4-1,7:            NAME           'foo'
1,7-1,8:            OP             '('
1,8-1,9:            OP             ')'
1,9-1,10:           OP             ':'
1,10-1,11:          NEWLINE        '\n'
2,0-2,3:            INDENT         ' \x0c '
2,3-2,7:            NAME           'pass'
2,7-2,8:            NEWLINE        ''
3,0-3,0:            DEDENT         ''
3,0-3,0:            ENDMARKER      ''

$ printf 'def foo():\n \r pass' | python -m tokenize
1,0-1,3:            NAME           'def'
1,4-1,7:            NAME           'foo'
1,7-1,8:            OP             '('
1,8-1,9:            OP             ')'
1,9-1,10:           OP             ':'
1,10-1,11:          NEWLINE        '\n'
2,1-2,3:            OP             '\r '
2,3-2,7:            NAME           'pass'
2,7-2,8:            NEWLINE        ''
3,0-3,0:            ENDMARKER      ''

So \f is infact legitimate indentation, how interesting.

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$ python -c 'print("def foo():\n \v pass")' | python -m tokenize
1,0-1,3:            NAME           'def'
1,4-1,7:            NAME           'foo'
1,7-1,8:            OP             '('
1,8-1,9:            OP             ')'
1,9-1,10:           OP             ':'
1,10-1,11:          NEWLINE        '\n'
2,0-2,1:            INDENT         ' '
<stdin>:2:2: error: invalid non-printable character U+000B

\v is unparseable.

So editing the PR to do .lstrip(' \t\f') should take care of all cases I believe.

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Made changes. The reason I can't do .strip() is because \ must be at the end of the line. If there's spaces after the backslash it's no longer escaping the newline:

$ printf 'print(2 + \\\n3)'
print(2 + \
3)

$ printf 'print(2 + \\\n3)' | python3
5

$ printf 'print(2 + \\ \n3)' | python3
  File "<stdin>", line 1
    print(2 + \
               ^
SyntaxError: unexpected character after line continuation character

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form_feeds.py contains a \f\ (line 42) that is getting preserved, while the line was being deleted entirely before. Which I think is fine.

continue

pos, max = 0, len(line)

if contstr: # continued string
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24 changes: 24 additions & 0 deletions tests/data/cases/backslash_before_indent.py
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@@ -0,0 +1,24 @@
# flags: --minimum-version=3.10
class Plotter:
\
pass

class AnotherCase:
\
"""Some
\
Docstring
"""

# output

class Plotter:

pass


class AnotherCase:
"""Some
\
Docstring
"""
4 changes: 3 additions & 1 deletion tests/data/cases/comment_after_escaped_newline.py
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Expand Up @@ -14,5 +14,7 @@ def bob(): # pylint: disable=W9016
pass


def bobtwo(): # some comment here
def bobtwo():
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# some comment here
pass