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`invalid-character-backspace` (`PLE2510`)

crates/ruff_linter/resources/mdtest/pylint/invalid-character-backspace.md

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invalid-character-backspace (PLE2510)

Before Python 3.12

toml
target-version = "py39"

[lint]
select = ["PLE2510"]

Replacement fields

Fixes are suppressed when replacing the backspace would introduce an escape sequence into an f-string replacement field. A nested f-string's literal text is still part of an outer replacement field.

py
replacement_field = f"{''}"  # snapshot: invalid-character-backspace
nested_f_string = f"{f'hello'}"  # snapshot: invalid-character-backspace
snapshot
error[PLE2510]: Invalid unescaped character backspace, use "\b" instead
 --> src/mdtest_snippet.py:1:25
  |
1 | replacement_field = f"{'␈'}"  # snapshot: invalid-character-backspace
  |                         ^
  |
help: Replace with escape sequence


error[PLE2510]: Invalid unescaped character backspace, use "\b" instead
 --> src/mdtest_snippet.py:2:29
  |
2 | nested_f_string = f"{f'hello␈'}"  # snapshot: invalid-character-backspace
  |                             ^
  |
help: Replace with escape sequence

Format specs and literal parts

However, escapes are valid in format specs and literal f-string text:

py
format_spec = f"{value:}"  # snapshot: invalid-character-backspace
f_string_literal = f"hello"  # snapshot: invalid-character-backspace
snapshot
error[PLE2510]: Invalid unescaped character backspace, use "\b" instead
 --> src/mdtest_snippet.py:1:24
  |
1 | format_spec = f"{value:␈}"  # snapshot: invalid-character-backspace
  |                        ^
  |
help: Replace with escape sequence
  - format_spec = f"{value:␈}"  # snapshot: invalid-character-backspace
1 + format_spec = f"{value:\b}"  # snapshot: invalid-character-backspace
2 | f_string_literal = f"hello␈"  # snapshot: invalid-character-backspace


error[PLE2510]: Invalid unescaped character backspace, use "\b" instead
 --> src/mdtest_snippet.py:2:27
  |
2 | f_string_literal = f"hello␈"  # snapshot: invalid-character-backspace
  |                           ^
  |
help: Replace with escape sequence
1 | format_spec = f"{value:␈}"  # snapshot: invalid-character-backspace
  - f_string_literal = f"hello␈"  # snapshot: invalid-character-backspace
2 + f_string_literal = f"hello\b"  # snapshot: invalid-character-backspace

Python 3.12 and later

toml
target-version = "py312"

[lint]
select = ["PLE2510"]

PEP 701 permits escape sequences in replacement fields, so all of these fixes are available.

py
replacement_field = f"{''}"  # snapshot: invalid-character-backspace
format_spec = f"{value:}"  # snapshot: invalid-character-backspace
f_string_literal = f"hello"  # snapshot: invalid-character-backspace
nested_f_string = f"{f'hello'}"  # snapshot: invalid-character-backspace
snapshot
error[PLE2510]: Invalid unescaped character backspace, use "\b" instead
 --> src/mdtest_snippet.py:1:25
  |
1 | replacement_field = f"{'␈'}"  # snapshot: invalid-character-backspace
  |                         ^
  |
help: Replace with escape sequence
  - replacement_field = f"{'␈'}"  # snapshot: invalid-character-backspace
1 + replacement_field = f"{'\b'}"  # snapshot: invalid-character-backspace
2 | format_spec = f"{value:␈}"  # snapshot: invalid-character-backspace
3 | f_string_literal = f"hello␈"  # snapshot: invalid-character-backspace
4 | nested_f_string = f"{f'hello␈'}"  # snapshot: invalid-character-backspace


error[PLE2510]: Invalid unescaped character backspace, use "\b" instead
 --> src/mdtest_snippet.py:2:24
  |
2 | format_spec = f"{value:␈}"  # snapshot: invalid-character-backspace
  |                        ^
  |
help: Replace with escape sequence
1 | replacement_field = f"{'␈'}"  # snapshot: invalid-character-backspace
  - format_spec = f"{value:␈}"  # snapshot: invalid-character-backspace
2 + format_spec = f"{value:\b}"  # snapshot: invalid-character-backspace
3 | f_string_literal = f"hello␈"  # snapshot: invalid-character-backspace
4 | nested_f_string = f"{f'hello␈'}"  # snapshot: invalid-character-backspace


error[PLE2510]: Invalid unescaped character backspace, use "\b" instead
 --> src/mdtest_snippet.py:3:27
  |
3 | f_string_literal = f"hello␈"  # snapshot: invalid-character-backspace
  |                           ^
  |
help: Replace with escape sequence
1 | replacement_field = f"{'␈'}"  # snapshot: invalid-character-backspace
2 | format_spec = f"{value:␈}"  # snapshot: invalid-character-backspace
  - f_string_literal = f"hello␈"  # snapshot: invalid-character-backspace
3 + f_string_literal = f"hello\b"  # snapshot: invalid-character-backspace
4 | nested_f_string = f"{f'hello␈'}"  # snapshot: invalid-character-backspace


error[PLE2510]: Invalid unescaped character backspace, use "\b" instead
 --> src/mdtest_snippet.py:4:29
  |
4 | nested_f_string = f"{f'hello␈'}"  # snapshot: invalid-character-backspace
  |                             ^
  |
help: Replace with escape sequence
1 | replacement_field = f"{'␈'}"  # snapshot: invalid-character-backspace
2 | format_spec = f"{value:␈}"  # snapshot: invalid-character-backspace
3 | f_string_literal = f"hello␈"  # snapshot: invalid-character-backspace
  - nested_f_string = f"{f'hello␈'}"  # snapshot: invalid-character-backspace
4 + nested_f_string = f"{f'hello\b'}"  # snapshot: invalid-character-backspace