[New-bugs-announce] [issue40612] Make traceback module's formatting of SyntaxError more similar to system formatting

[Guido van Rossum]

New submission from Guido van Rossum <guido at python.org>:

The traceback module formats several edge cases of SyntaxError different than CPython's default formatting.

- There's an off-by-one error if the column offset (printed as a caret) points past the last character (example: 'a +='). The clipping is wrong and the caret points to the last character.

- If the offset is <= 0, it appears the code silently adds the length of the source text.

- The system formatting suppresses the caret if the offset is -1; the only way to suppress the caret with the traceback module is setting the offset to None (or setting the source text to None).

- The system formatting can position the caret way past the end of the source text; the traceback module clips (also see the first bullet).

I propose to make the traceback module behave the same way as the system module in all cases. I also propose to make both suppress the caret if the offset is <= 0. Finally I propose to make the system formatting limit the offset to just past the end of the source text.

I propose not to bother changing anything in 3.8 or before.

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messages: 368759
nosy: gvanrossum, lys.nikolaou, pablogsal
priority: normal
severity: normal
status: open
title: Make traceback module's formatting of SyntaxError more similar to system formatting
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40612>
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