Improve syntax error for wrongly closed strings

[pablogsal]

BPO	44369
Nosy	@aroberge, @lysnikolaou, @pablogsal, @isidentical
PRs	gh-88535: Improve syntax error for wrongly closed strings #26633

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-06-09.21:15:52.840>
labels = ['interpreter-core', '3.10', '3.11']
title = 'Improve syntax error for wrongly closed strings'
updated_at = <Date 2021-06-14.18:54:32.243>
user = 'https://github.com/pablogsal'

bugs.python.org fields:

activity = <Date 2021-06-14.18:54:32.243>
actor = 'pablogsal'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Parser']
creation = <Date 2021-06-09.21:15:52.840>
creator = 'pablogsal'
dependencies = []
files = []
hgrepos = []
issue_num = 44369
keywords = ['patch']
message_count = 4.0
messages = ['395476', '395491', '395696', '395837']
nosy_count = 4.0
nosy_names = ['aroberge', 'lys.nikolaou', 'pablogsal', 'BTaskaya']
pr_nums = ['26633']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue44369'
versions = ['Python 3.10', 'Python 3.11']

[pablogsal]

Let's asume this string:
"
x = "Cannot recover from "MemoryErrors" while something happnes while "

The line is incorrect because the quotes arround MemoryErrors are the same as the string is used, resulting in STRING + expression + STRING.

Currenly we say:

>>> 'Cannot recover from 'MemoryErrors' while '
  File "<stdin>", line 1
    'Cannot recover from 'MemoryErrors' while '
                          ^
SyntaxError: invalid syntax

but I think it will be a great improvement if we say:

>>> 'Cannot recover from 'MemoryErrors' while '
  File "<stdin>", line 1
    'Cannot recover from 'MemoryErrors' while '
                          ^^^^^^^^^^^^
SyntaxError: invalid syntax. Did you use the same quotes here as the string?

Probably the message should be better, but I think this is a good improvement.

[aroberge]

I like this. While it would be a bit longer, I'm wondering if the message should not read instead as follows:

... Did you use the same quotes here as those enclosing the string?

===

I suspect that errors coming from the use of a single quote, as in:

'Don't do this'

might be just as prevalent if not more so; however, they might be more difficult to properly diagnose.

[isidentical]

From what I can share by my experience, this error happens soo much. So I'd love to see it.

For a more consistent message with others, maybe it could be something like this;

SyntaxError: invalid syntax. Maybe you meant to use a different type of quote

[pablogsal]

One problem with that is that the lookahead will move the error indicator to some incorrect place if the match fails. For example:

PYTHON3.9

>>> "dfssdfsdfsd" fdsf sdfsdfsd {}
  File "<stdin>", line 1
    "dfssdfsdfsd" fdsf sdfsdfsd {}
                  ^
SyntaxError: invalid syntax

with this PR:

>>> "dfssdfsdfsd" fdsf sdfsdfsd {}
  File "<stdin>", line 1
    "dfssdfsdfsd" fdsf sdfsdfsd {}
                                ^
SyntaxError: invalid syntax

We need a solution to this problem first