(🐞) Column marker in error message off for certain string errors

[KotlinIsland]

"\N{a}"

👉 python test.py
  File "/test.py", line 1
    "\N{a}"
           ^
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 0-4: unknown Unicode character name

Here the caret is pointing to blackspace after the code

Expected

👉 python test.py
  File "/test.py", line 1
    "\N{a}"
        ^
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 0-4: unknown Unicode character name

[arhadthedev]

Reproduced in the CLI too:

>>> "\N{a}"
  File "<stdin>", line 1
    "\N{a}"
           ^
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 0-4: unknown Unicode character name

By the way, the interpreter hangs for around five seconds on first execution of \N{a} with no delay on further attempts.

[KotlinIsland]

@arhadthedev Am I missing something? I Can't see any caret in your repro.

[arhadthedev]

@KotlinIsland Thank you, updated my initially undercopied output.

[arhadthedev]

@benjaminp, @pablogsal (as parser experts)

update: @gvanrossum, @lysnikolaou (as new parser experts)

[terryjreedy]

This is likely a duplicate of #102310.
Testing with Python 3.12.0a5+ (heads/main:0f89acf6cc, Feb 27 2023, 21:33:28), message is "incomplete input" and closing quote is marked. I interpret this as having been fixed already.
EDIT: the different message is because I initially ran in IDLE, which uses codeop, which uses compile slightly differently.
Get same messages in REPL compiled 2 hours ago and in installed 3.12.0a5 and installed 3.10.10.

[gvanrossum]

By the way, the interpreter hangs for around five seconds on first execution of \N{a} with no delay on further attempts.

Could that just be importing the (humongous) unicodedata module to resolve the name?

@terryjreedy What is it a duplicate of? Your link points to this same issue.

[gvanrossum]

PS. If Benjamin is still listed as parser expert that's likely out of date.

[terryjreedy]

#102310, about same problem with b"Ā". Sorry about bad link (now fixed).

[KotlinIsland]

I don't think it's the same issue as #102310, in that issue the column marker is offset by a non ascii character, in this issue the marker appears after the string. While this issue does make an appearance in #102310, I do feel that they are distinct.

👉 $c:temp = "'\N{a}'"
👉 py temp
  File "C:\temp", line 1
    '\N{a}'
           ^
👉 $c:temp = "b'Ā'"
👉 py temp
  File "C:\temp", line 1
    b'Ā'
         ^
👉 $c:temp = "b'ĀĀĀĀĀĀĀĀ'"
👉 py temp
  File "C:\temp", line 1
    b'ĀĀĀĀĀĀĀĀ'
                       ^
SyntaxError: bytes can only contain ASCII literal characters
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 0-4: unknown Unicode character name