IDLE: make use of extended error info.

[terryjreedy]

BPO	47156
Nosy	@terryjreedy, @aroberge

^{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 = 'https://github.com/terryjreedy'
closed_at = None
created_at = <Date 2022-03-29.22:10:53.350>
labels = ['expert-IDLE', '3.10', '3.11']
title = 'IDLE: make use of extended SyntaxError info.'
updated_at = <Date 2022-03-30.00:59:30.437>
user = 'https://github.com/terryjreedy'

bugs.python.org fields:

activity = <Date 2022-03-30.00:59:30.437>
actor = 'aroberge'
assignee = 'terry.reedy'
closed = False
closed_date = None
closer = None
components = ['IDLE']
creation = <Date 2022-03-29.22:10:53.350>
creator = 'terry.reedy'
dependencies = []
files = []
hgrepos = []
issue_num = 47156
keywords = []
message_count = 2.0
messages = ['416302', '416315']
nosy_count = 2.0
nosy_names = ['terry.reedy', 'aroberge']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'test needed'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue47156'
versions = ['Python 3.10', 'Python 3.11']

[terryjreedy]

In 3.10 and 3.11:

>>> while s := input.read(MAXBINSIZE):
...     while len(s) < MAXBINSIZE and ns := input.read(MAXBINSIZE-len(s)):
  File "<stdin>", line 2
    while len(s) < MAXBINSIZE and ns := input.read(MAXBINSIZE-len(s)):
          ^^^^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: cannot use assignment expressions with expression

IDLE only colors the 'l' of 'len'; add extended marking.

At least in 3.11, some non-syntax errors have 'fine-grained markings'.

x = {'a': {'b': None}}
x['a']['b']['c']['d'] = 1
print(x['a']['b']['c']['d'])

$ python3.11 test.py
Traceback (most recent call last):
  File "/data/shared/lusers/enneking/test.py", line 4 in <module>
    x['a']['b']['c']['d'] = 1
    ~~~~~~~~~~~^^^^^
TypeError: 'NoneType' object is not subscriptable

Adding colors may require monkeypatching method or subclassing class in traceback.py. May have commented on traceback issue or PR. Or perhaps use sys._excepthook instead of current code and replace ~^ with colors as print. Note that present on each of multiple lines.

Would have to decide on how to differentiate ~ context versus ^ error site. Could initially not. Or use color 'diluted' with white or foreground or background or mixture color? (Experiment needed.)

Related: Put interactive SyntaxErrors in box.

EDIT: Anyone really want a log of error that occurred during a session?

Andre Roberge would like the last error accessible

[aroberge]

(Anyone really want log of error?)

If by this you mean having access to the error from a known place (like sys.last_traceback or something else specific to IDLE but available from a script), then the answer from me is definitely yes.

[terryjreedy]

I clarified my question above as meaning a (recording) of all errors in a session included in the shell output that can be saved to a file. This would be a different issue. So would accessibility from a script. I don't remember if Mar 29 is before or after I patched run.py to improve this.