Don't rely on reprocessing of targets with errors in fine grained mode

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Refactor
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
compilers, testing-qa

Research direction

Start by running the [case testWarnUnusedIgnoresFine] scenario with --warn-unused-ignores and confirm the current failure. Trace how fine-grained mode handles targets with errors and reprocessing, then determine how dependency tracking or cached errors should make the case pass without relying on reprocessing.

Written by the indexing model from the issue text.

Description

needs discussion topic-fine-grained-incremental

Consider this test case:

[case testWarnUnusedIgnoresFine]
# flags: --warn-unused-ignores
import a
[file a.py]
import b
b.x  # type: ignore
[file b.py]
# empty
[file b.py.2]
x = 1
[out]
==
a.py:2: note: unused 'type: ignore' comment

Currently it fails, presumably because we don't reprocess a.py. This however points to a larger potential problem, currently we are relying on reprocessing targets with errors. However, a better idea might be to only rely on fine grained dependencies. Of course, we can cache errors and just show them if a target had errors and was not reprocessed.

Dominant language
Python
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Merged PRs (30d)
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