StructlogProcessor fails typechecking

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Assessment

Difficulty
1/5
Estimated time
Under an hour
Newbie friendliness
35/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Stale
Tech stack
python
Domain
observability-sre

Research direction

Start at StructlogFormatter.call and inspect its event_dict type annotation. Reproduce the issue with the provided mypy example, update the annotation so it accepts the required mutable mapping type, and confirm that mypy no longer reports the list-item error.

Written by the indexing model from the issue text.

Description

agent-python community triage

When typechecking the following code:

from structlog.typing import Processor

shared_processors: tuple[Processor, ...] = (
    structlog.contextvars.merge_contextvars,
    structlog.processors.add_log_level,
    structlog.processors.StackInfoRenderer(),
    structlog.dev.set_exc_info,
    structlog.processors.TimeStamper(fmt="iso", utc=True),
)

processors: list[Processor]
if sys.stderr.isatty():
    processors = [
        *shared_processors,
        structlog.dev.ConsoleRenderer(),
    ]
else:
    processors = [
        *shared_processors,
        structlog.processors.dict_tracebacks,
        ecs_logging.StructlogFormatter(),
    ]

structlog.configure(
    processors=processors,
    logger_factory=structlog.PrintLoggerFactory(),
    cache_logger_on_first_use=True,
)

mypy raises the following:

error: List item 2 has incompatible type "StructlogFormatter"; expected
"Callable[[Any, str, MutableMapping[str, Any]], Union[Mapping[str, Any], str, bytes, bytearray, tuple[Any, ...]]]"  [list-item]
            ecs_logging.StructlogFormatter(),
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
note: "StructlogFormatter.__call__" has type "Callable[[Arg(Any, '_'), Arg(str, 'name'), Arg(dict[str, Any], 'event_dict')], str]"

StructlogFormatter is annotated as accepting a dict[str, Any], but it needs to accept any MutableMapping[str, Any]. The code already conforms to this, so addressing this issue wil hopefully only involve updating the type annotation.

Dominant language
Python
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Forks
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Avg merge
9h 3m
Merged PRs (30d)
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