Re: [PATCH] perf pmu-events: Fix jevents.py type annotations for mypy 2.x

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Sun, Oct 18, 2026 at 07:53:45AM +0100, Lalit Maganti wrote:
> Since the build runs mypy whenever it is installed, the perf build fails
> with mypy 2.4 on 7 errors in jevents.py, e.g.:
> 
>   pmu-events/jevents.py:542: error: Item "None" of "str | None" has no
>   attribute "replace"  [union-attr]
>   pmu-events/jevents.py:563: error: Item "None" of "BigCString | None"
>   has no attribute "offsets"  [union-attr]
> 
> Both come from wrong annotations rather than from code that can see
> None:
>  - unit_to_pmu() is annotated as returning Optional[str] but always
>    returns a string, so JsonEvent.pmu is typed as optional where it is
>    used as a str.
>  - _bcs is set to None before the BigCString class is defined and only
>    assigned an instance after it, so mypy types it as BigCString | None.
> 
> Correct the return type and declare _bcs with its type instead of the
> None placeholder. The generated pmu-events.c and pmu-events-string.c
> are unchanged, and mypy 1.9 still passes.
> 
> Fixes: b3e9c396d0ac ("perf build: Make mypy build test opt-out (NO_MYPY=1)")
> Assisted-by: LLM
> Signed-off-by: Lalit Maganti <lalitmaganti@gmail.com>

Looks ok,

Thanks, applied for v7.4.

- Arnaldo
> ---
>  tools/perf/pmu-events/jevents.py | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
> index cc143f7e7cdf..080e04b51b8c 100755
> --- a/tools/perf/pmu-events/jevents.py
> +++ b/tools/perf/pmu-events/jevents.py
> @@ -35,7 +35,7 @@ _pending_metrics: list["JsonEvent"] = []
>  # Name of metrics table to be written out
>  _pending_metrics_tblname: Optional[str] = None
>  # Global BigCString shared by all structures.
> -_bcs = None
> +_bcs: "BigCString"
>  # Map from the name of a metric group to a description of the group.
>  _metricgroups: Dict[str, str] = {}
>  # Order specific JsonEvent attributes will be visited.
> @@ -262,7 +262,7 @@ class JsonEvent:
>          return fixed[name.lower()]
>        return event
>  
> -    def unit_to_pmu(unit: Optional[str]) -> Optional[str]:
> +    def unit_to_pmu(unit: Optional[str]) -> str:
>        """Convert a JSON Unit to Linux PMU name."""
>        if not unit:
>          return 'default_core'
> 
> base-commit: 1c90f0a3c8a1c4e38f9edd97af9e20848805a7fb
> -- 
> 2.56.0
>