Re: [Trac] RuntimeError in tracoverlayview/web_ui.py when iterating over MIME types with Python 2.7

On Thu, Jun 18, 2026 at 6:08=E2=80=AFPM Ma=C3=ABl <mael.fcbarcelone@outlook=
.fr> wrote:
>
> Hello,
>
> We encountered a runtime issue with the tracoverlayview plugin when runni=
ng under Python 2.7.
>
> The error is caused by iterating over a dictionary while it may be modifi=
ed during the loop. In our case, the issue occurs in tracoverlayview/web_ui=
.py, in the _get_mimetypes() method:
> for ext, mimetype in _iteritems(map_):
>
> This can raise the following error:
> RuntimeError: dictionary changed size during iteration
>
> We applied the following local patch to iterate over a static list of ite=
ms instead:
> for ext, mimetype in list(_iteritems(map_)):
>
> Suggested patch:
> -            for ext, mimetype in _iteritems(map_):
> +           for ext, mimetype in list(_iteritems(map_)):
>
> This fixes the issue in our environment.
> Thank you.

Thanks for the reporting. But unable to reproduce the issue. Also,
very weird. The "map_" is not modified after initialized by Trac core
and mimetypes module. I don't believe the error is raised.

--=20
Jun Omae <[email protected]> (=E5=A4=A7=E5=89=8D =E6=BD=A4)

--=20
You received this message because you are subscribed to the Google Groups "=
Trac Users" group.
To unsubscribe from this group and stop receiving emails from it, send an e=
mail to trac-users+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/[email protected]
To view this discussion visit https://groups.google.com/d/msgid/trac-users/=
CAEVLMahymUhWNE2XccBOxbgqyzVTgOY%2Ba9U-RDh6RJ3uhDFiaQ%40mail.gmail.com.