Double translation about chameleon

[malthe]

I think you're supposed to always return a string from the translate function. This would then mean that __quote would not attempt to convert (i.e. translate) twice.

If in doubt, consult z3c.pt which has existed as an option for people in Zope/Plone to use Chameleon for ages.

[viktordick]

The chameleon cache file contains inside __quote the lines

__converted = convert(target)
target = (str(target) if (target is __converted) else __converted)

suggesting that the translation (convert is a partial on translate) is allowed to return the object itself to indicate that it will not handle it.
Anyhow, if I return str(msgid) instead of msgid in the case of msgid not being a string, the translation is only called once, but I still am unable to differentiate between

<div i18n:translate="" tal:content="x"></div>

and

<div tal:content="x"></div>

Of course, this is actually what the documentation says. x is considered to be in need of translation irrespective of the explict i18n:translate attribute simply due to it being neither a string nor an object with an __html__ method. Whether an explicit translation requesting attribute was also given, is then irrelevant and my translate function is not given any information about whether the attribute is in fact present (short of inspecting the call stack).

I can live with this since in the context of Zope 4, I can only cause this behavior if naming a File object as content for a tag and at the same time requesting a translation using an explicit i18n:translate. I doubt that we actually have this situation anywhere in our code. It is just something that is now different than it was in Zope 2 due to this different definition of what needs to be translated.

Maybe if more such problems arise, you could consider a chameleon flag that changes this behavior to be more compatible to Zope, so it only translates messages with explicit i18n attributes?