odoo/odoo#28519 removed large parts of pycompat, but left reraise
despite that not having much value.
Remove that helper and replace it by just a `raise` in most cases:
when raising from an except block, the old exception is automatically
chained to the new one, no need to mess around.
There is one exception: in http we have to re-raise an existing
exception explicitly (aka `raise exc` rather than just `raise).
This is less than ideal as Python *concatenates* stacks: the
previously reified stack (from the except clause) is stacked on top of
the new stack (from this raises), this leads to tracebacks "jumping
around" at the break point of the handler and is somewhat confusing.
So we want to use explicit chaining (`raise a from b`) with the
"source" providing the caught exception's original traceback and the
child providing the rest.
However since callers rely on the exception making sense, we need the
re-raised exception to be the original[0]. Copying the exception
doesn't work (see [0]), chaining an exception to itself doesn't
do anything useful, and while we could probably copy exceptions using
the pickle method[1] that's still risky.
So the most reliable option seems to be to create a new "cause"
exception, move the old traceback over to it, then re-raise the
original exception having cleared its traceback, chained to new the
cause.
[0] or a copy thereof but Odoo exceptions don't all work properly with
copy.copy and we don't want that to fail so not really an option,
we can't rely / bet on every new exception being cleanly copy-able
[1] create an "empty" instance using __new__ (or an instance of
something else onto which we re-set the __class__ in case the exctype
actually overrides __new__) then copy the __dict__
closesodoo/odoo#39709
Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>
Xavier Morel
badb95fbce