Because the `savepoint` and `clear` calls are nested inside the
`assertRaises` context, if one of them happens to throw *the exception
we're looking for* the interpreter will jump back to the `with`, the
`assertRaises` will swallow the exception (and count it as a success)
and the function will end having not gone through a `yield`.
This is rather frustrating to debug as it's easy to forget that a
`with` is a control flow structure, leading to a seemingly impossible
error.
We can fix this by initializing and `__enter__`-ing the savepoint
first, but doing this by hand is a bit iffy and not really
future-proof as the addition of more fallible steps during the
initialization phase of `_assertRaises` could lead to the savepoint
not being properly disposed of. Furthermore once in the scope of the
"actual" assertRaises we want the savepoint to unwind first (otherwise
the savepoint won't be rolled back when the exception *we are
expecting* gets raised).
As it turns out `ExitStack` offers the solution to our woes though
it's a bit tricky at first glance: while modifying the cleanup queue
in-place is haram, `pop_all` allows moving cleanup callbacks from one
queue to the next.
This means we can first add the savepoint to one stack and get its
errors (if any) correctly reported, cover the rest of the
initialization, then move the savepoint from one stack to an other, in
order to correctly order the coverage of the `yield` (and the userland
code).
closesodoo/odoo#87733
X-original-commit: b1cd4e4e3c918b4b08d27b30b1017fc898d4b08a
Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>
Xavier Morel
6c3bbdbef8