So this bug is kinda funky. The code path is basically "if we weren't passed an
instance of the class we compose to, and we have a converter, call that".
Ignoring the hash case for a moment, everything after that was roughly intended
to be the "else" clause, meaning that we are expected to have an instance of
the class we compose to. Really, we should be blowing up in that case, as we
can give a much better error message than what they user will likely get (e.g.
`NameError: No method first for String` or something). Still, Ruby is duck
typed, so if the object you're assigning responds to the same methods as the
type you compose to, knock yourself out.
The hash case was added in 36e9be8 to remove a bunch of special cased code from
multiparameter assignment. I wrongly assumed that the only time we'd get a hash
there is in that case. Multiparameter assignment will construct a very specific
hash though, where the keys are integers, and we will have a set of keys
covering `1..part.size` exactly. I'm pretty sure this could actually be passed
around as an array, but that's a different story. Really I should convert this
to something like `class MultiParameterAssignment < Hash; end`, which I might
do soon. However for a change that I'm willing to backport to 4-2-stable, this
is what I want to go with for the time being.
Fixes#25978
Since 434df00 week durations are no longer converted to days. This means
we need to add :weeks to the parts that ActiveSupport::TimeWithZone will
consider being of variable duration to take account of DST transitions.
Fixes#26039.
The coder that Psych passes in has a `tag` method we can use to detect
which serialization format we're reviving for. Use it and make it clearer
alongside the `load_tags` fiddling.
If we were to serialize an `ActionController::Parameters` on Psych 2.0.8, we'd get:
```yaml
--- !ruby/hash:ActionController::Parameters
key: :value
```
Because 2.0.8 didn't store instance variables, while 2.0.9 did:
8f84ad0fc7
That, coupled with 2.0.8 calling `new` instead of `allocate` meant parameters was
deserialized just fine:
af308f8307
However, if users have 2.0.8 serialized parameters, then upgrade to Psych 2.0.9+ and
Rails 5, it would start to blow up because `initialize` will never be called, and thus
`@parameters` will never be assigned. Hello, `NoMethodErrors` on `NilClass`! :)
To fix this we register another variant of the previous serialization format and take
it into account in `init_with`.
I've tested this in our app and previously raising code now deserializes like a champ.
I'm unsure how to test this in our suite because we use Psych 2.0.8 and don't know how
to make us use 2.0.9+ for just one test.
By changing ActionController::Parameter's superclass, Rails 5 also changed
the YAML serialization format.
Since YAML doesn't know how to handle parameters it would fallback to its
routine for the superclass, which in Rails 4.2 was Hash while just Object
in Rails 5. As evident in the tags YAML would spit out:
4.2: !ruby/hash-with-ivars:ActionController::Parameters
5.0: !ruby/object:ActionController::Parameters
Thus when loading parameters YAML from 4.2 in Rails 5, it would parse a
hash dump as it would an Object class.
To fix this we have to provide our own `init_with` to be aware of the past
format as well as the new one. Then we add a `load_tags` mapping, such that
when the YAML parser sees `!ruby/hash-with-ivars:ActionController::Parameters`,
it knows to call our `init_with` function and not try to instantiate it as
a normal hash subclass.
This commit suppressed
`warning: instance variable @session_store not initialized`.
e5a6f7ee9e951dbe0e4e9ea2c0743b4dfb135c57 introduced these
warnings.
