allow to write pre and post runtime upgrade in pallet macro

[gui1117]

I removed the default implementation of pre_upgrade and post_upgrade on OnRuntimeUpgrade.
Otherwise if node-runtime forget to activate the my-pallet/try-runtime then the pre_upgrade and post_upgrade of the pallet would simply be ignored without warning. Instead now it fails to compile saying pre_upgrade and post_upgrade needs to be implemented.

But the error is:

error[E0046]: not all trait items implemented, missing: `pre_upgrade`, `post_upgrade`
   --> frame/system/src/lib.rs:262:12
    |
262 |     #[pallet::hooks]
    |               ^^^^^ missing `pre_upgrade`, `post_upgrade` in implementation
    |
    = help: implement the missing item: `fn pre_upgrade() -> Result<(), &'static str> { todo!() }`
    = help: implement the missing item: `fn post_upgrade() -> Result<(), &'static str> { todo!() }`

So it is not super explicit (but still better than silently ignore it).

NOTE: the PR doesn't add the feature to decl_module, we can do in another one if we want.

[gui1117]

I also added std here in order to be able to compile the crate with try-runtime and std.
(cargo check -p node-runtime --features try-runtime)

Otherwise it fails.

[bkchr]

The problem with that is that Cargo currently doesn't support optional dependencies and features.

Not sure how this works 🤷

[gui1117]

AFAICT this will pull frame-try-runtime crate everytime std is activated, which is not what we want, but is not bothering too much either.

EDIT: and we do same for frame-benchmarking.

[kianenigma]

I think given the same situation with benchmark, let's move on and let it be, but a refactor issue for it will be appreciated. Maybe we can do it nicer someday.

[gui1117]

yes I think there is plan to support it with something like "frame-try-runtime?/std"

Ok then I'll merge and open an issue: #8202

[bkchr]

Besides the one comment it looks okay.

[bkchr]

The problem with that is that Cargo currently doesn't support optional dependencies and features.

Not sure how this works 🤷