Tasks: general system for recognizing and executing service work

[sam0x17]

polkadot-sdk version of original tasks PR located here: paritytech/substrate#14329

Fixes #206

Status

• Generic Task trait
• RuntimeTask aggregated enum, compatible with construct_runtime!
• Casting between Task and RuntimeTask without needing dyn or Box
• Tasks Example pallet
• Runtime tests for Tasks example pallet
• Parsing for task-related macros
• Retrofit parsing to make macros optional
• Expansion for task-related macros
• Adds support for args in tasks
• Retrofit tasks example pallet to use macros instead of manual syntax
• Weights
• Cleanup
• UI tests
• Docs

Target Syntax

Adapted from #206 (comment)

// NOTE: this enum is optional and is auto-generated by the other macros if not present
#[pallet::task]
pub enum Task<T: Config> {
    AddNumberIntoTotal {
        i: u32,
    }
}

/// Some running total.
#[pallet::storage]
pub(super) type Total<T: Config<I>, I: 'static = ()> =
StorageValue<_, (u32, u32), ValueQuery>;

/// Numbers to be added into the total.
#[pallet::storage]
pub(super) type Numbers<T: Config<I>, I: 'static = ()> =
StorageMap<_, Twox64Concat, u32, u32, OptionQuery>;

#[pallet::tasks_experimental]
impl<T: Config<I>, I: 'static> Pallet<T, I> {
	/// Add a pair of numbers into the totals and remove them.
	#[pallet::task_list(Numbers::<T, I>::iter_keys())]
	#[pallet::task_condition(|i| Numbers::<T, I>::contains_key(i))]
	#[pallet::task_index(0)]
	pub fn add_number_into_total(i: u32) -> DispatchResult {
		let v = Numbers::<T, I>::take(i).ok_or(Error::<T, I>::NotFound)?;
		Total::<T, I>::mutate(|(total_keys, total_values)| {
			*total_keys += i;
			*total_values += v;
		});
		Ok(())
	}
}

[sam0x17]

btw this branch is going to get force-pushed over later today -- my version that actually has the correct rebase with polkadot-sdk is local right now. This one had some issues.

[sam0x17]

remaining compile issue:

the trait bound `RuntimeEvent: From<tasks_example::Event<Runtime>>` is not satisfied

is this because I'm not generating a From impl that I should be generating in my RuntimeTask macro expansion, or do I have something else wrong somewhere else?

I just find it strange that it suddenly needs this because I didn't need this impl at all on the substrate version of this branch.

[KiChjang]

Did you forget to include the tasks_example pallet in your construct_runtime?

[sam0x17]

Did you forget to include the tasks_example pallet in your construct_runtime?

lmao thank you yes I think this was one of the lines the patch file misses

[sam0x17]

Did you forget to include the tasks_example pallet in your construct_runtime?

oh yeah and then the weird follow-up to that that I remember fixing for substrate but now forget how I fixed:

after adding TasksExample: tasks_example to construct_runtime, I then get this error on the construct_runtime!:

  error: expected one of: `Pallet`, `Call`, `Storage`, `Event`, `Error`, `Config`, `Origin`, `Inherent`, `ValidateUnsigned`, `FreezeReason`, `HoldReason`, `Task`, `LockId`, `SlashReason`

🤔

(now pushed up on this branch)

[gupnik]

Did you forget to include the tasks_example pallet in your construct_runtime?

oh yeah and then the weird follow-up to that that I remember fixing for substrate but now forget how I fixed:

after adding TasksExample: tasks_example to construct_runtime, I then get this error on the construct_runtime!:

  error: expected one of: `Pallet`, `Call`, `Storage`, `Event`, `Error`, `Config`, `Origin`, `Inherent`, `ValidateUnsigned`, `FreezeReason`, `HoldReason`, `Task`, `LockId`, `SlashReason`

🤔

(now pushed up on this branch)

@sam0x17 It seems that task_part becomes None if a pallet doesn't have any tasks. In that case, we probably want to set it to quote::quote!() inside tt_default_parts. Pushed the fix.

[sam0x17]

new one @KiChjang / @gupnik:

edit: resolved

On current version of the branch, when compiling substrate/bin/node/runtime, I currently get:

     Compiling kitchensink-runtime v3.0.0-dev (/home/sam/workspace/polkadot-sdk/substrate/bin/node/runtime)
  error[E0532]: expected tuple struct or tuple variant, found type alias `TasksExample`
      --> /home/sam/workspace/polkadot-sdk/substrate/bin/node/runtime/src/lib.rs:2096:3
       |
  2096 |         TasksExample: tasks_example,
       |         ^^^^^^^^^^^^
       |

All I've changed is I've added proper impls for the RuntimeTask methods including enumerate(), and previously this line was fine. Is there something obvious I'm missing?

[sam0x17]

🎉

[louismerlin]

Approving for bot, SRLabs will review this in the future, PR is in pipeline

[Polkadot-Forum]

This pull request has been mentioned on Polkadot Forum. There might be relevant details there:

https://forum.polkadot.network/t/polkadot-release-analysis-v1-6-0/5855/1