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[frame] #[pallet::composite_enum] improved variant count handling + removed pallet_balances's MaxHolds config (#2657)

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I started this investigation/issue based on @liamaharon question
[here](https://github.com/paritytech/polkadot-sdk/pull/1801#discussion_r1410452499).

## Problem

The `pallet_balances` integrity test should correctly detect that the
runtime has correct distinct `HoldReasons` variant count. I assume the
same situation exists for RuntimeFreezeReason.

It is not a critical problem, if we set `MaxHolds` with a sufficiently
large value, everything should be ok. However, in this case, the
integrity_test check becomes less useful.

**Situation for "any" runtime:**
- `HoldReason` enums from different pallets:
```rust
        /// from pallet_nis
        #[pallet::composite_enum]
	pub enum HoldReason {
		NftReceipt,
	}

        /// from pallet_preimage
        #[pallet::composite_enum]
	pub enum HoldReason {
		Preimage,
	}

        // from pallet_state-trie-migration
        #[pallet::composite_enum]
	pub enum HoldReason {
		SlashForContinueMigrate,
		SlashForMigrateCustomTop,
		SlashForMigrateCustomChild,
	}
```

- generated `RuntimeHoldReason` enum looks like:
```rust
pub enum RuntimeHoldReason {

    #[codec(index = 32u8)]
    Preimage(pallet_preimage::HoldReason),

    #[codec(index = 38u8)]
    Nis(pallet_nis::HoldReason),

    #[codec(index = 42u8)]
    StateTrieMigration(pallet_state_trie_migration::HoldReason),
}
```

- composite enum `RuntimeHoldReason` variant count is detected as `3`
- we set `type MaxHolds = ConstU32<3>`
- `pallet_balances::integrity_test` is ok with `3`(at least 3)

However, the real problem can occur in a live runtime where some
functionality might stop working. This is due to a total of 5 distinct
hold reasons (for pallets with multi-instance support, it is even more),
and not all of them can be used because of an incorrect `MaxHolds`,
which is deemed acceptable according to the `integrity_test`:
  ```
  // pseudo-code - if we try to call all of these:

T::Currency::hold(&pallet_nis::HoldReason::NftReceipt.into(),
&nft_owner, deposit)?;
T::Currency::hold(&pallet_preimage::HoldReason::Preimage.into(),
&nft_owner, deposit)?;

T::Currency::hold(&pallet_state_trie_migration::HoldReason::SlashForContinueMigrate.into(),
&nft_owner, deposit)?;

  // With `type MaxHolds = ConstU32<3>` these two will fail

T::Currency::hold(&pallet_state_trie_migration::HoldReason::SlashForMigrateCustomTop.into(),
&nft_owner, deposit)?;

T::Currency::hold(&pallet_state_trie_migration::HoldReason::SlashForMigrateCustomChild.into(),
&nft_owner, deposit)?;
  ```  


## Solutions

A macro `#[pallet::*]` expansion is extended of `VariantCount`
implementation for the `#[pallet::composite_enum]` enum type. This
expansion generates the `VariantCount` implementation for pallets'
`HoldReason`, `FreezeReason`, `LockId`, and `SlashReason`. Enum variants
must be plain enum values without fields to ensure a deterministic
count.

The composite runtime enum, `RuntimeHoldReason` and
`RuntimeFreezeReason`, now sets `VariantCount::VARIANT_COUNT` as the sum
of pallets' enum `VariantCount::VARIANT_COUNT`:
```rust
#[frame_support::pallet(dev_mode)]
mod module_single_instance {

	#[pallet::composite_enum]
	pub enum HoldReason {
		ModuleSingleInstanceReason1,
		ModuleSingleInstanceReason2,
	}
...
}

#[frame_support::pallet(dev_mode)]
mod module_multi_instance {

	#[pallet::composite_enum]
	pub enum HoldReason<I: 'static = ()> {
		ModuleMultiInstanceReason1,
		ModuleMultiInstanceReason2,
		ModuleMultiInstanceReason3,
	}
...
}


impl self::sp_api_hidden_includes_construct_runtime::hidden_include::traits::VariantCount
    for RuntimeHoldReason
{
    const VARIANT_COUNT: u32 = 0
        + module_single_instance::HoldReason::VARIANT_COUNT
        + module_multi_instance::HoldReason::<module_multi_instance::Instance1>::VARIANT_COUNT
        + module_multi_instance::HoldReason::<module_multi_instance::Instance2>::VARIANT_COUNT
        + module_multi_instance::HoldReason::<module_multi_instance::Instance3>::VARIANT_COUNT;
}
```

In addition, `MaxHolds` is removed (as suggested
[here](https://github.com/paritytech/polkadot-sdk/pull/2657#discussion_r1443324573))
from `pallet_balances`, and its `Holds` are now bounded to
`RuntimeHoldReason::VARIANT_COUNT`. Therefore, there is no need to let
the runtime specify `MaxHolds`.


## For reviewers

Relevant changes can be found here:
- `substrate/frame/support/procedural/src/lib.rs` 
-  `substrate/frame/support/procedural/src/pallet/parse/composite.rs`
-  `substrate/frame/support/procedural/src/pallet/expand/composite.rs`
-
`substrate/frame/support/procedural/src/construct_runtime/expand/composite_helper.rs`
-
`substrate/frame/support/procedural/src/construct_runtime/expand/hold_reason.rs`
-
`substrate/frame/support/procedural/src/construct_runtime/expand/freeze_reason.rs`
- `substrate/frame/support/src/traits/misc.rs`

And the rest of the files is just about removed `MaxHolds` from
`pallet_balances`

## Next steps

Do the same for `MaxFreezes`
https://github.com/paritytech/polkadot-sdk/issues/2997.

---------

Co-authored-by: command-bot <>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Dónal Murray <donal.murray@parity.io>
Co-authored-by: gupnik <nikhilgupta.iitk@gmail.com>
This commit is contained in:
Branislav Kontur
2024-01-31 07:19:16 +01:00
committed by GitHub
parent cc4805b51e
commit bb8ddc46c1
118 changed files with 610 additions and 315 deletions
Download Patch File Download Diff File Expand all files Collapse all files
substrate/frame/balances/src/lib.rs
+6 -15
View File
@@ -206,7 +206,7 @@ pub mod pallet {
use super::*;
use frame_support::{
pallet_prelude::*,
traits::{fungible::Credit, tokens::Precision, VariantCount},
traits::{fungible::Credit, tokens::Precision, VariantCount, VariantCountOf},
};
use frame_system::pallet_prelude::*;
@@ -242,7 +242,6 @@ pub mod pallet {
type MaxLocks = ConstU32<100>;
type MaxReserves = ConstU32<100>;
type MaxFreezes = ConstU32<100>;
type MaxHolds = ConstU32<100>;
type WeightInfo = ();
}
@@ -316,10 +315,6 @@ pub mod pallet {
#[pallet::constant]
type MaxReserves: Get<u32>;
/// The maximum number of holds that can exist on an account at any time.
#[pallet::constant]
type MaxHolds: Get<u32>;
/// The maximum number of individual freeze locks that can exist on an account at any time.
#[pallet::constant]
type MaxFreezes: Get<u32>;
@@ -407,7 +402,7 @@ pub mod pallet {
DeadAccount,
/// Number of named reserves exceed `MaxReserves`.
TooManyReserves,
/// Number of holds exceed `MaxHolds`.
/// Number of holds exceed `VariantCountOf<T::RuntimeHoldReason>`.
TooManyHolds,
/// Number of freezes exceed `MaxFreezes`.
TooManyFreezes,
@@ -487,7 +482,10 @@ pub mod pallet {
_,
Blake2_128Concat,
T::AccountId,
BoundedVec<IdAmount<T::RuntimeHoldReason, T::Balance>, T::MaxHolds>,
BoundedVec<
IdAmount<T::RuntimeHoldReason, T::Balance>,
VariantCountOf<T::RuntimeHoldReason>,
>,
ValueQuery,
>;
@@ -556,13 +554,6 @@ pub mod pallet {
"The existential deposit must be greater than zero!"
);
assert!(
T::MaxHolds::get() >= <T::RuntimeHoldReason as VariantCount>::VARIANT_COUNT,
"MaxHolds should be greater than or equal to the number of hold reasons: {} < {}",
T::MaxHolds::get(),
<T::RuntimeHoldReason as VariantCount>::VARIANT_COUNT
);
assert!(
T::MaxFreezes::get() >= <T::RuntimeFreezeReason as VariantCount>::VARIANT_COUNT,
"MaxFreezes should be greater than or equal to the number of freeze reasons: {} < {}",
substrate/frame/balances/src/tests/mod.rs
-1
View File
@@ -142,7 +142,6 @@ impl Config for Test {
type RuntimeFreezeReason = RuntimeFreezeReason;
type FreezeIdentifier = TestId;
type MaxFreezes = ConstU32<2>;
type MaxHolds = ConstU32<3>;
}
#[derive(Clone)]