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>
Fixes https://github.com/paritytech/polkadot-sdk/issues/1725
This PR adds the following changes:
1. An attribute `pallet::feeless_if` that can be optionally attached to
a call like so:
```rust
#[pallet::feeless_if(|_origin: &OriginFor<T>, something: &u32| -> bool {
*something == 0
})]
pub fn do_something(origin: OriginFor<T>, something: u32) -> DispatchResult {
....
}
```
The closure passed accepts references to arguments as specified in the
call fn. It returns a boolean that denotes the conditions required for
this call to be "feeless".
2. A signed extension `SkipCheckIfFeeless<T: SignedExtension>` that
wraps a transaction payment processor such as
`pallet_transaction_payment::ChargeTransactionPayment`. It checks for
all calls annotated with `pallet::feeless_if` to see if the conditions
are met. If so, the wrapped signed extension is not called, essentially
making the call feeless.
In order to use this, you can simply replace your existing signed
extension that manages transaction payment like so:
```diff
- pallet_transaction_payment::ChargeTransactionPayment<Runtime>,
+ pallet_skip_feeless_payment::SkipCheckIfFeeless<
+ Runtime,
+ pallet_transaction_payment::ChargeTransactionPayment<Runtime>,
+ >,
```
### Todo
- [x] Tests
- [x] Docs
- [x] Prdoc
---------
Co-authored-by: Nikhil Gupta <>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>
closes https://github.com/paritytech/polkadot-sdk/issues/1882
## Breaking Changes
This PR introduces a new item to `pallet_balances::Config`:
```diff
trait Config {
++ type RuntimeFreezeReasons;
}
```
This value is only used to check it against `type MaxFreeze`. A similar
check has been added for `MaxHolds` against `RuntimeHoldReasons`, which
is already given to `pallet_balances`.
In all contexts, you should pass the real `RuntimeFreezeReasons`
generated by `construct_runtime` to `type RuntimeFreezeReasons`. Passing
`()` would also work, but it would imply that the runtime uses no
freezes at all.
---------
Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Moving a few pallets to the latest and greatest `derive_impl` to give it
a try.
Part of #171
---------
Co-authored-by: Adrian Catangiu <adrian@parity.io>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>
gupnik