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// This file is part of Substrate.
// Copyright (C) 2018-2022 Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Macros that define an Event types. Events can be used to easily report changes or conditions
//! in your runtime to external entities like users, chain explorers, or dApps.
// You should have received a copy of the GNU General Public License
// along with Substrate. If not, see <http://www.gnu.org/licenses/>.
/// Implement the `Event` for a module.
///
/// # Simple Event Example:
///
/// ```rust
/// frame_support::decl_event!(
/// pub enum Event {
/// Success,
/// Failure(String),
/// }
/// );
///
/// # fn main() {}
/// ```
///
/// # Generic Event Example:
///
/// ```rust
/// trait Config {
/// type Balance;
/// type Token;
/// }
///
/// mod event1 {
/// // Event that specifies the generic parameter explicitly (`Balance`).
/// frame_support::decl_event!(
/// pub enum Event<T> where Balance = <T as super::Config>::Balance {
/// Message(Balance),
/// }
/// );
/// }
///
/// mod event2 {
/// // Event that uses the generic parameter `Balance`.
/// // If no name for the generic parameter is specified explicitly,
/// // the name will be taken from the type name of the trait.
/// frame_support::decl_event!(
/// pub enum Event<T> where <T as super::Config>::Balance {
/// Message(Balance),
/// }
/// );
/// }
///
/// mod event3 {
/// // And we even support declaring multiple generic parameters!
/// frame_support::decl_event!(
/// pub enum Event<T> where <T as super::Config>::Balance, <T as super::Config>::Token {
/// Message(Balance, Token),
/// }
/// );
/// }
///
/// # fn main() {}
/// ```
///
/// The syntax for generic events requires the `where`.
///
/// # Generic Event with Instance Example:
///
/// ```rust
/// # struct DefaultInstance;
/// # trait Instance {}
/// # impl Instance for DefaultInstance {}
/// trait Config<I: Instance=DefaultInstance> {
/// type Balance;
/// type Token;
/// }
///
/// // For module with instances, DefaultInstance is optional
/// frame_support::decl_event!(
/// pub enum Event<T, I: Instance = DefaultInstance> where
/// <T as Config>::Balance,
/// <T as Config>::Token
/// {
/// Message(Balance, Token),
/// }
/// );
/// # fn main() {}
/// ```
#[macro_export]
macro_rules! decl_event {
(
$(#[$attr:meta])*
pub enum Event<$evt_generic_param:ident $(, $instance:ident $(: $instantiable:ident)? $( = $event_default_instance:path)? )?> where
$( $tt:tt )*
) => {
$crate::__decl_generic_event!(
$( #[ $attr ] )*;
$evt_generic_param;
$($instance $( = $event_default_instance)? )?;
{ $( $tt )* };
);
};
(
$(#[$attr:meta])*
pub enum Event {
$(
$events:tt
)*
}
) => {
// Workaround for https://github.com/rust-lang/rust/issues/26925 . Remove when sorted.
#[derive(
Clone, PartialEq, Eq,
$crate::codec::Encode,
$crate::codec::Decode,
$crate::scale_info::TypeInfo,
$crate::RuntimeDebug,
)]
#[scale_info(capture_docs = "always")]
/// Events for this module.
///
$(#[$attr])*
pub enum Event {
$(
$events
)*
}
impl From<Event> for () {
fn from(_: Event) -> () { () }
}
}
}
#[macro_export]
#[doc(hidden)]
// This parsing to retrieve last ident on unnamed generic could be improved.
// but user can still name it if the parsing fails. And improving parsing seems difficult.
macro_rules! __decl_generic_event {
(
$(#[$attr:meta])*;
$event_generic_param:ident;
$($instance:ident $( = $event_default_instance:path)? )?;
{ $( $tt:tt )* };
) => {
$crate::__decl_generic_event!(@format_generic
$( #[ $attr ] )*;
$event_generic_param;
$($instance $( = $event_default_instance)? )?;
{ $( $tt )* };
{};
);
};
// Finish formatting on an unnamed one
(@format_generic
$(#[$attr:meta])*;
$event_generic_param:ident;
$($instance:ident $( = $event_default_instance:path)? )?;
{ <$generic:ident as $trait:path>::$trait_type:ident $(,)? { $( $events:tt )* } };
{$( $parsed:tt)*};
) => {
$crate::__decl_generic_event!(@generate
$( #[ $attr ] )*;
$event_generic_param;
$($instance $( = $event_default_instance)? )?;
{ $($events)* };
{ $($parsed)*, $trait_type = <$generic as $trait>::$trait_type };
);
};
// Finish formatting on a named one
(@format_generic
$(#[$attr:meta])*;
$event_generic_param:ident;
$($instance:ident $( = $event_default_instance:path)? )?;
{ $generic_rename:ident = $generic_type:ty $(,)? { $( $events:tt )* } };
{ $($parsed:tt)* };
) => {
$crate::__decl_generic_event!(@generate
$(#[$attr])*;
$event_generic_param;
$($instance $( = $event_default_instance)? )?;
{ $($events)* };
{ $($parsed)*, $generic_rename = $generic_type };
);
};
// Parse named
(@format_generic
$(#[$attr:meta])*;
$event_generic_param:ident;
$($instance:ident $( = $event_default_instance:path)? )?;
{ $generic_rename:ident = $generic_type:ty, $($rest:tt)* };
{$( $parsed:tt)*};
) => {
$crate::__decl_generic_event!(@format_generic
$( #[ $attr ] )*;
$event_generic_param;
$( $instance $( = $event_default_instance)? )?;
{ $($rest)* };
{ $($parsed)*, $generic_rename = $generic_type };
);
};
// Parse unnamed
(@format_generic
$(#[$attr:meta])*;
$event_generic_param:ident;
$($instance:ident $( = $event_default_instance:path)? )?;
{ <$generic:ident as $trait:path>::$trait_type:ident, $($rest:tt)* };
{$($parsed:tt)*};
) => {
$crate::__decl_generic_event!(@format_generic
$( #[ $attr ] )*;
$event_generic_param;
$($instance $( = $event_default_instance)? )?;
{ $($rest)* };
{ $($parsed)*, $trait_type = <$generic as $trait>::$trait_type };
);
};
// Unnamed type can't be parsed
(@format_generic
$(#[$attr:meta])*;
$event_generic_param:ident;
$($instance:ident $( = $event_default_instance:path)? )?;
{ $generic_type:ty, $($rest:tt)* };
{ $($parsed:tt)* };
) => {
$crate::__decl_generic_event!(@cannot_parse $generic_type);
};
// Final unnamed type can't be parsed
(@format_generic
$(#[$attr:meta])*;
$event_generic_param:ident;
$($instance:ident $( = $event_default_instance:path)? )?;
{ $generic_type:ty { $( $events:tt )* } };
{$( $parsed:tt)*};
) => {
$crate::__decl_generic_event!(@cannot_parse $generic_type);
};
(@generate
$(#[$attr:meta])*;
$event_generic_param:ident;
$($instance:ident $( = $event_default_instance:path)? )?;
{ $( $events:tt )* };
{ ,$( $generic_param:ident = $generic_type:ty ),* };
) => {
/// [`RawEvent`] specialized for the configuration [`Config`]
///
/// [`RawEvent`]: enum.RawEvent.html
/// [`Config`]: trait.Config.html
pub type Event<$event_generic_param $(, $instance $( = $event_default_instance)? )?> = RawEvent<$( $generic_type ),* $(, $instance)? >;
#[derive(
Clone, PartialEq, Eq,
$crate::codec::Encode,
$crate::codec::Decode,
$crate::scale_info::TypeInfo,
$crate::RuntimeDebug,
)]
#[scale_info(capture_docs = "always")]
/// Events for this module.
///
$(#[$attr])*
pub enum RawEvent<$( $generic_param ),* $(, $instance)? > {
$(
$events
)*
$(
#[doc(hidden)]
#[codec(skip)]
PhantomData($crate::sp_std::marker::PhantomData<$instance>),
)?
}
impl<$( $generic_param ),* $(, $instance)? > From<RawEvent<$( $generic_param ),* $(, $instance)?>> for () {
fn from(_: RawEvent<$( $generic_param ),* $(, $instance)?>) -> () { () }
}
};
(@cannot_parse $ty:ty) => {
compile_error!(concat!("The type `", stringify!($ty), "` can't be parsed as an unnamed one, please name it `Name = ", stringify!($ty), "`"));
}
}