1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
// This file is part of Substrate.

// Copyright (C) 2019-2020 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.

//! Macro for declaring a module error.

#[doc(hidden)]
pub use sp_runtime::traits::{LookupError, BadOrigin};
#[doc(hidden)]
pub use frame_metadata::{ModuleErrorMetadata, ErrorMetadata, DecodeDifferent};

/// Declare an error type for a runtime module.
///
/// `decl_error!` supports only variants that do not hold any data. The dispatchable
/// functions return [`DispatchResult`](sp_runtime::DispatchResult). The error type
/// implements `From<ErrorType> for DispatchResult` to make the error type usable as error
/// in the dispatchable functions.
///
/// It is required that the error type is registered in `decl_module!` to make the error
/// exported in the metadata.
///
/// # Usage
///
/// ```
/// # use frame_support::{decl_error, decl_module};
/// #
/// decl_error! {
///     /// Errors that can occur in my module.
///     pub enum MyError for Module<T: Trait> {
///         /// Hey this is an error message that indicates bla.
///         MyCoolErrorMessage,
///         /// You are just not cool enough for my module!
///         YouAreNotCoolEnough,
///     }
/// }
///
/// # use frame_system::Trait;
///
/// // You need to register the error type in `decl_module!` as well to make the error
/// // exported in the metadata.
///
/// decl_module! {
///     pub struct Module<T: Trait> for enum Call where origin: T::Origin {
///         type Error = MyError<T>;
///
///         #[weight = 0]
///         fn do_something(origin) -> frame_support::dispatch::DispatchResult {
///             Err(MyError::<T>::YouAreNotCoolEnough.into())
///         }
///     }
/// }
///
/// # fn main() {}
/// ```
///
/// For instantiable modules you also need to give the instance generic type and bound to the
/// error declaration.
#[macro_export]
macro_rules! decl_error {
	(
		$(#[$attr:meta])*
		pub enum $error:ident
			for $module:ident<
				$generic:ident: $trait:path
				$(, $inst_generic:ident: $instance:path)?
			>
			$( where $( $where_ty:ty: $where_bound:path ),* $(,)? )?
		{
			$(
				$( #[doc = $doc_attr:tt] )*
				$name:ident
			),*
			$(,)?
		}
	) => {
		$(#[$attr])*
		pub enum $error<$generic: $trait $(, $inst_generic: $instance)?>
		$( where $( $where_ty: $where_bound ),* )?
		{
			#[doc(hidden)]
			__Ignore(
				$crate::sp_std::marker::PhantomData<($generic, $( $inst_generic)?)>,
				$crate::Never,
			),
			$(
				$( #[doc = $doc_attr] )*
				$name
			),*
		}

		impl<$generic: $trait $(, $inst_generic: $instance)?> $crate::sp_std::fmt::Debug
			for $error<$generic $(, $inst_generic)?>
		$( where $( $where_ty: $where_bound ),* )?
		{
			fn fmt(&self, f: &mut $crate::sp_std::fmt::Formatter<'_>) -> $crate::sp_std::fmt::Result {
				f.write_str(self.as_str())
			}
		}

		impl<$generic: $trait $(, $inst_generic: $instance)?> $error<$generic $(, $inst_generic)?>
		$( where $( $where_ty: $where_bound ),* )?
		{
			fn as_u8(&self) -> u8 {
				$crate::decl_error! {
					@GENERATE_AS_U8
					self
					$error
					{}
					0,
					$( $name ),*
				}
			}

			fn as_str(&self) -> &'static str {
				match self {
					Self::__Ignore(_, _) => unreachable!("`__Ignore` can never be constructed"),
					$(
						$error::$name => stringify!($name),
					)*
				}
			}
		}

		impl<$generic: $trait $(, $inst_generic: $instance)?> From<$error<$generic $(, $inst_generic)?>>
			for &'static str
		$( where $( $where_ty: $where_bound ),* )?
		{
			fn from(err: $error<$generic $(, $inst_generic)?>) -> &'static str {
				err.as_str()
			}
		}

		impl<$generic: $trait $(, $inst_generic: $instance)?> From<$error<$generic $(, $inst_generic)?>>
			for $crate::sp_runtime::DispatchError
		$( where $( $where_ty: $where_bound ),* )?
		{
			fn from(err: $error<$generic $(, $inst_generic)?>) -> Self {
				let index = <$generic::PalletInfo as $crate::traits::PalletInfo>
					::index::<$module<$generic $(, $inst_generic)?>>()
					.expect("Every active module has an index in the runtime; qed") as u8;

				$crate::sp_runtime::DispatchError::Module {
					index,
					error: err.as_u8(),
					message: Some(err.as_str()),
				}
			}
		}

		impl<$generic: $trait $(, $inst_generic: $instance)?> $crate::error::ModuleErrorMetadata
			for $error<$generic $(, $inst_generic)?>
		$( where $( $where_ty: $where_bound ),* )?
		{
			fn metadata() -> &'static [$crate::error::ErrorMetadata] {
				&[
					$(
						$crate::error::ErrorMetadata {
							name: $crate::error::DecodeDifferent::Encode(stringify!($name)),
							documentation: $crate::error::DecodeDifferent::Encode(&[
								$( $doc_attr ),*
							]),
						}
					),*
				]
			}
		}
	};
	(@GENERATE_AS_U8
		$self:ident
		$error:ident
		{ $( $generated:tt )* }
		$index:expr,
		$name:ident
		$( , $rest:ident )*
	) => {
		$crate::decl_error! {
			@GENERATE_AS_U8
			$self
			$error
			{
				$( $generated )*
				$error::$name => $index,
			}
			$index + 1,
			$( $rest ),*
		}
	};
	(@GENERATE_AS_U8
		$self:ident
		$error:ident
		{ $( $generated:tt )* }
		$index:expr,
	) => {
		match $self {
			$error::__Ignore(_, _) => unreachable!("`__Ignore` can never be constructed"),
			$( $generated )*
		}
	}
}