From ee726ed55d737aebc004214429fa18e049c71a3f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bastian=20K=C3=B6cher?= <bkchr@users.noreply.github.com>
Date: Wed, 19 May 2021 10:37:42 +0200
Subject: [PATCH] Improve `impl_opaque_keys!` (#8856)

The macro should assume less about the scope where it is being used in.
In this case it is about not assuming that the crate where the macro is
called in provides a `std` feature.
---
 substrate/primitives/runtime/src/traits.rs | 133 ++++++++++++++-------
 1 file changed, 91 insertions(+), 42 deletions(-)

diff --git a/substrate/primitives/runtime/src/traits.rs b/substrate/primitives/runtime/src/traits.rs
index 41820d8cb4..22f6cb044a 100644
--- a/substrate/primitives/runtime/src/traits.rs
+++ b/substrate/primitives/runtime/src/traits.rs
@@ -1183,31 +1183,9 @@ macro_rules! count {
 	};
 }
 
-/// Implement `OpaqueKeys` for a described struct.
-///
-/// Every field type must implement [`BoundToRuntimeAppPublic`](crate::BoundToRuntimeAppPublic).
-/// `KeyTypeIdProviders` is set to the types given as fields.
-///
-/// ```rust
-/// use sp_runtime::{
-/// 	impl_opaque_keys, KeyTypeId, BoundToRuntimeAppPublic, app_crypto::{sr25519, ed25519}
-/// };
-///
-/// pub struct KeyModule;
-/// impl BoundToRuntimeAppPublic for KeyModule { type Public = ed25519::AppPublic; }
-///
-/// pub struct KeyModule2;
-/// impl BoundToRuntimeAppPublic for KeyModule2 { type Public = sr25519::AppPublic; }
-///
-/// impl_opaque_keys! {
-/// 	pub struct Keys {
-/// 		pub key_module: KeyModule,
-/// 		pub key_module2: KeyModule2,
-/// 	}
-/// }
-/// ```
+#[doc(hidden)]
 #[macro_export]
-macro_rules! impl_opaque_keys {
+macro_rules! impl_opaque_keys_inner {
 	(
 		$( #[ $attr:meta ] )*
 		pub struct $name:ident {
@@ -1217,24 +1195,18 @@ macro_rules! impl_opaque_keys {
 			)*
 		}
 	) => {
-		$crate::paste::paste! {
-			#[cfg(feature = "std")]
-			use $crate::serde as [< __opaque_keys_serde_import__ $name >];
-			$( #[ $attr ] )*
-				#[derive(
-					Default, Clone, PartialEq, Eq,
-					$crate::codec::Encode,
-					$crate::codec::Decode,
-					$crate::RuntimeDebug,
-				)]
-			#[cfg_attr(feature = "std", derive($crate::serde::Serialize, $crate::serde::Deserialize))]
-			#[cfg_attr(feature = "std", serde(crate = "__opaque_keys_serde_import__" $name))]
-			pub struct $name {
-				$(
-					$( #[ $inner_attr ] )*
-						pub $field: <$type as $crate::BoundToRuntimeAppPublic>::Public,
-				)*
-			}
+		$( #[ $attr ] )*
+		#[derive(
+			Default, Clone, PartialEq, Eq,
+			$crate::codec::Encode,
+			$crate::codec::Decode,
+			$crate::RuntimeDebug,
+		)]
+		pub struct $name {
+			$(
+				$( #[ $inner_attr ] )*
+				pub $field: <$type as $crate::BoundToRuntimeAppPublic>::Public,
+			)*
 		}
 
 		impl $name {
@@ -1320,6 +1292,83 @@ macro_rules! impl_opaque_keys {
 	};
 }
 
+/// Implement `OpaqueKeys` for a described struct.
+///
+/// Every field type must implement [`BoundToRuntimeAppPublic`](crate::BoundToRuntimeAppPublic).
+/// `KeyTypeIdProviders` is set to the types given as fields.
+///
+/// ```rust
+/// use sp_runtime::{
+/// 	impl_opaque_keys, KeyTypeId, BoundToRuntimeAppPublic, app_crypto::{sr25519, ed25519}
+/// };
+///
+/// pub struct KeyModule;
+/// impl BoundToRuntimeAppPublic for KeyModule { type Public = ed25519::AppPublic; }
+///
+/// pub struct KeyModule2;
+/// impl BoundToRuntimeAppPublic for KeyModule2 { type Public = sr25519::AppPublic; }
+///
+/// impl_opaque_keys! {
+/// 	pub struct Keys {
+/// 		pub key_module: KeyModule,
+/// 		pub key_module2: KeyModule2,
+/// 	}
+/// }
+/// ```
+#[macro_export]
+#[cfg(feature = "std")]
+macro_rules! impl_opaque_keys {
+	{
+		$( #[ $attr:meta ] )*
+		pub struct $name:ident {
+			$(
+				$( #[ $inner_attr:meta ] )*
+				pub $field:ident: $type:ty,
+			)*
+		}
+	} => {
+		$crate::paste::paste! {
+			use $crate::serde as [< __opaque_keys_serde_import__ $name >];
+
+			$crate::impl_opaque_keys_inner! {
+				$( #[ $attr ] )*
+				#[derive($crate::serde::Serialize, $crate::serde::Deserialize)]
+				#[serde(crate = "__opaque_keys_serde_import__" $name)]
+				pub struct $name {
+					$(
+						$( #[ $inner_attr ] )*
+						pub $field: $type,
+					)*
+				}
+			}
+		}
+	}
+}
+
+#[macro_export]
+#[cfg(not(feature = "std"))]
+macro_rules! impl_opaque_keys {
+	{
+		$( #[ $attr:meta ] )*
+		pub struct $name:ident {
+			$(
+				$( #[ $inner_attr:meta ] )*
+				pub $field:ident: $type:ty,
+			)*
+		}
+	} => {
+		$crate::impl_opaque_keys_inner! {
+			$( #[ $attr ] )*
+			pub struct $name {
+				$(
+					$( #[ $inner_attr ] )*
+					pub $field: $type,
+				)*
+			}
+		}
+	}
+}
+
 /// Trait for things which can be printed from the runtime.
 pub trait Printable {
 	/// Print the object.