Weight annotation for block hooks. (#4058)

* Initial version that works with proper tests.

* get rid of todos and grumbles and such.

* Cleanup and fix line-width

* fix test runtime test

substrate/core/sr-primitives/src/testing.rs

@@ -145,7 +145,7 @@ pub type DigestItem = generic::DigestItem<H256>;
 pub type Digest = generic::Digest<H256>;
 
 /// Block Header
-#[derive(PartialEq, Eq, Clone, Serialize, Debug, Encode, Decode)]
+#[derive(PartialEq, Eq, Clone, Serialize, Debug, Encode, Decode, Default)]
 #[serde(rename_all = "camelCase")]
 #[serde(deny_unknown_fields)]
 pub struct Header {
@@ -198,6 +198,16 @@ impl traits::Header for Header {
 	}
 }
 
+impl Header {
+	/// A new header with the given number and default hash for all other fields.
+	pub fn new_from_number(number: <Self as traits::Header>::Number) -> Self {
+		Self {
+			number,
+			..Default::default()
+		}
+	}
+}
+
 impl<'a> Deserialize<'a> for Header {
 	fn deserialize<D: Deserializer<'a>>(de: D) -> Result<Self, D::Error> {
 		let r = <Vec<u8>>::deserialize(de)?;

substrate/core/sr-primitives/src/weights.rs

@@ -37,8 +37,9 @@
 
 #[cfg(feature = "std")]
 use serde::{Serialize, Deserialize};
+use impl_trait_for_tuples::impl_for_tuples;
 use codec::{Encode, Decode};
-use arithmetic::traits::Bounded;
+use arithmetic::traits::{Bounded, Zero};
 use crate::RuntimeDebug;
 
 /// Re-export priority as type
@@ -62,6 +63,35 @@ pub trait ClassifyDispatch<T> {
 	fn classify_dispatch(&self, target: T) -> DispatchClass;
 }
 
+/// Means of determining the weight of a block's lifecycle hooks: on_initialize, on_finalize and
+/// such.
+pub trait WeighBlock<BlockNumber> {
+	/// Return the weight of the block's on_initialize hook.
+	fn on_initialize(_: BlockNumber) -> Weight { Zero::zero() }
+	/// Return the weight of the block's on_finalize hook.
+	fn on_finalize(_: BlockNumber) -> Weight { Zero::zero() }
+}
+
+/// Maybe I can do something to remove the duplicate code here.
+#[impl_for_tuples(30)]
+impl<BlockNumber: Copy> WeighBlock<BlockNumber> for SingleModule {
+	fn on_initialize(n: BlockNumber) -> Weight {
+		let mut accumulated_weight: Weight = Zero::zero();
+		for_tuples!(
+			#( accumulated_weight = accumulated_weight.saturating_add(SingleModule::on_initialize(n)); )*
+		);
+		accumulated_weight
+	}
+
+	fn on_finalize(n: BlockNumber) -> Weight {
+		let mut accumulated_weight: Weight = Zero::zero();
+		for_tuples!(
+			#( accumulated_weight = accumulated_weight.saturating_add(SingleModule::on_finalize(n)); )*
+		);
+		accumulated_weight
+	}
+}
+
 /// A generalized group of dispatch types. This is only distinguishing normal, user-triggered transactions
 /// (`Normal`) and anything beyond which serves a higher purpose to the system (`Operational`).
 #[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
@@ -181,3 +211,10 @@ impl Default for SimpleDispatchInfo {
 		SimpleDispatchInfo::FixedNormal(10_000)
 	}
 }
+
+impl SimpleDispatchInfo {
+	/// An _additive zero_ variant of SimpleDispatchInfo.
+	pub fn zero() -> Self {
+		Self::FixedNormal(0)
+	}
+}