Remove requirement on Hash = H256, make Proposer return StorageChanges and Proof (#3860)

* Extend `Proposer` to optionally generate a proof of the proposal

* Something

* Refactor sr-api to not depend on client anymore

* Fix benches

* Apply suggestions from code review

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Apply suggestions from code review

* Introduce new `into_storage_changes` function

* Switch to runtime api for `execute_block` and don't require `H256`
anywhere in the code

* Put the `StorageChanges` into the `Proposal`

* Move the runtime api error to its own trait

* Adds `StorageTransactionCache` to the runtime api

This requires that we add `type NodeBlock = ` to the
`impl_runtime_apis!` macro to work around some bugs in rustc :(

* Remove `type NodeBlock` and switch to a "better" hack

* Start using the transaction cache from the runtime api

* Make it compile

* Move `InMemory` to its own file

* Make all tests work again

* Return block, storage_changes and proof from Blockbuilder::bake()

* Make sure that we use/set `storage_changes` when possible

* Add test

* Fix deadlock

* Remove accidentally added folders

* Introduce `RecordProof` as argument type to be more explicit

* Update client/src/client.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Update primitives/state-machine/src/ext.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Integrates review feedback

* Remove `unsafe` usage

* Update client/block-builder/src/lib.rs

Co-Authored-By: Benjamin Kampmann <ben@gnunicorn.org>

* Update client/src/call_executor.rs

* Bump versions

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>
Co-authored-by: Benjamin Kampmann <ben.kampmann@googlemail.com>

substrate/primitives/consensus/common/src/lib.rs

@@ -31,7 +31,9 @@
 use std::sync::Arc;
 use std::time::Duration;
 
-use sp_runtime::{traits::{Block as BlockT, DigestFor}, generic::BlockId};
+use sp_runtime::{
+	generic::BlockId, traits::{Block as BlockT, DigestFor, NumberFor, HasherFor},
+};
 use futures::prelude::*;
 pub use sp_inherents::InherentData;
 
@@ -48,10 +50,11 @@ const MAX_BLOCK_SIZE: usize = 4 * 1024 * 1024 + 512;
 
 pub use self::error::Error;
 pub use block_import::{
-	BlockImport, BlockOrigin, ForkChoiceStrategy, ImportedAux, BlockImportParams, BlockCheckParams, ImportResult,
-	JustificationImport, FinalityProofImport,
+	BlockImport, BlockOrigin, ForkChoiceStrategy, ImportedAux, BlockImportParams, BlockCheckParams,
+	ImportResult, JustificationImport, FinalityProofImport,
 };
 pub use select_chain::SelectChain;
+pub use sp_state_machine::Backend as StateBackend;
 
 /// Block status.
 #[derive(Debug, PartialEq, Eq)]
@@ -71,14 +74,56 @@ pub enum BlockStatus {
 /// Environment producer for a Consensus instance. Creates proposer instance and communication streams.
 pub trait Environment<B: BlockT> {
 	/// The proposer type this creates.
-	type Proposer: Proposer<B>;
+	type Proposer: Proposer<B> + 'static;
 	/// Error which can occur upon creation.
-	type Error: From<Error>;
+	type Error: From<Error> + std::fmt::Debug + 'static;
 
 	/// Initialize the proposal logic on top of a specific header. Provide
 	/// the authorities at that header.
-	fn init(&mut self, parent_header: &B::Header)
-		-> Result<Self::Proposer, Self::Error>;
+	fn init(&mut self, parent_header: &B::Header) -> Result<Self::Proposer, Self::Error>;
+}
+
+/// A proposal that is created by a [`Proposer`].
+pub struct Proposal<Block: BlockT, Transaction> {
+	/// The block that was build.
+	pub block: Block,
+	/// Optional proof that was recorded while building the block.
+	pub proof: Option<sp_state_machine::StorageProof>,
+	/// The storage changes while building this block.
+	pub storage_changes: sp_state_machine::StorageChanges<Transaction, HasherFor<Block>, NumberFor<Block>>,
+}
+
+/// Used as parameter to [`Proposer`] to tell the requirement on recording a proof.
+///
+/// When `RecordProof::Yes` is given, all accessed trie nodes should be saved. These recorded
+/// trie nodes can be used by a third party to proof this proposal without having access to the
+/// full storage.
+#[derive(Copy, Clone, PartialEq)]
+pub enum RecordProof {
+	/// `Yes`, record a proof.
+	Yes,
+	/// `No`, don't record any proof.
+	No,
+}
+
+impl RecordProof {
+	/// Returns if `Self` == `Yes`.
+	pub fn yes(&self) -> bool {
+		match self {
+			Self::Yes => true,
+			Self::No => false,
+		}
+	}
+}
+
+impl From<bool> for RecordProof {
+	fn from(val: bool) -> Self {
+		if val {
+			Self::Yes
+		} else {
+			Self::No
+		}
+	}
 }
 
 /// Logic for a proposer.
@@ -89,16 +134,29 @@ pub trait Environment<B: BlockT> {
 /// Proposers are generic over bits of "consensus data" which are engine-specific.
 pub trait Proposer<B: BlockT> {
 	/// Error type which can occur when proposing or evaluating.
-	type Error: From<Error> + ::std::fmt::Debug + 'static;
-	/// Future that resolves to a committed proposal.
-	type Create: Future<Output = Result<B, Self::Error>>;
+	type Error: From<Error> + std::fmt::Debug + 'static;
+	/// The transaction type used by the backend.
+	type Transaction: Default + Send + 'static;
+	/// Future that resolves to a committed proposal with an optional proof.
+	type Proposal: Future<Output = Result<Proposal<B, Self::Transaction>, Self::Error>> +
+		Send + Unpin + 'static;
+
 	/// Create a proposal.
+	///
+	/// Gets the `inherent_data` and `inherent_digests` as input for the proposal. Additionally
+	/// a maximum duration for building this proposal is given. If building the proposal takes
+	/// longer than this maximum, the proposal will be very likely discarded.
+	///
+	/// # Return
+	///
+	/// Returns a future that resolves to a [`Proposal`] or to [`Self::Error`].
 	fn propose(
 		&mut self,
 		inherent_data: InherentData,
 		inherent_digests: DigestFor<B>,
 		max_duration: Duration,
-	) -> Self::Create;
+		record_proof: RecordProof,
+	) -> Self::Proposal;
 }
 
 /// An oracle for when major synchronization work is being undertaken.