sc-block-builder: Remove BlockBuilderProvider (#2099)

The `BlockBuilderProvider` was a trait that was defined in
`sc-block-builder`. The trait was implemented for `Client`. This
basically meant that you needed to import `sc-block-builder` any way to
have access to the block builder. So, this trait was not providing any
real value. This pull request is removing the said trait. Instead of the
trait it introduces a builder for creating a `BlockBuilder`. The builder
currently has the quite fabulous name `BlockBuilderBuilder` (I'm open to
any better name 😅). The rest of the pull request is about
replacing the old trait with the new builder.

# Downstream code changes

If you used `new_block` or `new_block_at` before you now need to switch
it over to the new `BlockBuilderBuilder` pattern:

```rust
// `new` requires a type that implements `CallApiAt`. 
let mut block_builder = BlockBuilderBuilder::new(client)
                // Then you need to specify the hash of the parent block the block will be build on top of
		.on_parent_block(at)
                // The block builder also needs the block number of the parent block. 
                // Here it is fetched from the given `client` using the `HeaderBackend`
                // However, there also exists `with_parent_block_number` for directly passing the number
		.fetch_parent_block_number(client)
		.unwrap()
                // Enable proof recording if required. This call is optional.
		.enable_proof_recording()
                // Pass the digests. This call is optional.
                .with_inherent_digests(digests)
		.build()
		.expect("Creates new block builder");
```

---------

Co-authored-by: Sebastian Kunert <skunert49@gmail.com>
Co-authored-by: command-bot <>

polkadot/node/test/client/src/block_builder.rs

@@ -14,12 +14,12 @@
 // You should have received a copy of the GNU General Public License
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
-use crate::{Client, FullBackend};
+use crate::Client;
 use parity_scale_codec::{Decode, Encode};
 use polkadot_primitives::{Block, InherentData as ParachainsInherentData};
 use polkadot_test_runtime::UncheckedExtrinsic;
 use polkadot_test_service::GetLastTimestamp;
-use sc_block_builder::{BlockBuilder, BlockBuilderProvider};
+use sc_block_builder::{BlockBuilder, BlockBuilderBuilder};
 use sp_api::ProvideRuntimeApi;
 use sp_consensus_babe::{
 	digests::{PreDigest, SecondaryPlainPreDigest},
@@ -34,9 +34,7 @@ pub trait InitPolkadotBlockBuilder {
 	///
 	/// This will automatically create and push the inherents for you to make the block valid for
 	/// the test runtime.
-	fn init_polkadot_block_builder(
-		&self,
-	) -> sc_block_builder::BlockBuilder<Block, Client, FullBackend>;
+	fn init_polkadot_block_builder(&self) -> sc_block_builder::BlockBuilder<Block, Client>;
 
 	/// Init a Polkadot specific block builder at a specific block that works for the test runtime.
 	///
@@ -45,11 +43,11 @@ pub trait InitPolkadotBlockBuilder {
 	fn init_polkadot_block_builder_at(
 		&self,
 		hash: <Block as BlockT>::Hash,
-	) -> sc_block_builder::BlockBuilder<Block, Client, FullBackend>;
+	) -> sc_block_builder::BlockBuilder<Block, Client>;
 }
 
 impl InitPolkadotBlockBuilder for Client {
-	fn init_polkadot_block_builder(&self) -> BlockBuilder<Block, Client, FullBackend> {
+	fn init_polkadot_block_builder(&self) -> BlockBuilder<Block, Client> {
 		let chain_info = self.chain_info();
 		self.init_polkadot_block_builder_at(chain_info.best_hash)
 	}
@@ -57,7 +55,7 @@ impl InitPolkadotBlockBuilder for Client {
 	fn init_polkadot_block_builder_at(
 		&self,
 		hash: <Block as BlockT>::Hash,
-	) -> BlockBuilder<Block, Client, FullBackend> {
+	) -> BlockBuilder<Block, Client> {
 		let last_timestamp =
 			self.runtime_api().get_last_timestamp(hash).expect("Get last timestamp");
 
@@ -90,8 +88,12 @@ impl InitPolkadotBlockBuilder for Client {
 			)],
 		};
 
-		let mut block_builder = self
-			.new_block_at(hash, digest, false)
+		let mut block_builder = BlockBuilderBuilder::new(self)
+			.on_parent_block(hash)
+			.fetch_parent_block_number(&self)
+			.expect("Fetches parent block number")
+			.with_inherent_digests(digest)
+			.build()
 			.expect("Creates new block builder for test runtime");
 
 		let mut inherent_data = sp_inherents::InherentData::new();
@@ -144,7 +146,7 @@ pub trait BlockBuilderExt {
 	) -> Result<(), sp_blockchain::Error>;
 }
 
-impl BlockBuilderExt for BlockBuilder<'_, Block, Client, FullBackend> {
+impl BlockBuilderExt for BlockBuilder<'_, Block, Client> {
 	fn push_polkadot_extrinsic(
 		&mut self,
 		ext: UncheckedExtrinsic,