Introduce on_open_block

`on_open_block` is called when the block is created, before
processing any transactions included in the block.

Author: remagpie

core/src/block.rs

@@ -313,6 +313,10 @@ impl<'x> OpenBlock<'x> {
         self.block.header.set_seal(seal);
         Ok(())
     }
+
+    pub fn inner_mut(&mut self) -> &mut ExecutedBlock {
+        &mut self.block
+    }
 }
 
 /// Just like `OpenBlock`, except that we've applied `Engine::on_close_block`, finished up the non-seal header fields.
@@ -492,6 +496,7 @@ pub fn enact<C: ChainTimeInfo + EngineInfo + FindActionHandler + TermInfo>(
     let mut b = OpenBlock::try_new(engine, db, parent, Address::default(), vec![])?;
 
     b.populate_from(header);
+    engine.on_open_block(b.inner_mut())?;
     b.push_transactions(transactions, client, parent.number(), parent.timestamp())?;
 
     let term_common_params = client.term_common_params(BlockId::Hash(*header.parent_hash()));

core/src/consensus/mod.rs

@@ -222,6 +222,11 @@ pub trait ConsensusEngine: Sync + Send {
     /// Stops any services that the may hold the Engine and makes it safe to drop.
     fn stop(&self) {}
 
+    /// Block transformation functions, before the transactions.
+    fn on_open_block(&self, _block: &mut ExecutedBlock) -> Result<(), Error> {
+        Ok(())
+    }
+
     /// Block transformation functions, after the transactions.
     fn on_close_block(
         &self,

core/src/consensus/tendermint/engine.rs

@@ -141,6 +141,15 @@ impl ConsensusEngine for Tendermint {
 
     fn stop(&self) {}
 
+    /// Block transformation functions, before the transactions.
+    fn on_open_block(&self, block: &mut ExecutedBlock) -> Result<(), Error> {
+        let metadata = block.state().metadata()?.expect("Metadata must exist");
+        if block.header().number() == metadata.last_term_finished_block_num() + 1 {
+            // FIXME: on_term_open
+        }
+        Ok(())
+    }
+
     fn on_close_block(
         &self,
         block: &mut ExecutedBlock,

core/src/miner/miner.rs

@@ -527,6 +527,7 @@ impl Miner {
                 return Ok(None)
             }
         }
+        self.engine.on_open_block(open_block.inner_mut())?;
 
         let mut invalid_transactions = Vec::new();