Contracts module rejig (#1358)

* Move prepare under code.

* Schedule update

* CodeHash

* create takes code_hash

* pass mem def and use code in vm::execute

* Actually save and load code

* Use T::Hash as CodeHash

* Explicit entrypoint name

* Return code_hash and deposit an Event

* Charge for deployed code with gas.

* ImportSatisfyCheck and FunctionImplProvider

* Progress.

* Use new infrastructure for checking imports

* Rename entrypoint to entrypoint_name

* Use strings instead of a Error enum

* Clean

* WIP

* Fix macro_define_env test.

* Fix vm code tests.

* Remove tests for now.

* Fix borked merge

* Fix build for wasm

* fmt

* Scaffolding for abstracting vm.

* Hook up execution to exec layer.

* Fix vm tests.

* Use schedule directly in WasmLoader

* Implement test language.

* Add input_data test.

* Max depth test

* ext_caller

* Simplify test.

* Add TODO

* Some tests and todos.

* top_level

* Clean.

* Restore a couple of integration tests.

* Add a few comments.

* Add ext_address runtime call.

* Deduplicate caller/self_account

* Add not_exists test.

* Change bool to TransferCause.

* Add address tests.

* Remove output_buf from parameter.

* return from start fn.

* Smart gas meter

* Tracing

* Fix prepare tests.

* Code moving

* Add ExecFeeToken

* Use tokens everywhere.

* Make it compile in no_std.

* Lift all test requirements to TestAuxiliaries

* A minor clean

* First create tests

* Remove unneeded TODO

* Docs.

* Code shuffling

* Rename create → instantiate

* Add test address.

* Code shuffling

* Add base_fee tests.

* rejig the code

* Add some comments

* on_finalise comment

* Move event deposit further

* Update Cargo.lock

* Use crates.io version of pwasm-utils

* Format todo comments

* Fix formatting

* Comments

* EmptyOutputBuf and OutputBuf split.

* Restore code_hash

* Fix node-executor.

* Fix typo

* Fix fmt

* Update srml/contract/src/account_db.rs

Co-Authored-By: pepyakin <s.pepyakin@gmail.com>

* Update srml/contract/src/lib.rs

Co-Authored-By: pepyakin <s.pepyakin@gmail.com>

* Line wraps

* Wrapping macros

* Add _ prefix

* Grumbles

* Doc updates.

* Update srml/contract/src/wasm/mod.rs

Co-Authored-By: pepyakin <s.pepyakin@gmail.com>

* Update srml/contract/src/lib.rs

Co-Authored-By: pepyakin <s.pepyakin@gmail.com>

* Add comment

* Use saturation to signal overflow

* Add prepare_test! macro

* Require deploy function.

* Add entry point tests

* Add comment.

* Rename code → code_cache to better describe

* Get rid of weird match!

* Recompile binaries

* Add comments

* refuse_instantiate_with_value_below_existential_deposit

* Little fix

* Make test more complete

* Clean

* Add integration test for instantiation

* Rebuild runtime.

* Add some tests.

* Attach an issue to a TODO

* Attach another issue

* Apply suggestions from code review

Co-Authored-By: pepyakin <s.pepyakin@gmail.com>

* Update srml/contract/src/exec.rs

Co-Authored-By: pepyakin <s.pepyakin@gmail.com>

* Update srml/contract/src/exec.rs

Co-Authored-By: pepyakin <s.pepyakin@gmail.com>

* Recompile node_runtime

substrate/srml/contract/src/account_db.rs

@@ -16,7 +16,7 @@
 
 //! Auxilliaries to help with managing partial changes to accounts state.
 
-use super::{CodeOf, StorageOf, Trait};
+use super::{CodeHash, CodeHashOf, StorageOf, Trait};
 use rstd::cell::RefCell;
 use rstd::collections::btree_map::{BTreeMap, Entry};
 use rstd::prelude::*;
@@ -25,7 +25,8 @@ use {balances, system};
 
 pub struct ChangeEntry<T: Trait> {
 	balance: Option<T::Balance>,
-	code: Option<Vec<u8>>,
+	/// In the case the outer option is None, the code_hash remains untouched, while providing `Some(None)` signifies a removing of the code in question
+	code: Option<Option<CodeHash<T>>>,
 	storage: BTreeMap<Vec<u8>, Option<Vec<u8>>>,
 }
 
@@ -44,7 +45,7 @@ pub type ChangeSet<T> = BTreeMap<<T as system::Trait>::AccountId, ChangeEntry<T>
 
 pub trait AccountDb<T: Trait> {
 	fn get_storage(&self, account: &T::AccountId, location: &[u8]) -> Option<Vec<u8>>;
-	fn get_code(&self, account: &T::AccountId) -> Vec<u8>;
+	fn get_code(&self, account: &T::AccountId) -> Option<CodeHash<T>>;
 	fn get_balance(&self, account: &T::AccountId) -> T::Balance;
 
 	fn commit(&mut self, change_set: ChangeSet<T>);
@@ -55,8 +56,8 @@ impl<T: Trait> AccountDb<T> for DirectAccountDb {
 	fn get_storage(&self, account: &T::AccountId, location: &[u8]) -> Option<Vec<u8>> {
 		<StorageOf<T>>::get(account.clone(), location.to_vec())
 	}
-	fn get_code(&self, account: &T::AccountId) -> Vec<u8> {
-		<CodeOf<T>>::get(account)
+	fn get_code(&self, account: &T::AccountId) -> Option<CodeHash<T>> {
+		<CodeHashOf<T>>::get(account)
 	}
 	fn get_balance(&self, account: &T::AccountId) -> T::Balance {
 		balances::Module::<T>::free_balance(account)
@@ -68,13 +69,17 @@ impl<T: Trait> AccountDb<T> for DirectAccountDb {
 					balances::Module::<T>::set_free_balance_creating(&address, balance)
 				{
 					// Account killed. This will ultimately lead to calling `OnFreeBalanceZero` callback
-					// which will make removal of CodeOf and StorageOf for this account.
+					// which will make removal of CodeHashOf and StorageOf for this account.
 					// In order to avoid writing over the deleted properties we `continue` here.
 					continue;
 				}
 			}
 			if let Some(code) = changed.code {
-				<CodeOf<T>>::insert(&address, &code);
+				if let Some(code) = code {
+					<CodeHashOf<T>>::insert(&address, code);
+				} else {
+					<CodeHashOf<T>>::remove(&address);
+				}
 			}
 			for (k, v) in changed.storage.into_iter() {
 				if let Some(value) = v {
@@ -116,7 +121,7 @@ impl<'a, T: Trait> OverlayAccountDb<'a, T> {
 			.storage
 			.insert(location, value);
 	}
-	pub fn set_code(&mut self, account: &T::AccountId, code: Vec<u8>) {
+	pub fn set_code(&mut self, account: &T::AccountId, code: Option<CodeHash<T>>) {
 		self.local
 			.borrow_mut()
 			.entry(account.clone())
@@ -141,7 +146,7 @@ impl<'a, T: Trait> AccountDb<T> for OverlayAccountDb<'a, T> {
 			.cloned()
 			.unwrap_or_else(|| self.underlying.get_storage(account, location))
 	}
-	fn get_code(&self, account: &T::AccountId) -> Vec<u8> {
+	fn get_code(&self, account: &T::AccountId) -> Option<CodeHash<T>> {
 		self.local
 			.borrow()
 			.get(account)