Child storage tests and genesis fix. (#3185)

* Using child storage, (srml-support only), test failing .

* fix simple tests.

* Enumerable by requiring owned struct (previous form only allow
&'static).
Broken tests are from genesis init.

* implement for_child_keys_with_prefix

* indent

* clear_child_prefix fix.

* clear_child_prefix fix 2.

* fix for storage_impl, if/when allowing child and not child this could be
reverted.

* Fix lot of urlinked child genesis, still need to look upon actual
genesis srml module code.
Probably still a lot of broken code needing debugging.

* switch well_known_key to their associated module child trie.
Fix a genesis init (balance).
Complete some testing.
Comment some tests before using.

* fixing test runtime child keys

* latest commit fix broken genesis init

* fix system balances child name.

* Important fix: storage_root from test externalities need children (it is
already the case for ext).

* executive root with child calculation

* Avoid empty trie on test ext.

* Symetric removal of key for system.

* commenting changes related tests.

* Remove child module specifics.

* fix issues.

* fix some formatting

* fix bench and bump runtime

* Remove extend_storage_overlays, assimilate_storage do the same as is
proper considering srml macro.

* Fix warning for assimilate.

* Removing kill as they do not impact any test cases.

* Use tuple of storage map instead of two parameters. This changes the
behavior of decl_storage genesis build closure (breaking api).

* Do not use build storage before assimilate.

* fix error

* Update core/state-machine/src/backend.rs

substrate/core/state-machine/src/backend.rs

@@ -70,10 +70,14 @@ pub trait Backend<H: Hasher> {
 	/// Retrieve all entries keys of child storage and call `f` for each of those keys.
 	fn for_keys_in_child_storage<F: FnMut(&[u8])>(&self, storage_key: &[u8], f: F);
 
-	/// Retrieve all entries keys of which start with the given prefix and
+	/// Retrieve all entries keys which start with the given prefix and
 	/// call `f` for each of those keys.
 	fn for_keys_with_prefix<F: FnMut(&[u8])>(&self, prefix: &[u8], f: F);
 
+	/// Retrieve all child entries keys which start with the given prefix and
+	/// call `f` for each of those keys.
+	fn for_child_keys_with_prefix<F: FnMut(&[u8])>(&self, storage_key: &[u8], prefix: &[u8], f: F);
+
 	/// Calculate the storage root, with given delta over what is already stored in
 	/// the backend, and produce a "transaction" that can be used to commit.
 	/// Does not include child storage updates.
@@ -103,11 +107,7 @@ pub trait Backend<H: Hasher> {
 	/// Get all keys of child storage with given prefix
 	fn child_keys(&self, child_storage_key: &[u8], prefix: &[u8]) -> Vec<Vec<u8>> {
 		let mut all = Vec::new();
-		self.for_keys_in_child_storage(child_storage_key, |k| {
-			if k.starts_with(prefix) {
-				all.push(k.to_vec());
-			}
-		});
+		self.for_child_keys_with_prefix(child_storage_key, prefix, |k| all.push(k.to_vec()));
 		all
 	}
 
@@ -248,6 +248,25 @@ impl<H: Hasher> From<HashMap<Option<Vec<u8>>, HashMap<Vec<u8>, Vec<u8>>>> for In
 	}
 }
 
+impl<H: Hasher> From<(
+		HashMap<Vec<u8>, Vec<u8>>,
+		HashMap<Vec<u8>, HashMap<Vec<u8>, Vec<u8>>>,
+)> for InMemory<H> {
+	fn from(inners: (
+		HashMap<Vec<u8>, Vec<u8>>,
+		HashMap<Vec<u8>, HashMap<Vec<u8>, Vec<u8>>>,
+	)) -> Self {
+		let mut inner: HashMap<Option<Vec<u8>>, HashMap<Vec<u8>, Vec<u8>>>
+			= inners.1.into_iter().map(|(k, v)| (Some(k), v)).collect();
+		inner.insert(None, inners.0);
+		InMemory {
+			inner: inner,
+			trie: None,
+			_hasher: PhantomData,
+		}
+	}
+}
+
 impl<H: Hasher> From<HashMap<Vec<u8>, Vec<u8>>> for InMemory<H> {
 	fn from(inner: HashMap<Vec<u8>, Vec<u8>>) -> Self {
 		let mut expanded = HashMap::new();
@@ -306,6 +325,11 @@ impl<H: Hasher> Backend<H> for InMemory<H> {
 		self.inner.get(&Some(storage_key.to_vec())).map(|map| map.keys().for_each(|k| f(&k)));
 	}
 
+	fn for_child_keys_with_prefix<F: FnMut(&[u8])>(&self, storage_key: &[u8], prefix: &[u8], f: F) {
+		self.inner.get(&Some(storage_key.to_vec()))
+			.map(|map| map.keys().filter(|key| key.starts_with(prefix)).map(|k| &**k).for_each(f));
+	}
+
 	fn storage_root<I>(&self, delta: I) -> (H::Out, Self::Transaction)
 	where
 		I: IntoIterator<Item=(Vec<u8>, Option<Vec<u8>>)>,