Include default values in storage metadata (#1264)

* Add a 'default' field to metadata. It contains code to generate the
default value.

* wasm update

* Make 'default' field an `Option`

* Boxed fn is not static, that won't be fine

* static fn won't do it to as it cannot get T param, will try fat trait

* Fat pointer over phantom data compatible with static instantiation

* DecodeDifferent is cool, using it for decoding.

* using once cell to do what would require copying lazy_static internals.

* Remove cache when no_std (non compatible deps)

* wasm bins update

* Fuse tooling struct and enum derive.

substrate/srml/support/src/metadata.rs

@@ -15,7 +15,8 @@
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
 
 pub use srml_metadata::{
-	DecodeDifferent, FnEncode, RuntimeMetadata, RuntimeModuleMetadata
+	DecodeDifferent, FnEncode, RuntimeMetadata, RuntimeModuleMetadata,
+	DefaultByteGetter,
 };
 
 /// Implements the metadata support for the given runtime and all its modules.
@@ -188,7 +189,7 @@ mod tests {
 				StorageMethod : Option<u32>;
 			}
 			add_extra_genesis {
-			    build(|_, _, _| {});
+				build(|_, _, _| {});
 			}
 		}
 	}
@@ -311,15 +312,20 @@ mod tests {
 				)),
 				storage: Some(DecodeDifferent::Encode(FnEncode(||
 					StorageMetadata {
-					   prefix: DecodeDifferent::Encode("TestStorage"),
-					   functions: DecodeDifferent::Encode(&[
-						   StorageFunctionMetadata {
-							   name: DecodeDifferent::Encode("StorageMethod"),
-							   modifier: StorageFunctionModifier::Optional,
-							   ty: StorageFunctionType::Plain(DecodeDifferent::Encode("u32")),
-							   documentation: DecodeDifferent::Encode(&[]),
-						   }
-					   ])
+						prefix: DecodeDifferent::Encode("TestStorage"),
+						functions: DecodeDifferent::Encode(&[
+							StorageFunctionMetadata {
+								name: DecodeDifferent::Encode("StorageMethod"),
+								modifier: StorageFunctionModifier::Optional,
+								ty: StorageFunctionType::Plain(DecodeDifferent::Encode("u32")),
+								default: DecodeDifferent::Encode(
+									DefaultByteGetter(
+										&event_module2::__GetByteStructStorageMethod(::std::marker::PhantomData::<TestRuntime>)
+									)
+								),
+								documentation: DecodeDifferent::Encode(&[]),
+							}
+						])
 					}
 				))),
 			}