RPC to query transaction fee + weight + info (#3876)

* initial version for testing

* New version that compiles

* optional at block parameter

* Fix some more view grumbles.

* Update srml/transaction-payment/src/lib.rs

substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs

@@ -23,6 +23,7 @@ use codec::{Decode, Encode, EncodeLike, Input, Error};
 use crate::{
 	traits::{self, Member, MaybeDisplay, SignedExtension, Checkable, Extrinsic, IdentifyAccount},
 	generic::CheckedExtrinsic, transaction_validity::{TransactionValidityError, InvalidTransaction},
+	weights::{GetDispatchInfo, DispatchInfo},
 };
 
 const TRANSACTION_VERSION: u8 = 4;
@@ -280,6 +281,17 @@ where
 	}
 }
 
+impl<Address, Call, Signature, Extra> GetDispatchInfo
+	for UncheckedExtrinsic<Address, Call, Signature, Extra>
+where
+	Call: GetDispatchInfo,
+	Extra: SignedExtension,
+{
+	fn get_dispatch_info(&self) -> DispatchInfo {
+		self.function.get_dispatch_info()
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;

substrate/core/sr-primitives/src/weights.rs

@@ -35,9 +35,13 @@
 //! Note that the decl_module macro _cannot_ enforce this and will simply fail if an invalid struct
 //! (something that does not  implement `Weighable`) is passed in.
 
+#[cfg(feature = "std")]
+use serde::{Serialize, Deserialize};
+use codec::{Encode, Decode};
 use arithmetic::traits::Bounded;
 use crate::RuntimeDebug;
 
+/// Re-export priority as type
 pub use crate::transaction_validity::TransactionPriority;
 
 /// Numeric range of a transaction weight.
@@ -58,10 +62,10 @@ pub trait ClassifyDispatch<T> {
 	fn classify_dispatch(&self, target: T) -> DispatchClass;
 }
 
-/// A generalized group of dispatch types. This is only distinguishing normal, user-triggered
-/// transactions (`Normal`) and anything beyond which serves a higher purpose to the system
-/// (`Operational`).
-#[derive(PartialEq, Eq, Clone, Copy, RuntimeDebug)]
+/// A generalized group of dispatch types. This is only distinguishing normal, user-triggered transactions
+/// (`Normal`) and anything beyond which serves a higher purpose to the system (`Operational`).
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize))]
+#[derive(PartialEq, Eq, Clone, Copy, Encode, Decode, RuntimeDebug)]
 pub enum DispatchClass {
 	/// A normal dispatch.
 	Normal,