Allow PartialExtrinsic to be held across await points (#1658)

* Allow PartialTransaction to be held across await points, and example to prove it

* Add comment to tx_parital example

* Fix book link

core/src/config/extrinsic_params.rs

@@ -14,7 +14,7 @@ use alloc::vec::Vec;
 /// This trait allows you to configure the "signed extra" and
 /// "additional" parameters that are a part of the transaction payload
 /// or the signer payload respectively.
-pub trait ExtrinsicParams<T: Config>: ExtrinsicParamsEncoder + Sized + 'static {
+pub trait ExtrinsicParams<T: Config>: ExtrinsicParamsEncoder + Sized + Send + 'static {
     /// These parameters can be provided to the constructor along with
     /// some default parameters that `subxt` understands, in order to
     /// help construct your [`ExtrinsicParams`] object.

core/src/config/mod.rs

@@ -58,7 +58,7 @@ pub trait Config: Sized + Send + Sync + 'static {
     type ExtrinsicParams: ExtrinsicParams<Self>;
 
     /// This is used to identify an asset in the `ChargeAssetTxPayment` signed extension.
-    type AssetId: Debug + Clone + Encode + DecodeAsType + EncodeAsType;
+    type AssetId: Debug + Clone + Encode + DecodeAsType + EncodeAsType + Send;
 }
 
 /// given some [`Config`], this return the other params needed for its `ExtrinsicParams`.

core/src/config/signed_extensions.rs

@@ -435,7 +435,7 @@ impl<T: Config> SignedExtension<T> for ChargeTransactionPayment {
 /// ones are actually required for the chain in the correct order, ignoring the rest. This
 /// is a sensible default, and allows for a single configuration to work across multiple chains.
 pub struct AnyOf<T, Params> {
-    params: Vec<Box<dyn ExtrinsicParamsEncoder>>,
+    params: Vec<Box<dyn ExtrinsicParamsEncoder + Send + 'static>>,
     _marker: core::marker::PhantomData<(T, Params)>,
 }
 
@@ -470,7 +470,7 @@ macro_rules! impl_tuples {
                         // Break and record as soon as we find a match:
                         if $ident::matches(e.identifier(), e.extra_ty(), types) {
                             let ext = $ident::new(client, params.$index)?;
-                            let boxed_ext: Box<dyn ExtrinsicParamsEncoder> = Box::new(ext);
+                            let boxed_ext: Box<dyn ExtrinsicParamsEncoder + Send + 'static> = Box::new(ext);
                             exts_by_index.insert(idx, boxed_ext);
                             break
                         }