Make working with nested queries a touch easier

examples/examples/dynamic_multisig.rs

@@ -0,0 +1,79 @@
+// Copyright 2019-2022 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+//! To run this example, a local polkadot node should be running. Example verified against polkadot v0.9.31-3711c6f9b2a.
+//!
+//! E.g.
+//! ```bash
+//! curl "https://github.com/paritytech/polkadot/releases/download/v0.9.31/polkadot" --output /usr/local/bin/polkadot --location
+//! polkadot --dev --tmp
+//! ```
+
+use sp_keyring::AccountKeyring;
+use subxt::{
+    dynamic::Value,
+    tx::PairSigner,
+    OnlineClient,
+    PolkadotConfig,
+};
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    tracing_subscriber::fmt::init();
+
+    // My account.
+    let signer_account = AccountKeyring::Alice;
+    let signer_account_id = signer_account.to_account_id();
+    let signer = PairSigner::new(signer_account.pair());
+
+    // Transfer balance to this destination:
+    let dest = AccountKeyring::Bob.to_account_id();
+
+    // Create a client to use:
+    let api = OnlineClient::<PolkadotConfig>::new().await?;
+
+    // Create the inner balance transfer call.
+    let inner_tx = subxt::dynamic::tx(
+        "Balances",
+        "transfer",
+        vec![
+            Value::unnamed_variant("Id", [Value::from_bytes(&dest)]),
+            Value::u128(123_456_789_012_345),
+        ],
+    );
+
+    // Now, build an outer call which this inner call will be a part of.
+    // This sets up the multisig arrangement.
+    //
+    // Note: Since this is a dynamic call, we can either use named or unnamed
+    // arguments (if unnamed, the order matters).
+    let tx = subxt::dynamic::tx(
+        "Multisig",
+        "as_multi",
+        vec![
+            ("threshold", Value::u128(1)),
+            (
+                "other_signatories",
+                Value::unnamed_composite([Value::from_bytes(&signer_account_id)]),
+            ),
+            ("maybe_timepoint", Value::unnamed_variant("None", [])),
+            ("call", inner_tx.into_value()),
+            (
+                "max_weight",
+                Value::named_composite([
+                    ("ref_time", Value::u128(10000000000)),
+                    ("proof_size", Value::u128(1)),
+                ]),
+            ),
+        ],
+    );
+
+    // Submit it:
+    let encoded = hex::encode(&api.tx().call_data(&tx)?);
+    println!("Call data: {encoded}");
+    let tx_hash = api.tx().sign_and_submit_default(&tx, &signer).await?;
+    println!("Submitted tx with hash {tx_hash}");
+
+    Ok(())
+}

examples/examples/multisig.rs

@@ -0,0 +1,76 @@
+// Copyright 2019-2022 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+//! To run this example, a local polkadot node should be running. Example verified against polkadot v0.9.31-3711c6f9b2a.
+//!
+//! E.g.
+//! ```bash
+//! curl "https://github.com/paritytech/polkadot/releases/download/v0.9.31/polkadot" --output /usr/local/bin/polkadot --location
+//! polkadot --dev --tmp
+//! ```
+
+use sp_keyring::AccountKeyring;
+use subxt::{
+    tx::PairSigner,
+    OnlineClient,
+    PolkadotConfig,
+};
+
+#[subxt::subxt(runtime_metadata_path = "../artifacts/polkadot_metadata.scale")]
+pub mod polkadot {}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    tracing_subscriber::fmt::init();
+
+    // My account.
+    let signer_account = AccountKeyring::Alice;
+    let signer_account_id = signer_account.to_account_id();
+    let signer = PairSigner::new(signer_account.pair());
+
+    // Transfer balance to this destination:
+    let dest = AccountKeyring::Bob.to_account_id();
+
+    // Create a client to use:
+    let api = OnlineClient::<PolkadotConfig>::new().await?;
+
+    // Create the inner balance transfer call.
+    //
+    // Note: This call, being manually constructed, will have a specific pallet and call index
+    // which is determined by the generated code. If you're trying to submit this to a node which
+    // has the pallets/calls at different indexes, it will fail. See `dynamic_multisig.rs` for a
+    // workaround in this case which will work regardless of pallet and call indexes.
+    let inner_tx = polkadot::runtime_types::polkadot_runtime::RuntimeCall::Balances(
+        polkadot::runtime_types::pallet_balances::pallet::Call::transfer {
+            dest: dest.into(),
+            value: 123_456_789_012_345,
+        },
+    );
+
+    // Now, build an outer call which this inner call will be a part of.
+    // This sets up the multisig arrangement.
+    let tx = polkadot::tx().multisig().as_multi(
+        // threshold
+        1,
+        // other signatories
+        vec![signer_account_id],
+        // maybe timepoint
+        None,
+        // call
+        inner_tx,
+        // max weight
+        polkadot::runtime_types::sp_weights::weight_v2::Weight {
+            ref_time: 10000000000,
+            proof_size: 1,
+        },
+    );
+
+    // Submit the extrinsic with default params:
+    let encoded = hex::encode(&api.tx().call_data(&tx)?);
+    println!("Call data: {encoded}");
+    let tx_hash = api.tx().sign_and_submit_default(&tx, &signer).await?;
+    println!("Submitted tx with hash {tx_hash}");
+
+    Ok(())
+}

subxt/src/tx/tx_client.rs

@@ -79,7 +79,7 @@ impl<T: Config, C: OfflineClientT<T>> TxClient<T, C> {
     {
         let metadata = self.client.metadata();
         let mut bytes = Vec::new();
-        call.encode_call_data(&metadata, &mut bytes)?;
+        call.encode_call_data_to(&metadata, &mut bytes)?;
         Ok(bytes)
     }
 
@@ -101,7 +101,7 @@ impl<T: Config, C: OfflineClientT<T>> TxClient<T, C> {
             // transaction protocol version (4) (is not signed, so no 1 bit at the front).
             4u8.encode_to(&mut encoded_inner);
             // encode call data after this byte.
-            call.encode_call_data(&self.client.metadata(), &mut encoded_inner)?;
+            call.encode_call_data_to(&self.client.metadata(), &mut encoded_inner)?;
             // now, prefix byte length:
             let len = Compact(
                 u32::try_from(encoded_inner.len())

subxt/src/tx/tx_payload.rs

@@ -14,18 +14,31 @@ use crate::{
     metadata::Metadata,
 };
 use codec::Encode;
+use scale_value::{
+    Composite,
+    ValueDef,
+    Variant,
+};
 use std::borrow::Cow;
 
 /// This represents a transaction payload that can be submitted
 /// to a node.
 pub trait TxPayload {
     /// Encode call data to the provided output.
-    fn encode_call_data(
+    fn encode_call_data_to(
         &self,
         metadata: &Metadata,
         out: &mut Vec<u8>,
     ) -> Result<(), Error>;
 
+    /// Encode call data and return the output. This is a convenience
+    /// wrapper around [`TxPayload::encode_call_data_to`].
+    fn encode_call_data(&self, metadata: &Metadata) -> Result<Vec<u8>, Error> {
+        let mut v = Vec::new();
+        self.encode_call_data_to(metadata, &mut v)?;
+        Ok(v)
+    }
+
     /// Returns the details needed to validate the call, which
     /// include a statically generated hash, the pallet name,
     /// and the call name.
@@ -83,7 +96,7 @@ impl<CallData> StaticTxPayload<CallData> {
 }
 
 impl<CallData: Encode> TxPayload for StaticTxPayload<CallData> {
-    fn encode_call_data(
+    fn encode_call_data_to(
         &self,
         metadata: &Metadata,
         out: &mut Vec<u8>,
@@ -113,32 +126,63 @@ impl<CallData: Encode> TxPayload for StaticTxPayload<CallData> {
 pub struct DynamicTxPayload<'a> {
     pallet_name: Cow<'a, str>,
     call_name: Cow<'a, str>,
-    fields: Vec<Value<()>>,
+    fields: Composite<()>,
+}
+
+impl<'a> DynamicTxPayload<'a> {
+    /// Return the pallet name.
+    pub fn pallet_name(&self) -> &str {
+        &self.pallet_name
+    }
+
+    /// Return the call name.
+    pub fn call_name(&self) -> &str {
+        &self.call_name
+    }
+
+    /// Convert the dynamic payload into a [`Value`]. This is useful
+    /// if you need to submit this as part of a larger call.
+    pub fn into_value(self) -> Value<()> {
+        let call = Value {
+            context: (),
+            value: ValueDef::Variant(Variant {
+                name: self.call_name.into_owned(),
+                values: self.fields,
+            }),
+        };
+
+        Value::unnamed_variant(self.pallet_name, [call])
+    }
 }
 
 /// Construct a new dynamic transaction payload to submit to a node.
 pub fn dynamic<'a>(
     pallet_name: impl Into<Cow<'a, str>>,
     call_name: impl Into<Cow<'a, str>>,
-    fields: Vec<Value<()>>,
+    fields: impl Into<Composite<()>>,
 ) -> DynamicTxPayload<'a> {
     DynamicTxPayload {
         pallet_name: pallet_name.into(),
         call_name: call_name.into(),
-        fields,
+        fields: fields.into(),
     }
 }
 
 impl<'a> TxPayload for DynamicTxPayload<'a> {
-    fn encode_call_data(
+    fn encode_call_data_to(
         &self,
         metadata: &Metadata,
         out: &mut Vec<u8>,
     ) -> Result<(), Error> {
         let pallet = metadata.pallet(&self.pallet_name)?;
         let call_id = pallet.call_ty_id().ok_or(MetadataError::CallNotFound)?;
-        let call_value =
-            Value::unnamed_variant(self.call_name.clone(), self.fields.clone());
+        let call_value = Value {
+            context: (),
+            value: ValueDef::Variant(Variant {
+                name: self.call_name.to_string(),
+                values: self.fields.clone(),
+            }),
+        };
 
         pallet.index().encode_to(out);
         scale_value::scale::encode_as_type(&call_value, call_id, metadata.types(), out)?;