examples: Tx basic with light client for local nodes

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

examples/examples/storage_iterating.rs

@@ -12,7 +12,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let storage_query = polkadot::storage().system().account_root();
 
     // Get back an iterator of results (here, we are fetching 10 items at
-    // a time from the node, but we always iterate over oen at a time).
+    // a time from the node, but we always iterate over one at a time).
     let mut results = api
         .storage()
         .at_latest()

examples/examples/unstable_light_client_tx_basic.rs

@@ -0,0 +1,70 @@
+use sp_keyring::AccountKeyring;
+use std::sync::Arc;
+use subxt::{rpc::LightClient, tx::PairSigner, OnlineClient, PolkadotConfig};
+
+// Generate an interface that we can use from the node's metadata.
+#[subxt::subxt(runtime_metadata_path = "../artifacts/polkadot_metadata_small.scale")]
+pub mod polkadot {}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Create a light client from the provided chain spec.
+    //
+    // # Note
+    //
+    // This example uses a local running polkadot node and the
+    // provided spec might differ depending on the version used.
+    //
+    // The spec can be generated in the following manner:
+    // - start the polkadot node:
+    //
+    // `./polkadot --dev --node-key 0000000000000000000000000000000000000000000000000000000000000001  --alice --validator`
+    //
+    // - fetch the spec
+    //
+    // ```bash
+    // curl -H "Content-Type: application/json" -d '{"id":1, "jsonrpc":"2.0", "method": "sync_state_genSyncSpec", "params":[true]}' http://localhost:9944/ | jq .result > res.spec
+    // ```
+    //
+    // - remove the `lightSyncState` entry from the spec
+    //
+    // - add the boot nodes entry to the spec
+    //
+    // ```json
+    //   "bootNodes": [
+    //       "/ip4/127.0.0.1/tcp/30333/p2p/12D3KooWEyoppNCUx8Yx66oV9fJnriXwCcXwDDUA2kj6vnc6iDEp"
+    //    ],
+    //
+    // Where `12D3KooWEyoppNCUx8Yx66oV9fJnriXwCcXwDDUA2kj6vnc6iDEp` should be replaced with the
+    // polkadot nodes identity extracted from the process's logs:
+    //
+    // ```bash
+    // 👴 Loading GRANDPA authority set from genesis on what appears to be first startup.
+    // 👶 Creating empty BABE epoch changes on what appears to be first startup.
+    // 🏷 Local node identity is: 12D3KooWEyoppNCUx8Yx66oV9fJnriXwCcXwDDUA2kj6vnc6iDEp
+    // ```
+    let light_client = LightClient::new(include_str!("../../artifacts/dev_spec.json"))?;
+    let api = OnlineClient::<PolkadotConfig>::from_rpc_client(Arc::new(light_client)).await?;
+
+    // Build a balance transfer extrinsic.
+    let dest = AccountKeyring::Bob.to_account_id().into();
+    let balance_transfer_tx = polkadot::tx().balances().transfer(dest, 10_000);
+
+    // Submit the balance transfer extrinsic from Alice, and wait for it to be successful
+    // and in a finalized block. We get back the extrinsic events if all is well.
+    let from = PairSigner::new(AccountKeyring::Alice.pair());
+    let events = api
+        .tx()
+        .sign_and_submit_then_watch_default(&balance_transfer_tx, &from)
+        .await?
+        .wait_for_finalized_success()
+        .await?;
+
+    // Find a Transfer event and print it.
+    let transfer_event = events.find_first::<polkadot::balances::events::Transfer>()?;
+    if let Some(event) = transfer_event {
+        println!("Balance transfer success: {event:?}");
+    }
+
+    Ok(())
+}