feat(governance): 🧊 test that community pool spend proposals can be d…

…isabled (#4222)

fixes #4079. related to, but does not finish #2105.

this introduces test coverage to show that community pool spend
proposals can be disabled via a chain parameter.

### related changes

some changes made, related to writing tests for the governance
component:

* 6b3be58 refactor(governance): 💶 `Value` accessors for proposal
actions
* de16dac feat(tx): 🌮 `ActionPlan: From` for community pool actions
* 4e6b874 feat(amount): ➖ `Amount: std::ops::SubAssign`

### tests

this addresses part of #2105. we should add tests that exercise the
other
tallying logic before that issue is complete. tests are added in the
following
commits:

* fedfa8d tests(app): 💭 test a community pool spend
* 201fe48 tests(app): 🏊 test a community pool deposit
* 8543869 tests(app): 🥶 test that community pool can be frozen

crates/core/app/tests/app_can_deposit_into_community_pool.rs

@@ -0,0 +1,129 @@
+use {
+    self::common::BuilderExt,
+    anyhow::anyhow,
+    cnidarium::TempStorage,
+    penumbra_app::{genesis::AppState, server::consensus::Consensus},
+    penumbra_asset::asset,
+    penumbra_community_pool::{CommunityPoolDeposit, StateReadExt},
+    penumbra_keys::test_keys,
+    penumbra_mock_client::MockClient,
+    penumbra_mock_consensus::TestNode,
+    penumbra_num::Amount,
+    penumbra_proto::DomainType,
+    penumbra_shielded_pool::SpendPlan,
+    penumbra_transaction::{TransactionParameters, TransactionPlan},
+    rand_core::OsRng,
+    std::collections::BTreeMap,
+    tap::{Tap, TapFallible},
+    tracing::info,
+};
+
+mod common;
+
+/// Exercises that the app can deposit a note into the community pool.
+#[tokio::test]
+async fn app_can_deposit_into_community_pool() -> anyhow::Result<()> {
+    // Install a test logger, and acquire some temporary storage.
+    let guard = common::set_tracing_subscriber();
+    let storage = TempStorage::new().await?;
+
+    // Define our application state, and start the test node.
+    let mut test_node = {
+        let app_state = AppState::default();
+        let consensus = Consensus::new(storage.as_ref().clone());
+        TestNode::builder()
+            .single_validator()
+            .with_penumbra_auto_app_state(app_state)?
+            .init_chain(consensus)
+            .await
+            .tap_ok(|e| tracing::info!(hash = %e.last_app_hash_hex(), "finished init chain"))?
+    };
+
+    // Sync the mock client, using the test wallet's spend key, to the latest snapshot.
+    let client = MockClient::new(test_keys::SPEND_KEY.clone())
+        .with_sync_to_storage(&storage)
+        .await?
+        .tap(|c| info!(client.notes = %c.notes.len(), "mock client synced to test storage"));
+
+    // Take one of the test wallet's notes, and prepare to deposit it in the community pool.
+    let note = client
+        .notes
+        .values()
+        .cloned()
+        .next()
+        .ok_or_else(|| anyhow!("mock client had no note"))?;
+
+    // Create a community pool transaction.
+    let mut plan = {
+        let value = note.value();
+        let spend = SpendPlan::new(
+            &mut OsRng,
+            note.clone(),
+            client
+                .position(note.commit())
+                .ok_or_else(|| anyhow!("input note commitment was unknown to mock client"))?,
+        )
+        .into();
+        let deposit = CommunityPoolDeposit { value }.into();
+        TransactionPlan {
+            actions: vec![spend, deposit],
+            // Now fill out the remaining parts of the transaction needed for verification:
+            memo: None,
+            detection_data: None, // We'll set this automatically below
+            transaction_parameters: TransactionParameters {
+                chain_id: TestNode::<()>::CHAIN_ID.to_string(),
+                ..Default::default()
+            },
+        }
+    };
+    plan.populate_detection_data(OsRng, 0);
+    let tx = client.witness_auth_build(&plan).await?;
+
+    // Execute the transaction, applying it to the chain state.
+    let pre_tx_snapshot = storage.latest_snapshot();
+    test_node
+        .block()
+        .with_data(vec![tx.encode_to_vec()])
+        .execute()
+        .await?;
+    let post_tx_snapshot = storage.latest_snapshot();
+
+    // Assert that the community pool balance looks correct for the deposited asset id, and that
+    // other amounts were not affected by the deposit.
+    {
+        type Balance = BTreeMap<asset::Id, Amount>;
+
+        let id = note.asset_id();
+        let pre_tx_balance = pre_tx_snapshot.community_pool_balance().await?;
+        let post_tx_balance = post_tx_snapshot.community_pool_balance().await?;
+
+        let get_balance_for_id = |balance: &Balance| balance.get(&id).copied().unwrap_or_default();
+        let pre_tx_amount = get_balance_for_id(&pre_tx_balance);
+        let post_tx_amount = get_balance_for_id(&post_tx_balance);
+        assert_eq!(
+            pre_tx_amount + note.amount(),
+            post_tx_amount,
+            "community pool balance should include the deposited note"
+        );
+
+        let count_other_assets_in_pool = |balance: &Balance| {
+            balance
+                .into_iter()
+                // Skip the amount for our note's asset id.
+                .filter(|(&entry_id, _)| entry_id != id)
+                .map(|(_, &amount)| amount)
+                .sum::<Amount>()
+        };
+        assert_eq!(
+            count_other_assets_in_pool(&pre_tx_balance),
+            count_other_assets_in_pool(&post_tx_balance),
+            "other community pool balance amounts should not have changed"
+        );
+    }
+
+    // Free our temporary storage.
+    Ok(())
+        .tap(|_| drop(test_node))
+        .tap(|_| drop(storage))
+        .tap(|_| drop(guard))
+}