Set balance below existential (#1983)

* Added check to panic when set_account_balance receives a value less than the existential minimum

* Restored comment

* Used ChainSpec::default().minimum_balance as minimum

* Removed the 0 from the check to reap the account

* Removed tabs and spaces

* Added comment for the 0 balance option

* Updated CHANGELOG.md

* Added tests for set_account_balance

* cargo fmt and cargo clippy

CHANGELOG.md

@@ -200,6 +200,7 @@ See [the compatibility section](https://use.ink/faq/migrating-from-ink-4-to-5/#c
 - Split up `ink_linting` to mandatory and extra libraries - [#2032](https://github.com/use-ink/ink/pull/2032)
 - [E2E] resolve DispatchError error details for dry-runs - [#1994](https://github.com/use-ink/ink/pull/1994)
 - [E2E] update to new `drink` API - [#2005](https://github.com/use-ink/ink/pull/2005)
+- [E2E] `set_account_balance` now can't set balance below existential deposit - [#1983](https://github.com/paritytech/ink/pull/1983)
 
 
 ## Version 5.0.0-alpha

crates/env/src/engine/off_chain/test_api.rs

@@ -27,7 +27,10 @@ use ink_engine::test_api::RecordedDebugMessages;
 use std::panic::UnwindSafe;
 
 pub use super::call_data::CallData;
-pub use ink_engine::ChainExtension;
+pub use ink_engine::{
+    ext::ChainSpec,
+    ChainExtension,
+};
 
 /// Record for an emitted event.
 #[derive(Clone)]
@@ -45,15 +48,27 @@ pub struct EmittedEvent {
 /// Note that account could refer to either a user account or
 /// a smart contract account.
 ///
+/// If a 0 balance is set, this would not fail. This is useful for
+/// reaping an account.
+///
 /// # Errors
 ///
 /// - If `account` does not exist.
 /// - If the underlying `account` type does not match.
 /// - If the underlying `new_balance` type does not match.
+/// - If the `new_balance` is less than the existential minimum.
 pub fn set_account_balance<T>(account_id: T::AccountId, new_balance: T::Balance)
 where
     T: Environment<Balance = u128>, // Just temporary for the MVP!
 {
+    let min = ChainSpec::default().minimum_balance;
+    if new_balance < min && new_balance != 0u128 {
+        panic!(
+            "Balance must be at least [{}]. Use 0 as balance to reap the account.",
+            min
+        );
+    }
+
     <EnvInstance as OnInstance>::on_instance(|instance| {
         instance
             .engine

crates/env/src/engine/off_chain/tests.rs

@@ -13,8 +13,13 @@
 // limitations under the License.
 
 use crate::{
-    engine::off_chain::impls::TopicsBuilder,
+    engine::off_chain::{
+        impls::TopicsBuilder,
+        test_api::set_account_balance,
+    },
     event::TopicsBuilderBackend,
+    types::Environment,
+    DefaultEnvironment,
     Result,
 };
 
@@ -41,3 +46,32 @@ fn topics_builder() -> Result<()> {
         Ok(())
     })
 }
+#[test]
+fn test_set_account_balance() -> Result<()> {
+    pub use ink_engine::ext::ChainSpec;
+
+    crate::test::run_test::<DefaultEnvironment, _>(|_| {
+        let minimum_balance = ChainSpec::default().minimum_balance;
+
+        let result = std::panic::catch_unwind(|| {
+            set_account_balance::<DefaultEnvironment>(
+                <DefaultEnvironment as Environment>::AccountId::from([0x1; 32]),
+                <DefaultEnvironment as Environment>::Balance::from(minimum_balance - 1),
+            )
+        });
+
+        assert!(result.is_err());
+
+        set_account_balance::<DefaultEnvironment>(
+            <DefaultEnvironment as Environment>::AccountId::from([0x1; 32]),
+            <DefaultEnvironment as Environment>::Balance::from(0u128),
+        );
+
+        set_account_balance::<DefaultEnvironment>(
+            <DefaultEnvironment as Environment>::AccountId::from([0x1; 32]),
+            <DefaultEnvironment as Environment>::Balance::from(minimum_balance + 1),
+        );
+
+        Ok(())
+    })
+}