fix: refund on error

Author: gagdiez

src/deploy.rs

@@ -1,5 +1,5 @@
 use near_contract_standards::fungible_token::metadata::FungibleTokenMetadata;
-use near_sdk::{borsh, env, json_types::U128, near, require, AccountId, NearToken, Promise};
+use near_sdk::{borsh, env, json_types::U128, log, near, require, serde_json::json, AccountId, NearToken, Promise, PromiseError};
 
 use crate::{Contract, ContractExt, FT_CONTRACT, NO_DEPOSIT, TGAS};
 
@@ -59,6 +59,12 @@ impl Contract {
 
         let init_args = near_sdk::serde_json::to_vec(&args).unwrap();
 
+        let user = env::predecessor_account_id();
+        let callback_args = json!({ "user": user, "deposit": attached })
+            .to_string()
+            .into_bytes()
+            .to_vec();
+
         Promise::new(token_account_id.parse().unwrap())
             .create_account()
             .transfer(attached)
@@ -69,5 +75,28 @@ impl Contract {
                 NO_DEPOSIT,
                 TGAS.saturating_mul(50),
             )
+            .then(Promise::new(env::current_account_id()).function_call(
+                "create_callback".to_string(),
+                callback_args,
+                NearToken::from_near(0),
+                TGAS.saturating_mul(30),
+            ))
+    }
+
+    #[private]
+    pub fn create_callback(
+        &self,
+        user: AccountId,
+        deposit: NearToken,
+        #[callback_result] call_result: Result<(), PromiseError>,
+    ) -> bool {
+        match call_result {
+            Ok(_) => true,
+            Err(e) => {
+                log!("Error creating token: {:?}", e);
+                Promise::new(user).transfer(deposit);
+                false
+            }
+        }
     }
 }

tests/sandbox.rs

@@ -30,7 +30,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .transact()
         .await?
         .into_result()?;
-    
+
     let bob_account = root
         .create_subaccount("bob")
         .initial_balance(NearToken::from_near(5))
@@ -50,7 +50,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 }
 
 async fn create_token(
-    contract: &Contract,
+    factory: &Contract,
     token_owner_account: &Account,
     alice_account: &Account,
     bob_account: &Account,
@@ -76,48 +76,55 @@ async fn create_token(
     };
 
     // Getting required deposit based on provided arguments
-    let required_deposit: U128 = contract
+    let required_deposit: U128 = factory
         .view("get_required")
         .args_json(json!({"args": token_args}))
         .await?
         .json()?;
 
     // Creating token with less than required deposit (should fail)
-    let res_0 = contract
-        .call("create_token")
+    let not_enough = alice_account
+        .call(factory.id(), "create_token")
         .args_json(json!({"args": token_args}))
         .max_gas()
         .deposit(NearToken::from_yoctonear(required_deposit.0 - 1))
         .transact()
         .await?;
-    assert!(res_0.is_failure());
+    assert!(not_enough.is_failure());
 
     // Creating token with the required deposit
-    let res_1 = contract
-        .call("create_token")
+    let alice_succeeds = alice_account
+        .call(factory.id(), "create_token")
         .args_json(json!({"args": token_args}))
         .max_gas()
         .deposit(NearToken::from_yoctonear(required_deposit.0))
         .transact()
         .await?;
+    assert!(alice_succeeds.json::<bool>()? == true);
 
-    println!("{:?}", required_deposit);
-    assert!(res_1.is_success());
+    // Creating same token fails
+    let bob_balance = bob_account.view_account().await?.balance;
 
-    // Creating token with the required deposit
-    let res_3 = contract
-        .call("create_token")
+    let bob_fails = bob_account
+        .call(factory.id(), "create_token")
         .args_json(json!({"args": token_args}))
         .max_gas()
         .deposit(NearToken::from_yoctonear(required_deposit.0))
         .transact()
         .await?;
 
-    println!("{:?}", required_deposit);
-    assert!(res_3.is_failure());
+    let bob_balance_after = bob_account.view_account().await?.balance;
+    let rest = bob_balance.saturating_sub(bob_balance_after).as_millinear();
+    println!("{:?}", rest);
+
+    // bob fails
+    assert!(bob_fails.json::<bool>()? == false);
+
+    // but it gets back the money (i.e. looses less than 0.005 N)
+    assert!(rest < 5);
 
     // Checking created token account and metadata
-    let token_account_id: AccountId = format!("{}.{}", token_id, contract.id()).parse().unwrap();
+    let token_account_id: AccountId = format!("{}.{}", token_id, factory.id()).parse().unwrap();
     let token_metadata: FungibleTokenMetadata = token_owner_account
         .view(&token_account_id, "ft_metadata")
         .args_json(json!({}))