Error Numbers (#25)

* fix param types in burnable and mintable traits

* fungible example with our our traits

* fungible example with TokenInterface

* typo

* improve docs

* typo

* assign meaningful numbers in error enums

* typo

* remove redundant over- and underflow checks

contracts/token/fungible/src/extensions/burnable/test.rs

@@ -47,7 +47,7 @@ fn burn_with_allowance_works() {
 }
 
 #[test]
-#[should_panic(expected = "Error(Contract, #1)")]
+#[should_panic(expected = "Error(Contract, #200)")]
 fn burn_with_insufficient_balance_panics() {
     let e = Env::default();
     e.mock_all_auths();
@@ -62,7 +62,7 @@ fn burn_with_insufficient_balance_panics() {
 }
 
 #[test]
-#[should_panic(expected = "Error(Contract, #2)")]
+#[should_panic(expected = "Error(Contract, #201)")]
 fn burn_with_no_allowance_panics() {
     let e = Env::default();
     e.mock_all_auths();
@@ -78,7 +78,7 @@ fn burn_with_no_allowance_panics() {
 }
 
 #[test]
-#[should_panic(expected = "Error(Contract, #2)")]
+#[should_panic(expected = "Error(Contract, #201)")]
 fn burn_with_insufficient_allowance_panics() {
     let e = Env::default();
     e.mock_all_auths();

contracts/token/fungible/src/fungible.rs

@@ -182,13 +182,19 @@ pub trait FungibleToken {
 pub enum FungibleTokenError {
     /// Indicates an error related to the current balance of account from which
     /// tokens are expected to be transferred.
-    InsufficientBalance = 1,
+    InsufficientBalance = 200,
     /// Indicates a failure with the allowance mechanism when a given spender
     /// doesn't have enough allowance.
-    InsufficientAllowance = 2,
+    InsufficientAllowance = 201,
     /// Indicates an invalid value for `live_until_ledger` when setting an
     /// allowance.
-    InvalidLiveUntilLedger = 3,
+    InvalidLiveUntilLedger = 202,
+    /// Indicates an error when an input that must be >= 0
+    LessThanZero = 203,
+    /// Indicates an error when an input that must be > 0
+    LessThanOrEqualToZero = 204,
+    /// Indicates overflow when adding two values
+    MathOverflow = 205,
 }
 
 // ################## EVENTS ##################

contracts/token/fungible/src/storage.rs

@@ -161,6 +161,7 @@ pub fn approve(e: &Env, owner: &Address, spender: &Address, amount: i128, live_u
 /// * [`FungibleTokenError::InvalidLiveUntilLedger`] - Occurs when attempting to
 ///   set `live_until_ledger` that is less than the current ledger number and
 ///   greater than `0`.
+/// * [`FungibleTokenError::LessThanZero`] - Occurs when `amount < 0`.
 ///
 /// # Events
 ///
@@ -180,7 +181,7 @@ pub fn set_allowance(
     emit: bool,
 ) {
     if amount < 0 {
-        panic!("amount cannot be negative")
+        panic_with_error!(e, FungibleTokenError::LessThanZero)
     }
 
     let allowance = AllowanceData { amount, live_until_ledger };
@@ -346,13 +347,15 @@ pub fn do_transfer(e: &Env, from: &Address, to: &Address, amount: i128) {
 ///
 /// * [`FungibleTokenError::InsufficientBalance`] - When attempting to transfer
 ///   more tokens than `from` current balance.
+/// * [`FungibleTokenError::LessThanOrEqualToZero`] - When `amount <= 0`.
+/// * [`FungibleTokenError::MathOverflow`] - When `total_supply` overflows.
 ///
 /// # Notes
 ///
 /// No authorization is required.
 pub fn update(e: &Env, from: Option<&Address>, to: Option<&Address>, amount: i128) {
     if amount <= 0 {
-        panic!("amount must be > 0")
+        panic_with_error!(e, FungibleTokenError::LessThanOrEqualToZero)
     }
 
     if let Some(account) = from {
@@ -365,17 +368,21 @@ pub fn update(e: &Env, from: Option<&Address>, to: Option<&Address>, amount: i12
         e.storage().persistent().set(&StorageKey::Balance(account.clone()), &from_balance);
     } else {
         let mut total_supply = total_supply(e);
-        total_supply = total_supply.checked_add(amount).expect("total_supply overflow");
+        total_supply = match total_supply.checked_add(amount) {
+            Some(num) => num,
+            _ => panic_with_error!(e, FungibleTokenError::MathOverflow),
+        };
         e.storage().instance().set(&StorageKey::TotalSupply, &total_supply);
     }
 
     if let Some(account) = to {
-        let mut to_balance = balance(e, account);
-        to_balance = to_balance.checked_add(amount).expect("to_balance overflow");
+        // NOTE: can't overflow because balance + amoount is at most total_supply.
+        let to_balance = balance(e, account) + amount;
         e.storage().persistent().set(&StorageKey::Balance(account.clone()), &to_balance);
     } else {
-        let mut total_supply = total_supply(e);
-        total_supply = total_supply.checked_sub(amount).expect("total_supply underflow");
+        // NOTE: can't overflow because amount <= total_supply or amount <= from_balance
+        // <= total_supply.
+        let total_supply = total_supply(e) - amount;
         e.storage().instance().set(&StorageKey::TotalSupply, &total_supply);
     }
 }

contracts/token/fungible/src/test.rs

@@ -132,7 +132,7 @@ fn spend_allowance_reduces_amount() {
 }
 
 #[test]
-#[should_panic(expected = "Error(Contract, #2)")]
+#[should_panic(expected = "Error(Contract, #201)")]
 fn spend_allowance_insufficient_allowance_fails() {
     let e = Env::default();
     e.mock_all_auths();
@@ -147,7 +147,7 @@ fn spend_allowance_insufficient_allowance_fails() {
 }
 
 #[test]
-#[should_panic(expected = "Error(Contract, #3)")]
+#[should_panic(expected = "Error(Contract, #202)")]
 fn set_allowance_with_expired_ledger_fails() {
     let e = Env::default();
     let address = e.register(MockContract, ());
@@ -160,6 +160,19 @@ fn set_allowance_with_expired_ledger_fails() {
     });
 }
 
+#[test]
+#[should_panic(expected = "Error(Contract, #203)")]
+fn set_allowance_with_neg_amount_fails() {
+    let e = Env::default();
+    let address = e.register(MockContract, ());
+    let owner = Address::generate(&e);
+    let spender = Address::generate(&e);
+
+    e.as_contract(&address, || {
+        set_allowance(&e, &owner, &spender, -1, 5, true);
+    });
+}
+
 #[test]
 fn set_allowance_with_zero_amount() {
     let e = Env::default();
@@ -249,7 +262,7 @@ fn approve_and_transfer_from() {
 }
 
 #[test]
-#[should_panic(expected = "Error(Contract, #1)")]
+#[should_panic(expected = "Error(Contract, #200)")]
 fn transfer_insufficient_balance_fails() {
     let e = Env::default();
     e.mock_all_auths();
@@ -264,7 +277,7 @@ fn transfer_insufficient_balance_fails() {
 }
 
 #[test]
-#[should_panic(expected = "Error(Contract, #2)")]
+#[should_panic(expected = "Error(Contract, #201)")]
 fn transfer_from_insufficient_allowance_fails() {
     let e = Env::default();
     e.mock_all_auths();
@@ -323,7 +336,7 @@ fn update_burns_tokens() {
 }
 
 #[test]
-#[should_panic(expected = "amount must be > 0")]
+#[should_panic(expected = "Error(Contract, #204)")]
 fn update_with_invalid_amount_panics() {
     let e = Env::default();
     let address = e.register(MockContract, ());
@@ -336,7 +349,20 @@ fn update_with_invalid_amount_panics() {
 }
 
 #[test]
-#[should_panic(expected = "Error(Contract, #1)")]
+#[should_panic(expected = "Error(Contract, #205)")]
+fn update_overflow_panics() {
+    let e = Env::default();
+    let address = e.register(MockContract, ());
+    let account = Address::generate(&e);
+
+    e.as_contract(&address, || {
+        mint(&e, &account, i128::MAX);
+        update(&e, None, Some(&account), 1);
+    });
+}
+
+#[test]
+#[should_panic(expected = "Error(Contract, #200)")]
 fn update_with_insufficient_balance_panics() {
     let e = Env::default();
     let address = e.register(MockContract, ());

contracts/token/fungible/test_snapshots/test/set_allowance_with_neg_amount_fails.1.json

@@ -0,0 +1,75 @@
+{
+  "generators": {
+    "address": 3,
+    "nonce": 0
+  },
+  "auth": [
+    []
+  ],
+  "ledger": {
+    "protocol_version": 22,
+    "sequence_number": 0,
+    "timestamp": 0,
+    "network_id": "0000000000000000000000000000000000000000000000000000000000000000",
+    "base_reserve": 0,
+    "min_persistent_entry_ttl": 4096,
+    "min_temp_entry_ttl": 16,
+    "max_entry_ttl": 6312000,
+    "ledger_entries": [
+      [
+        {
+          "contract_data": {
+            "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+            "key": "ledger_key_contract_instance",
+            "durability": "persistent"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_data": {
+                "ext": "v0",
+                "contract": "CAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD2KM",
+                "key": "ledger_key_contract_instance",
+                "durability": "persistent",
+                "val": {
+                  "contract_instance": {
+                    "executable": {
+                      "wasm": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+                    },
+                    "storage": null
+                  }
+                }
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ],
+      [
+        {
+          "contract_code": {
+            "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        },
+        [
+          {
+            "last_modified_ledger_seq": 0,
+            "data": {
+              "contract_code": {
+                "ext": "v0",
+                "hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+                "code": ""
+              }
+            },
+            "ext": "v0"
+          },
+          4095
+        ]
+      ]
+    ]
+  },
+  "events": []
+}