Add demonstration how to mock transferred_balance (#555)

* [chores] implicitely ➜ implicitly

* [examples] Add demonstration of how to mock transferred_balance

* [lang] Fix clippy 'needless_lifetimes'

Error was:

explicit lifetimes given in parameter types where they could
be elided (or replaced with `'_` if needed by type declaration)

* [lang] Apply cargo fmt

* [examples] Fix param

RELEASES.md

@@ -357,7 +357,7 @@ We won't be going into the details for any of those but will briefly present the
 | `#[ink(topic)]` | Applicate on ink! event field. | Tells the ink! codegen to provide a topic hash for the given field. Every ink! event can only have a limited number of such topic field. Similar semantics as to indexed event arguments in Solidity. |
 | `#[ink(message)]` | Applicable to methods. | Flags a method for the ink! storage struct as message making it available to the API for calling the contract. |
 | `#[ink(constructor)]` | Applicable to method. | Flags a method for the ink! storage struct as constructor making it available to the API for instantiating the contract. |
-| `#[ink(payable)]` **new** | Applicable to ink! messages. | Allows receiving value as part of the call of the ink! message. ink! constructors are implicitely payable. |
+| `#[ink(payable)]` **new** | Applicable to ink! messages. | Allows receiving value as part of the call of the ink! message. ink! constructors are implicitly payable. |
 | `#[ink(selector = "..")]` **new** | Applicable to ink! messages and ink! constructors. | Specifies a concrete dispatch selector for the flagged entity. This allows a contract author to precisely control the selectors of their APIs making it possible to rename their API without breakage. |
 | `#[ink(namespace = "..")]` **new** | Applicable to ink! trait implementation blocks. | Changes the resulting selectors of all the ink! messages and ink! constructors within the trait implementation. Allows to disambiguate between trait implementations with overlapping message or constructor names. Use only with great care and consideration! |
 | `#[ink(implementation)]` **new** | Applicable to ink! implementation blocks. | Tells the ink! codegen that some implementation block shall be granted access to ink! internals even without it containing any ink! messages or ink! constructors. |

crates/lang/codegen/src/generator/metadata.rs

@@ -88,9 +88,9 @@ impl Metadata<'_> {
     }
 
     /// Extracts the doc strings from the given slice of attributes.
-    fn extract_doc_comments<'a>(
-        attributes: &'a [syn::Attribute],
-    ) -> impl Iterator<Item = String> + 'a {
+    fn extract_doc_comments(
+        attributes: &[syn::Attribute],
+    ) -> impl Iterator<Item = String> + '_ {
         attributes
             .iter()
             .filter_map(|attribute| {
@@ -109,7 +109,7 @@ impl Metadata<'_> {
     }
 
     /// Generates ink! metadata for all contract constructors.
-    fn generate_constructors<'a>(&'a self) -> impl Iterator<Item = TokenStream2> + 'a {
+    fn generate_constructors(&self) -> impl Iterator<Item = TokenStream2> + '_ {
         self.contract
             .module()
             .impls()
@@ -200,7 +200,7 @@ impl Metadata<'_> {
         }
     }
 
-    fn generate_messages<'a>(&'a self) -> impl Iterator<Item = TokenStream2> + 'a {
+    fn generate_messages(&self) -> impl Iterator<Item = TokenStream2> + '_ {
         self.contract
             .module()
             .impls()
@@ -272,7 +272,7 @@ impl Metadata<'_> {
     }
 
     /// Generates ink! metadata for all user provided ink! event definitions.
-    fn generate_events<'a>(&'a self) -> impl Iterator<Item = TokenStream2> + 'a {
+    fn generate_events(&self) -> impl Iterator<Item = TokenStream2> + '_ {
         self.contract.module().events().map(|event| {
             let span = event.span();
             let ident = event.ident();
@@ -293,9 +293,7 @@ impl Metadata<'_> {
     }
 
     /// Generate ink! metadata for a single argument of an ink! event definition.
-    fn generate_event_args<'a>(
-        event: &'a ir::Event,
-    ) -> impl Iterator<Item = TokenStream2> + 'a {
+    fn generate_event_args(event: &ir::Event) -> impl Iterator<Item = TokenStream2> + '_ {
         event.fields().map(|event_field| {
             let span = event_field.span();
             let ident = event_field.ident();
@@ -317,7 +315,7 @@ impl Metadata<'_> {
     }
 
     /// Generates the documentation for the contract module.
-    fn generate_docs<'a>(&'a self) -> impl Iterator<Item = String> + 'a {
+    fn generate_docs(&self) -> impl Iterator<Item = String> + '_ {
         Self::extract_doc_comments(self.contract.module().attrs())
     }
 }

examples/contract-transfer/lib.rs

@@ -75,6 +75,18 @@ pub mod give_me {
                     }
                 })
         }
+
+        /// Returns `true` if the token amount which the contract received
+        /// with this call is exactly `10`.
+        ///
+        /// # Note
+        ///
+        /// The method needs to be annotated with `payable`; only then it is
+        /// allowed to receive value as part of the call.
+        #[ink(message, payable, selector = "0xCAFEBABE")]
+        pub fn was_it_ten(&mut self) -> bool {
+            self.env().transferred_balance() == 10
+        }
     }
 
     #[cfg(test)]
@@ -118,20 +130,51 @@ pub mod give_me {
             assert_eq!(ret, Err(Error::InsufficientFunds));
         }
 
+        #[ink::test]
+        fn test_transferred_value() {
+            // given
+            let accounts = default_accounts();
+            let mut give_me = create_contract(100);
+
+            // when
+            set_sender(accounts.eve);
+            let mut data = ink_env::test::CallData::new(ink_env::call::Selector::new([
+                0xCA, 0xFE, 0xBA, 0xBE,
+            ]));
+            data.push_arg(&accounts.eve);
+            let mock_transferred_balance = 10;
+
+            // Push the new execution context which sets Eve as caller and
+            // the `mock_transferred_balance` as the value which the contract
+            // will see as transferred to it.
+            ink_env::test::push_execution_context::<ink_env::DefaultEnvironment>(
+                accounts.eve,
+                contract_id(),
+                1000000,
+                mock_transferred_balance,
+                data,
+            );
+
+            // then
+            assert_eq!(give_me.was_it_ten(), true);
+        }
+
         /// Creates a new instance of `GiveMe` with `initial_balance`.
         ///
         /// Returns the `contract_instance`.
         fn create_contract(initial_balance: Balance) -> GiveMe {
             let accounts = default_accounts();
-            let contract_id = ink_env::test::get_current_contract_account_id::<
-                ink_env::DefaultEnvironment,
-            >()
-            .expect("Cannot get contract id");
             set_sender(accounts.alice);
-            set_balance(contract_id, initial_balance);
+            set_balance(contract_id(), initial_balance);
             GiveMe::new()
         }
 
+        fn contract_id() -> AccountId {
+            ink_env::test::get_current_contract_account_id::<ink_env::DefaultEnvironment>(
+            )
+            .expect("Cannot get contract id")
+        }
+
         fn set_sender(sender: AccountId) {
             let callee = ink_env::account_id::<ink_env::DefaultEnvironment>()
                 .unwrap_or([0x0; 32].into());