Allow mutable parameters in messages

.config/cargo_spellcheck.dic

@@ -52,6 +52,7 @@ fuzzer
 getter
 growable
 ident
+idents
 interoperate
 invariants
 kB

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Added
+- Allow mutable parameters in messages - [#2004](https://github.com/paritytech/ink/pull/2004)
 - [E2E] Allow testing with live-chain state - [#1949](https://github.com/paritytech/ink/pull/1949)
 - [E2E] Call builders and extra gas margin option - [#1917](https://github.com/paritytech/ink/pull/1917)
 - Linter: `storage_never_freed` lint - [#1932](https://github.com/paritytech/ink/pull/1932)

crates/ink/codegen/src/generator/arg_list.rs

@@ -28,7 +28,8 @@ pub fn output_ident(message_name: &syn::Ident) -> syn::Ident {
     format_ident!("{}Output", message_name.to_string().to_lower_camel_case())
 }
 
-/// Returns the sequence of artificial input parameter bindings for the message.
+/// Returns the sequence of artificial input parameter bindings
+/// for the message or constructor.
 ///
 /// # Note
 ///
@@ -46,6 +47,22 @@ pub fn input_types(inputs: ir::InputsIter) -> Vec<&syn::Type> {
     inputs.map(|pat_type| &*pat_type.ty).collect::<Vec<_>>()
 }
 
+/// Returns the sequence of input idents for the message.
+pub fn input_message_idents(inputs: ir::InputsIter) -> Vec<&syn::Ident> {
+    inputs
+        .map(|input| {
+            match &*input.pat {
+                syn::Pat::Ident(ident) => &ident.ident,
+                _ => {
+                    unreachable!(
+                        "encountered ink! dispatch input with missing identifier"
+                    )
+                }
+            }
+        })
+        .collect::<Vec<_>>()
+}
+
 /// Returns a tuple type representing the types yielded by the input types.
 pub fn input_types_tuple(inputs: ir::InputsIter) -> TokenStream2 {
     let input_types = input_types(inputs);

crates/ink/codegen/src/generator/as_dependency/contract_ref.rs

@@ -289,7 +289,7 @@ impl ContractRef<'_> {
             ir::Receiver::RefMut => quote! { forward_mut },
         };
         let mut_token = message.receiver().is_ref_mut().then(|| quote! { mut });
-        let input_bindings = message.inputs().map(|input| &input.pat).collect::<Vec<_>>();
+        let input_idents = generator::input_message_idents(message.inputs());
         let input_types = message.inputs().map(|input| &input.ty).collect::<Vec<_>>();
         let cfg_attrs = message.get_cfg_attrs(span);
         quote_spanned!(span=>
@@ -301,13 +301,13 @@ impl ContractRef<'_> {
             #( #cfg_attrs )*
             fn #message_ident(
                 & #mut_token self
-                #( , #input_bindings : #input_types )*
+                #( , #input_idents : #input_types )*
             ) -> Self::#output_ident {
                 <_ as #trait_path>::#message_ident(
                     <_ as ::ink::codegen::TraitCallForwarderFor<{#trait_info_id}>>::#forward_operator(
                         <Self as ::ink::codegen::TraitCallBuilder>::#call_operator(self),
                     )
-                    #( , #input_bindings )*
+                    #( , #input_idents )*
                 )
             }
         )
@@ -384,7 +384,7 @@ impl ContractRef<'_> {
             ir::Receiver::RefMut => quote! { call_mut },
         };
         let mut_token = message.receiver().is_ref_mut().then(|| quote! { mut });
-        let input_bindings = message.inputs().map(|input| &input.pat).collect::<Vec<_>>();
+        let input_idents = generator::input_message_idents(message.inputs());
         let input_types = message.inputs().map(|input| &input.ty).collect::<Vec<_>>();
         let output_type = message.output().map(|ty| quote! { -> #ty });
         let wrapped_output_type = message.wrapped_output();
@@ -393,9 +393,9 @@ impl ContractRef<'_> {
             #[inline]
             pub fn #message_ident(
                 & #mut_token self
-                #( , #input_bindings : #input_types )*
+                #( , #input_idents : #input_types )*
             ) #output_type {
-                self.#try_message_ident( #( #input_bindings, )* )
+                self.#try_message_ident( #( #input_idents, )* )
                     .unwrap_or_else(|error| ::core::panic!(
                         "encountered error while calling {}::{}: {:?}",
                         ::core::stringify!(#storage_ident),
@@ -408,10 +408,10 @@ impl ContractRef<'_> {
             #[inline]
             pub fn #try_message_ident(
                 & #mut_token self
-                #( , #input_bindings : #input_types )*
+                #( , #input_idents : #input_types )*
             ) -> #wrapped_output_type {
                 <Self as ::ink::codegen::TraitCallBuilder>::#call_operator(self)
-                    .#message_ident( #( #input_bindings ),* )
+                    .#message_ident( #( #input_idents ),* )
                     .try_invoke()
                     .unwrap_or_else(|error| ::core::panic!(
                         "encountered error while calling {}::{}: {:?}",

crates/ink/codegen/src/generator/mod.rs

@@ -48,6 +48,7 @@ pub use self::{
         generate_reference_to_trait_info,
         input_bindings,
         input_bindings_tuple,
+        input_message_idents,
         input_types,
         input_types_tuple,
         output_ident,

crates/ink/ir/src/ir/item_impl/message.rs

@@ -382,13 +382,23 @@ mod tests {
 
     #[test]
     fn inputs_works() {
+        macro_rules! expected_input {
+            ( mut $name:ident: $ty:ty  ) => {{
+                syn::parse_quote! {
+                    mut $name: $ty
+                }
+            }};
+            ( $name:ident: $ty:ty  ) => {{
+                syn::parse_quote! {
+                    $name: $ty
+                }
+            }};
+        }
         macro_rules! expected_inputs {
-            ( $( $name:ident: $ty:ty ),* ) => {{
+            ( $( $($ts:ident)+: $ty:ty ),* ) => {{
                 vec![
                     $(
-                        syn::parse_quote! {
-                            $name: $ty
-                        }
+                        expected_input!($($ts)+: $ty)
                     ),*
                 ]
             }};
@@ -410,12 +420,20 @@ mod tests {
                     fn my_message(&self, a: i32) {}
                 },
             ),
+            (
+                // Single mutable input:
+                expected_inputs!(mut a: i32),
+                syn::parse_quote! {
+                    #[ink(message)]
+                    fn my_message(&self, mut a: i32) {}
+                },
+            ),
             (
                 // Some inputs:
-                expected_inputs!(a: i32, b: u64, c: [u8; 32]),
+                expected_inputs!(a: i32, b: u64, mut c: [u8; 32]),
                 syn::parse_quote! {
                     #[ink(message)]
-                    fn my_message(&self, a: i32, b: u64, c: [u8; 32]) {}
+                    fn my_message(&self, a: i32, b: u64, mut c: [u8; 32]) {}
                 },
             ),
         ];

integration-tests/mother/lib.rs

@@ -19,6 +19,7 @@
 #[ink::contract]
 mod mother {
     use ink::prelude::{
+        format,
         string::{
             String,
             ToString,
@@ -181,6 +182,13 @@ mod mother {
         pub fn debug_log(&mut self, _message: String) {
             ink::env::debug_println!("debug_log: {}", _message);
         }
+
+        /// Mutates the input string to return "Hello, { name }"
+        #[ink(message)]
+        pub fn mut_hello_world(&self, mut message: String) -> String {
+            message = format!("Hello, {}", message);
+            message
+        }
     }
 
     #[cfg(test)]
@@ -227,5 +235,12 @@ mod mother {
             let mut contract = Mother::default();
             let _ = contract.revert_or_trap(Some(Failure::Panic));
         }
+
+        #[ink::test]
+        fn mut_works() {
+            let contract = Mother::default();
+            let res = contract.mut_hello_world("Alice".to_string());
+            assert_eq!("Hello, Alice", res)
+        }
     }
 }