lang: Allow CPI return values (#1598)

.github/workflows/tests.yaml

@@ -329,6 +329,8 @@ jobs:
             path: tests/custom-coder
           - cmd: cd tests/validator-clone && yarn --frozen-lockfile && anchor test --skip-lint
             path: tests/validator-clone
+          - cmd: cd tests/cpi-returns && anchor test --skip-lint
+            path: tests/cpi-returns
     steps:
       - uses: actions/checkout@v2
       - uses: ./.github/actions/setup/

CHANGELOG.md

@@ -12,6 +12,7 @@ The minor version will be incremented upon a breaking change and the patch versi
 
 ### Features
 
+* lang: Add return values to CPI client. ([#1598](https://github.com/project-serum/anchor/pull/1598)).
 * avm: New `avm update` command to update the Anchor CLI to the latest version ([#1670](https://github.com/project-serum/anchor/pull/1670)).
 
 ### Fixes

lang/syn/src/codegen/program/cpi.rs

@@ -2,7 +2,7 @@ use crate::codegen::program::common::{generate_ix_variant, sighash, SIGHASH_GLOB
 use crate::Program;
 use crate::StateIx;
 use heck::SnakeCase;
-use quote::quote;
+use quote::{quote, ToTokens};
 
 pub fn generate(program: &Program) -> proc_macro2::TokenStream {
     // Generate cpi methods for the state struct.
@@ -70,11 +70,20 @@ pub fn generate(program: &Program) -> proc_macro2::TokenStream {
                 let sighash_arr = sighash(SIGHASH_GLOBAL_NAMESPACE, name);
                 let sighash_tts: proc_macro2::TokenStream =
                     format!("{:?}", sighash_arr).parse().unwrap();
+                let ret_type = &ix.returns.ty.to_token_stream();
+                let (method_ret, maybe_return) = match ret_type.to_string().as_str() {
+                    "()" => (quote! {anchor_lang::Result<()> }, quote! { Ok(()) }),
+                    _ => (
+                        quote! { anchor_lang::Result<crate::cpi::Return::<#ret_type>> },
+                        quote! { Ok(crate::cpi::Return::<#ret_type> { phantom: crate::cpi::PhantomData }) }
+                    )
+                };
+
                 quote! {
                     pub fn #method_name<'a, 'b, 'c, 'info>(
                         ctx: anchor_lang::context::CpiContext<'a, 'b, 'c, 'info, #accounts_ident<'info>>,
                         #(#args),*
-                    ) -> anchor_lang::Result<()> {
+                    ) -> #method_ret {
                         let ix = {
                             let ix = instruction::#ix_variant;
                             let mut ix_data = AnchorSerialize::try_to_vec(&ix)
@@ -93,7 +102,11 @@ pub fn generate(program: &Program) -> proc_macro2::TokenStream {
                             &ix,
                             &acc_infos,
                             ctx.signer_seeds,
-                        ).map_err(Into::into)
+                        ).map_or_else(
+                            |e| Err(Into::into(e)),
+                            // Maybe handle Solana return data.
+                            |_| { #maybe_return }
+                        )
                     }
                 }
             };
@@ -108,13 +121,25 @@ pub fn generate(program: &Program) -> proc_macro2::TokenStream {
         #[cfg(feature = "cpi")]
         pub mod cpi {
             use super::*;
+            use std::marker::PhantomData;
 
             pub mod state {
                 use super::*;
 
                 #(#state_cpi_methods)*
             }
 
+            pub struct Return<T> {
+                phantom: std::marker::PhantomData<T>
+            }
+
+            impl<T: AnchorDeserialize> Return<T> {
+                pub fn get(&self) -> T {
+                    let (_key, data) = anchor_lang::solana_program::program::get_return_data().unwrap();
+                    T::try_from_slice(&data).unwrap()
+                }
+            }
+
             #(#global_cpi_methods)*
 
             #accounts

lang/syn/src/codegen/program/handlers.rs

@@ -1,7 +1,7 @@
 use crate::codegen::program::common::*;
 use crate::{Program, State};
 use heck::CamelCase;
-use quote::quote;
+use quote::{quote, ToTokens};
 
 // Generate non-inlined wrappers for each instruction handler, since Solana's
 // BPF max stack size can't handle reasonable sized dispatch trees without doing
@@ -694,6 +694,13 @@ pub fn generate(program: &Program) -> proc_macro2::TokenStream {
             let anchor = &ix.anchor_ident;
             let variant_arm = generate_ix_variant(ix.raw_method.sig.ident.to_string(), &ix.args);
             let ix_name_log = format!("Instruction: {}", ix_name);
+            let ret_type = &ix.returns.ty.to_token_stream();
+            let maybe_set_return_data = match ret_type.to_string().as_str() {
+                "()" => quote! {},
+                _ => quote! {
+                    anchor_lang::solana_program::program::set_return_data(&result.try_to_vec().unwrap());
+                },
+            };
             quote! {
                 #[inline(never)]
                 pub fn #ix_method_name(
@@ -722,7 +729,7 @@ pub fn generate(program: &Program) -> proc_macro2::TokenStream {
                     )?;
 
                     // Invoke user defined handler.
-                    #program_name::#ix_method_name(
+                    let result = #program_name::#ix_method_name(
                         anchor_lang::context::Context::new(
                             program_id,
                             &mut accounts,
@@ -732,6 +739,9 @@ pub fn generate(program: &Program) -> proc_macro2::TokenStream {
                         #(#ix_arg_names),*
                     )?;
 
+                    // Maybe set Solana return data.
+                    #maybe_set_return_data
+
                     // Exit routine.
                     accounts.exit(program_id)
                 }

lang/syn/src/idl/file.rs

@@ -66,6 +66,7 @@ pub fn parse(
                                     name,
                                     accounts,
                                     args,
+                                    returns: None,
                                 }
                             })
                             .collect::<Vec<_>>()
@@ -105,6 +106,7 @@ pub fn parse(
                         name,
                         accounts,
                         args,
+                        returns: None,
                     }
                 };
 
@@ -164,10 +166,16 @@ pub fn parse(
             // todo: don't unwrap
             let accounts_strct = accs.get(&ix.anchor_ident.to_string()).unwrap();
             let accounts = idl_accounts(&ctx, accounts_strct, &accs, seeds_feature);
+            let ret_type_str = ix.returns.ty.to_token_stream().to_string();
+            let returns = match ret_type_str.as_str() {
+                "()" => None,
+                _ => Some(ret_type_str.parse().unwrap()),
+            };
             IdlInstruction {
                 name: ix.ident.to_string().to_mixed_case(),
                 accounts,
                 args,
+                returns,
             }
         })
         .collect::<Vec<_>>();

lang/syn/src/idl/mod.rs

@@ -45,6 +45,7 @@ pub struct IdlInstruction {
     pub name: String,
     pub accounts: Vec<IdlAccountItem>,
     pub args: Vec<IdlField>,
+    pub returns: Option<IdlType>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]

lang/syn/src/lib.rs

@@ -14,7 +14,7 @@ use syn::spanned::Spanned;
 use syn::token::Comma;
 use syn::{
     Expr, Generics, Ident, ImplItemMethod, ItemEnum, ItemFn, ItemImpl, ItemMod, ItemStruct, LitInt,
-    LitStr, PatType, Token, TypePath,
+    LitStr, PatType, Token, Type, TypePath,
 };
 
 pub mod codegen;
@@ -85,6 +85,7 @@ pub struct Ix {
     pub raw_method: ItemFn,
     pub ident: Ident,
     pub args: Vec<IxArg>,
+    pub returns: IxReturn,
     // The ident for the struct deriving Accounts.
     pub anchor_ident: Ident,
 }
@@ -95,6 +96,11 @@ pub struct IxArg {
     pub raw_arg: PatType,
 }
 
+#[derive(Debug)]
+pub struct IxReturn {
+    pub ty: Type,
+}
+
 #[derive(Debug)]
 pub struct FallbackFn {
     raw_method: ItemFn,

lang/syn/src/parser/program/instructions.rs

@@ -1,5 +1,5 @@
 use crate::parser::program::ctx_accounts_ident;
-use crate::{FallbackFn, Ix, IxArg};
+use crate::{FallbackFn, Ix, IxArg, IxReturn};
 use syn::parse::{Error as ParseError, Result as ParseResult};
 use syn::spanned::Spanned;
 
@@ -23,12 +23,14 @@ pub fn parse(program_mod: &syn::ItemMod) -> ParseResult<(Vec<Ix>, Option<Fallbac
         })
         .map(|method: &syn::ItemFn| {
             let (ctx, args) = parse_args(method)?;
+            let returns = parse_return(method)?;
             let anchor_ident = ctx_accounts_ident(&ctx.raw_arg)?;
             Ok(Ix {
                 raw_method: method.clone(),
                 ident: method.sig.ident.clone(),
                 args,
                 anchor_ident,
+                returns,
             })
         })
         .collect::<ParseResult<Vec<Ix>>>()?;
@@ -91,3 +93,34 @@ pub fn parse_args(method: &syn::ItemFn) -> ParseResult<(IxArg, Vec<IxArg>)> {
 
     Ok((ctx, args))
 }
+
+pub fn parse_return(method: &syn::ItemFn) -> ParseResult<IxReturn> {
+    match method.sig.output {
+        syn::ReturnType::Type(_, ref ty) => {
+            let ty = match ty.as_ref() {
+                syn::Type::Path(ty) => ty,
+                _ => return Err(ParseError::new(ty.span(), "expected a return type")),
+            };
+            // Assume unit return by default
+            let default_generic_arg = syn::GenericArgument::Type(syn::parse_str("()").unwrap());
+            let generic_args = match &ty.path.segments.last().unwrap().arguments {
+                syn::PathArguments::AngleBracketed(params) => params.args.iter().last().unwrap(),
+                _ => &default_generic_arg,
+            };
+            let ty = match generic_args {
+                syn::GenericArgument::Type(ty) => ty.clone(),
+                _ => {
+                    return Err(ParseError::new(
+                        ty.span(),
+                        "expected generic return type to be a type",
+                    ))
+                }
+            };
+            Ok(IxReturn { ty })
+        }
+        _ => Err(ParseError::new(
+            method.sig.output.span(),
+            "expected a return type",
+        )),
+    }
+}

tests/cpi-returns/.gitignore

@@ -0,0 +1,6 @@
+
+.anchor
+.DS_Store
+target
+**/*.rs.bk
+node_modules

tests/cpi-returns/Anchor.toml

@@ -0,0 +1,16 @@
+[features]
+seeds = false
+
+[programs.localnet]
+callee = "Fg6PaFpoGXkYsidMpWTK6W2BeZ7FEfcYkg476zPFsLnS"
+caller = "HmbTLCmaGvZhKnn1Zfa1JVnp7vkMV4DYVxPLWBVoN65L"
+
+[registry]
+url = "https://anchor.projectserum.com"
+
+[provider]
+cluster = "localnet"
+wallet = "~/.config/solana/id.json"
+
+[scripts]
+test = "yarn run ts-mocha -p ./tsconfig.json -t 1000000 tests/**/*.ts"

tests/cpi-returns/Cargo.toml

@@ -0,0 +1,4 @@
+[workspace]
+members = [
+    "programs/*"
+]

tests/cpi-returns/migrations/deploy.ts

@@ -0,0 +1,12 @@
+// Migrations are an early feature. Currently, they're nothing more than this
+// single deploy script that's invoked from the CLI, injecting a provider
+// configured from the workspace's Anchor.toml.
+
+const anchor = require("@project-serum/anchor");
+
+module.exports = async function (provider) {
+  // Configure client to use the provider.
+  anchor.setProvider(provider);
+
+  // Add your deploy script here.
+};

tests/cpi-returns/package.json

@@ -0,0 +1,19 @@
+{
+  "name": "cpi-returns",
+  "version": "0.23.0",
+  "license": "(MIT OR Apache-2.0)",
+  "homepage": "https://github.com/project-serum/anchor#readme",
+  "bugs": {
+    "url": "https://github.com/project-serum/anchor/issues"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/project-serum/anchor.git"
+  },
+  "engines": {
+    "node": ">=11"
+  },
+  "scripts": {
+    "test": "anchor run test-with-build"
+  }
+}

tests/cpi-returns/programs/callee/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "callee"
+version = "0.1.0"
+description = "Created with Anchor"
+edition = "2018"
+
+[lib]
+crate-type = ["cdylib", "lib"]
+name = "callee"
+
+[features]
+no-entrypoint = []
+no-idl = []
+no-log-ix-name = []
+cpi = ["no-entrypoint"]
+default = []
+
+[dependencies]
+anchor-lang = { path = "../../../../lang", features = ["init-if-needed"] }

tests/cpi-returns/programs/callee/Xargo.toml

@@ -0,0 +1,2 @@
+[target.bpfel-unknown-unknown.dependencies.std]
+features = []

tests/cpi-returns/programs/callee/src/lib.rs

@@ -0,0 +1,50 @@
+use anchor_lang::prelude::*;
+
+declare_id!("Fg6PaFpoGXkYsidMpWTK6W2BeZ7FEfcYkg476zPFsLnS");
+
+#[program]
+pub mod callee {
+    use super::*;
+
+    #[derive(AnchorSerialize, AnchorDeserialize)]
+    pub struct StructReturn {
+        pub value: u64,
+    }
+
+    pub fn initialize(_ctx: Context<Initialize>) -> Result<()> {
+        Ok(())
+    }
+
+    pub fn return_u64(_ctx: Context<CpiReturn>) -> Result<u64> {
+        Ok(10)
+    }
+
+    pub fn return_struct(_ctx: Context<CpiReturn>) -> Result<StructReturn> {
+        let s = StructReturn { value: 11 };
+        Ok(s)
+    }
+
+    pub fn return_vec(_ctx: Context<CpiReturn>) -> Result<Vec<u8>> {
+        Ok(vec![12, 13, 14, 100])
+    }
+}
+
+#[derive(Accounts)]
+pub struct Initialize<'info> {
+    #[account(init, payer = user, space = 8 + 8)]
+    pub account: Account<'info, CpiReturnAccount>,
+    #[account(mut)]
+    pub user: Signer<'info>,
+    pub system_program: Program<'info, System>,
+}
+
+#[derive(Accounts)]
+pub struct CpiReturn<'info> {
+    #[account(mut)]
+    pub account: Account<'info, CpiReturnAccount>,
+}
+
+#[account]
+pub struct CpiReturnAccount {
+    pub value: u64,
+}