feat(lang): Allow Generic type programs in Accounts Struct (#3878)

* feat(lang): Enhance Program type with generic validation support

* feat(tests): Add generic program tests

* refactor: Replace realloc with resize

* feat(tests): Add test for custom program address validation

* bench: update

* chore: Improve formatting

* Revert "refactor: Replace realloc with resize"

This reverts commit 61cc66d.

* feat(tests): Add custom program tests

* chore(tests): Rename to custom-program

* chore: Update CHANGELOG.md

* chore: Update benchmarks

Author: swaroop-osec

.github/workflows/reusable-tests.yaml

@@ -414,6 +414,8 @@ jobs:
             path: tests/declare-id
           - cmd: cd tests/declare-program && anchor test --skip-lint
             path: tests/declare-program
+          - cmd: cd tests/custom-program && anchor test --skip-lint
+            path: tests/custom-program
           - cmd: cd tests/typescript && anchor test --skip-lint && npx tsc --noEmit
             path: tests/typescript
           # zero-copy tests cause `/usr/bin/ld: final link failed: No space left on device`

CHANGELOG.md

@@ -37,6 +37,7 @@ The minor version will be incremented upon a breaking change and the patch versi
 - cli: Replace `anchor verify` to use `solana-verify` under the hood, adding automatic installation via AVM, local path support, and future-proof argument passing ([#3768](https://github.com/solana-foundation/anchor/pull/3768)).
 - lang: Replace `solana-program` crate with smaller crates ([#3819](https://github.com/solana-foundation/anchor/pull/3819)).
 - cli: Make `anchor deploy` to upload the IDL to the cluster by default unless `--no-idl` is passed ([#3863](https://github.com/solana-foundation/anchor/pull/3863)).
+- lang: Add generic program validation support to `Program` type allowing `Program<'info>` for executable-only validation ([#3878](https://github.com/solana-foundation/anchor/pull/3878)).
 - lang: Use `solana-invoke` instead of `solana_cpi::invoke` ([#3900](https://github.com/solana-foundation/anchor/pull/3900)).
 - client: remove `solana-client` from `anchor-client` and `cli` ([#3877](https://github.com/solana-foundation/anchor/pull/3877)).
 - idl: Build IDL on stable Rustc ([#3842](https://github.com/solana-foundation/anchor/pull/3842)).

bench/COMPUTE_UNITS.md

@@ -286,9 +286,9 @@ Solana version: 2.1.0
 | interface4                  | 1,189         | -                     |
 | interface8                  | 1,748         | -                     |
 | program1                    | 779           | -                     |
-| program2                    | 920           | -                     |
-| program4                    | 1,193         | -                     |
-| program8                    | 1,744         | -                     |
+| program2                    | 934           | 🔴 **+14 (1.52%)**    |
+| program4                    | 1,221         | 🔴 **+28 (2.35%)**    |
+| program8                    | 1,800         | 🔴 **+56 (3.21%)**    |
 | signer1                     | 774           | -                     |
 | signer2                     | 1,064         | -                     |
 | signer4                     | 1,637         | -                     |

lang/src/accounts/program.rs

@@ -21,15 +21,24 @@ use std::ops::Deref;
 ///
 /// # Table of Contents
 /// - [Basic Functionality](#basic-functionality)
+/// - [Generic Program Validation](#generic-program-validation)
 /// - [Out of the Box Types](#out-of-the-box-types)
 ///
 /// # Basic Functionality
 ///
+/// For `Program<'info, T>` where T implements Id:
 /// Checks:
 ///
 /// - `account_info.key == expected_program`
 /// - `account_info.executable == true`
 ///
+/// # Generic Program Validation
+///
+/// For `Program<'info>` (without type parameter):
+/// - Only checks: `account_info.executable == true`
+/// - Use this when you only need to verify that an address is executable,
+///   without validating against a specific program ID.
+///
 /// # Example
 /// ```ignore
 /// #[program]
@@ -65,6 +74,16 @@ use std::ops::Deref;
 /// - `program_data`'s constraint checks that its upgrade authority is the `authority` account.
 /// - Finally, `authority` needs to sign the transaction.
 ///
+/// ## Generic Program Example
+/// ```ignore
+/// #[derive(Accounts)]
+/// pub struct ValidateExecutableProgram<'info> {
+///     // Only validates that the provided account is executable
+///     pub any_program: Program<'info>,
+///     pub authority: Signer<'info>,
+/// }
+/// ```
+///
 /// # Out of the Box Types
 ///
 /// Between the [`anchor_lang`](https://docs.rs/anchor-lang/latest/anchor_lang) and [`anchor_spl`](https://docs.rs/anchor_spl/latest/anchor_spl) crates,
@@ -75,7 +94,7 @@ use std::ops::Deref;
 /// - [`Token`](https://docs.rs/anchor-spl/latest/anchor_spl/token/struct.Token.html)
 ///
 #[derive(Clone)]
-pub struct Program<'info, T> {
+pub struct Program<'info, T = ()> {
     info: &'info AccountInfo<'info>,
     _phantom: PhantomData<T>,
 }
@@ -128,13 +147,15 @@ impl<'a, T: Id> TryFrom<&'a AccountInfo<'a>> for Program<'a, T> {
     type Error = Error;
     /// Deserializes the given `info` into a `Program`.
     fn try_from(info: &'a AccountInfo<'a>) -> Result<Self> {
-        if info.key != &T::id() {
+        // Special handling for unit type () - only check executable, not program ID
+        let is_unit_type = T::id() == Pubkey::default();
+
+        if !is_unit_type && info.key != &T::id() {
             return Err(Error::from(ErrorCode::InvalidProgramId).with_pubkeys((*info.key, T::id())));
         }
         if !info.executable {
             return Err(ErrorCode::InvalidProgramExecutable.into());
         }
-
         Ok(Program::new(info))
     }
 }
@@ -195,3 +216,13 @@ impl<T: AccountDeserialize> Key for Program<'_, T> {
         *self.info.key
     }
 }
+
+// Implement Id trait for unit type to support Program<'info> without type parameter
+impl crate::Id for () {
+    fn id() -> Pubkey {
+        // For generic programs, this should never be called since they don't validate specific program IDs.
+        // However, we need to implement it to satisfy the trait bounds.
+        // Using a special marker value that indicates "any program"
+        Pubkey::default()
+    }
+}

lang/syn/src/idl/accounts.rs

@@ -146,10 +146,17 @@ fn get_address(acc: &Field) -> TokenStream {
     match &acc.ty {
         Ty::Program(_) | Ty::Sysvar(_) => {
             let ty = acc.account_ty();
-            let id_trait = matches!(acc.ty, Ty::Program(_))
-                .then(|| quote!(anchor_lang::Id))
-                .unwrap_or_else(|| quote!(anchor_lang::solana_program::sysvar::SysvarId));
-            quote! { Some(<#ty as #id_trait>::id().to_string()) }
+            // Check if this is the unit type marker (for generic Program<'info>)
+            let ty_str = quote!(#ty).to_string();
+            if ty_str == "" || ty_str == "__SolanaProgramUnitType" {
+                // For generic programs, we don't have a specific address
+                quote! { None }
+            } else {
+                let id_trait = matches!(acc.ty, Ty::Program(_))
+                    .then(|| quote!(anchor_lang::Id))
+                    .unwrap_or_else(|| quote!(anchor_lang::solana_program::sysvar::SysvarId));
+                quote! { Some(<#ty as #id_trait>::id().to_string()) }
+            }
         }
         _ => acc
             .constraints

lang/syn/src/lib.rs

@@ -344,6 +344,20 @@ impl Field {
                     Sysvar<#account>
                 }
             }
+            Ty::Program(ty) => {
+                let program = &ty.account_type_path;
+                // Check if this is the generic Program<'info> (unit type)
+                let program_str = quote!(#program).to_string();
+                if program_str == "__SolanaProgramUnitType" {
+                    quote! {
+                        #container_ty<'info>
+                    }
+                } else {
+                    quote! {
+                        #container_ty<'info, #program>
+                    }
+                }
+            }
             _ => quote! {
                 #container_ty<#account_ty>
             },
@@ -543,8 +557,14 @@ impl Field {
             },
             Ty::Program(ty) => {
                 let program = &ty.account_type_path;
-                quote! {
-                    #program
+                // Check if this is the special marker for generic Program<'info> (unit type)
+                let program_str = quote!(#program).to_string();
+                if program_str == "__SolanaProgramUnitType" {
+                    quote! {}
+                } else {
+                    quote! {
+                        #program
+                    }
                 }
             }
             Ty::Interface(ty) => {

lang/syn/src/parser/accounts/mod.rs

@@ -477,7 +477,7 @@ fn parse_interface_account_ty(path: &syn::Path) -> ParseResult<InterfaceAccountT
 }
 
 fn parse_program_ty(path: &syn::Path) -> ParseResult<ProgramTy> {
-    let account_type_path = parse_account(path)?;
+    let account_type_path = parse_program_account(path)?;
     Ok(ProgramTy { account_type_path })
 }
 
@@ -486,6 +486,52 @@ fn parse_interface_ty(path: &syn::Path) -> ParseResult<InterfaceTy> {
     Ok(InterfaceTy { account_type_path })
 }
 
+// Special parsing function for Program that handles both Program<'info> and Program<'info, T>
+fn parse_program_account(path: &syn::Path) -> ParseResult<syn::TypePath> {
+    let segments = &path.segments[0];
+    match &segments.arguments {
+        syn::PathArguments::AngleBracketed(args) => {
+            match args.args.len() {
+                // Program<'info> - only lifetime, no type parameter
+                1 => {
+                    // Create a special marker for unit type that gets handled later
+                    use syn::{Path, PathSegment, PathArguments};
+                    let path_segment = PathSegment {
+                        ident: syn::Ident::new("__SolanaProgramUnitType", proc_macro2::Span::call_site()),
+                        arguments: PathArguments::None,
+                    };
+
+                    Ok(syn::TypePath {
+                        qself: None,
+                        path: Path {
+                            leading_colon: None,
+                            segments: std::iter::once(path_segment).collect(),
+                        },
+                    })
+                }
+                // Program<'info, T> - lifetime and type
+                2 => {
+                    match &args.args[1] {
+                        syn::GenericArgument::Type(syn::Type::Path(ty_path)) => Ok(ty_path.clone()),
+                        _ => Err(ParseError::new(
+                            args.args[1].span(),
+                            "second bracket argument must be a type",
+                        )),
+                    }
+                }
+                _ => Err(ParseError::new(
+                    args.args.span(),
+                    "Program must have either just a lifetime (Program<'info>) or a lifetime and type (Program<'info, T>)",
+                )),
+            }
+        }
+        _ => Err(ParseError::new(
+            segments.arguments.span(),
+            "expected angle brackets with lifetime or lifetime and type",
+        )),
+    }
+}
+
 // TODO: this whole method is a hack. Do something more idiomatic.
 fn parse_account(mut path: &syn::Path) -> ParseResult<syn::TypePath> {
     let path_str = parser::tts_to_string(path).replace(' ', "");

tests/bench/bench.json

@@ -1380,9 +1380,9 @@
         "interface4": 1189,
         "interface8": 1748,
         "program1": 779,
-        "program2": 920,
-        "program4": 1193,
-        "program8": 1744,
+        "program2": 934,
+        "program4": 1221,
+        "program8": 1800,
         "signer1": 774,
         "signer2": 1064,
         "signer4": 1637,
@@ -1752,9 +1752,9 @@
         "interface4": 1301,
         "interface8": 1867,
         "program1": 890,
-        "program2": 1035,
-        "program4": 1313,
-        "program8": 1879,
+        "program2": 1051,
+        "program4": 1345,
+        "program8": 1943,
         "signer1": 874,
         "signer2": 1173,
         "signer4": 1759,

tests/custom-program/Anchor.toml

@@ -0,0 +1,21 @@
+[provider]
+cluster = "localnet"
+wallet = "~/.config/solana/id.json"
+
+[programs.localnet]
+custom_program = "FdQ5d5kJDidxLP8qBm2d4G47QbDMWk6iWJ3QkYY2UAP7"
+
+[scripts]
+test = "yarn run ts-mocha -t 1000000 tests/*.ts"
+
+[test.validator]
+url = "https://api.mainnet-beta.solana.com"
+ 
+[[test.validator.clone]]
+address = "9cxLzxjrTeodcbaEU3KCNGE1a4yFZEcdJ7uEXN378S4U"
+
+[[test.validator.clone]]
+address = "PhoeNiXZ8ByJGLkxNfZRnkUfjvmuYqLR89jjFHGqdXY"
+
+[[test.validator.clone]]
+address = "dRiftyHA39MWEi3m9aunc5MzRF1JYuBsbn6VPcn33UH"

tests/custom-program/Cargo.toml

@@ -0,0 +1,8 @@
+[workspace]
+members = [
+    "programs/*"
+]
+resolver = "2"
+
+[profile.release]
+overflow-checks = true