lang: Don't make anchor_lang implicitly mandatory as an extra dependency when using declare_program! via anchor_client (solana-foundation#4157)

Author: cryptopapi997

CHANGELOG.md

@@ -16,6 +16,7 @@ The minor version will be incremented upon a breaking change and the patch versi
 - cli: Added a `check_program_id_mismatch` in build time to check if the program ID in the source code matches the program ID in the keypair file ([#4018](https://github.com/solana-foundation/anchor/pull/4018)). This check will be skipped during `anchor test`.
 - lang: Add instruction parser to `declare_program!` ([#4118](https://github.com/solana-foundation/anchor/pull/4118)).
 - ts: Export all IDL types from the root. Users can now update `dist/cjs/idl` imports to import directly from `@anchor-lang/core` ([#3948](https://github.com/solana-foundation/anchor/pull/3948)).
+- lang: Add `declare_program!` support with just `anchor_client` and not `anchor_lang` ([#4157](https://github.com/solana-foundation/anchor/pull/4157)).
 
 ### Fixes
 

lang/attribute/program/src/declare_program/mod.rs

@@ -74,6 +74,11 @@ fn gen_program(idl: &Idl, name: &syn::Ident) -> proc_macro2::TokenStream {
     quote! {
         #docs
         pub mod #name {
+            #[cfg(any(target_os = "solana", feature = "idl-build"))]
+            use ::anchor_lang;
+            #[cfg(all(not(target_os = "solana"), not(feature = "idl-build")))]
+            use super::anchor_lang;
+
             use anchor_lang::prelude::*;
             use accounts::*;
             use events::*;

lang/attribute/program/src/declare_program/mods/errors.rs

@@ -15,6 +15,7 @@ pub fn gen_errors_mod(idl: &Idl) -> proc_macro2::TokenStream {
             /// Program error type definitions.
             #[cfg(not(feature = "idl-build"))]
             pub mod errors {
+                use super::*;
             }
         };
     }
@@ -23,6 +24,7 @@ pub fn gen_errors_mod(idl: &Idl) -> proc_macro2::TokenStream {
         /// Program error type definitions.
         #[cfg(not(feature = "idl-build"))]
         pub mod errors {
+            use super::*;
 
             #[anchor_lang::error_code(offset = 0)]
             pub enum ProgramError {

lang/attribute/program/src/lib.rs

@@ -58,6 +58,15 @@ pub fn program(
 /// definition, you should consider creating a separate crate for the external program definition
 /// and reusing it in your programs.
 ///
+/// # Off-chain usage
+///
+/// When using in off-chain environments, for example via `anchor_client`, you must have
+/// `anchor_lang` in scope:
+///
+/// ```ignore
+/// use anchor_client::anchor_lang;
+/// ```
+///
 /// # Example
 ///
 /// A full on-chain CPI usage example can be found [here].

lang/src/lib.rs

@@ -498,6 +498,8 @@ pub mod prelude {
         InitSpace, Key, Lamports, Owner, ProgramData, Result, Space, ToAccountInfo, ToAccountInfos,
         ToAccountMetas,
     };
+    // Re-export the crate as anchor_lang for declare_program! macro
+    pub use crate as anchor_lang;
     pub use crate::solana_program::account_info::{next_account_info, AccountInfo};
     pub use crate::solana_program::instruction::AccountMeta;
     pub use crate::solana_program::program_error::ProgramError;