lang: add custom error for owner

CHANGELOG.md

@@ -19,7 +19,7 @@ incremented for features.
 * lang: Add `mint::freeze_authority` keyword for mint initialization within `#[derive(Accounts)]` ([#835](https://github.com/project-serum/anchor/pull/835)).
 * lang: Add `AccountLoader` type for `zero_copy` accounts with support for CPI ([#792](https://github.com/project-serum/anchor/pull/792)).
 * lang: Add `#[account(init_if_needed)]` keyword for allowing one to invoke the same instruction even if the account was created already ([#906](https://github.com/project-serum/anchor/pull/906)).
-* lang: Add custom errors support for `signer`, `mut`, `has_one`, raw constraints and `address` ([#905](https://github.com/project-serum/anchor/pull/905), [#913](https://github.com/project-serum/anchor/pull/913)).
+* lang: Add custom errors support for `signer`, `mut`, `has_one`, `owner`, raw constraints and `address` ([#905](https://github.com/project-serum/anchor/pull/905), [#913](https://github.com/project-serum/anchor/pull/913)).
 
 ### Breaking
 

lang/derive/accounts/src/lib.rs

@@ -49,7 +49,7 @@ use syn::parse_macro_input;
 /// | `#[account(rent_exempt = <skip>)]` | On `AccountInfo` or `ProgramAccount` structs | Optional attribute to skip the rent exemption check. By default, all accounts marked with `#[account(init)]` will be rent exempt, and so this should rarely (if ever) be used. Similarly, omitting `= skip` will mark the account rent exempt. |
 /// | `#[account(executable)]` | On `AccountInfo` structs | Checks the given account is an executable program. |
 /// | `#[account(state = <target>)]` | On `CpiState` structs | Checks the given state is the canonical state account for the target program. |
-/// | `#[account(owner = <target>)]` | On `CpiState`, `CpiAccount`, and `AccountInfo` | Checks the account owner matches the target. |
+/// | `#[account(owner = <target>)]`<br><br>`#[account(owner = <target> @ <custom_error>)]` | On `CpiState`, `CpiAccount`, and `AccountInfo` | Checks the account owner matches the target. Custom errors are supported via `@`. |
 /// | `#[account(address = <pubkey>)]`<br><br>`#[account(address = <pubkey> @ <custom_error>)]` | On `AccountInfo` and `Account` | Checks the account key matches the pubkey. Custom errors are supported via `@`. |
 // TODO: How do we make the markdown render correctly without putting everything
 //       on absurdly long lines?

lang/syn/src/codegen/accounts/constraints.rs

@@ -250,9 +250,10 @@ pub fn generate_constraint_raw(c: &ConstraintRaw) -> proc_macro2::TokenStream {
 pub fn generate_constraint_owner(f: &Field, c: &ConstraintOwner) -> proc_macro2::TokenStream {
     let ident = &f.ident;
     let owner_address = &c.owner_address;
+    let error = generate_custom_error(&c.error, quote! { ConstraintOwner });
     quote! {
         if #ident.to_account_info().owner != &#owner_address {
-            return Err(anchor_lang::__private::ErrorCode::ConstraintOwner.into());
+            return Err(#error);
         }
     }
 }

lang/syn/src/lib.rs

@@ -634,6 +634,7 @@ pub struct ConstraintRaw {
 #[derive(Debug, Clone)]
 pub struct ConstraintOwner {
     pub owner_address: Expr,
+    pub error: Option<Expr>,
 }
 
 #[derive(Debug, Clone)]

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

@@ -200,6 +200,7 @@ pub fn parse_token(stream: ParseStream) -> ParseResult<ConstraintToken> {
                     span,
                     ConstraintOwner {
                         owner_address: stream.parse()?,
+                        error: parse_optional_custom_error(&stream)?,
                     },
                 )),
                 "rent_exempt" => ConstraintToken::RentExempt(Context::new(