refactor(finance/escrow): extract PDA-aware token transfer/close helpers

Add an owning_pda_seeds option to transfer_tokens and a new
close_token_account helper in shared.rs, then use them across
make_offer, take_offer, and cancel_offer. This removes the duplicated
CpiContext::new_with_signer + transfer_checked/close_account boilerplate
that was hand-rolled in each handler.

No behavior change: per-maker PDA seeds and has_one checks are unchanged.
Verified with cargo test (5 tests pass).

Author: mikemaccana

finance/escrow/anchor/programs/escrow/src/instructions/cancel_offer.rs

@@ -2,14 +2,13 @@ use anchor_lang::prelude::*;
 
 use anchor_spl::{
     associated_token::AssociatedToken,
-    token_interface::{
-        close_account, transfer_checked, CloseAccount, Mint, TokenAccount, TokenInterface,
-        TransferChecked,
-    },
+    token_interface::{Mint, TokenAccount, TokenInterface},
 };
 
 use crate::Offer;
 
+use super::{close_token_account, transfer_tokens};
+
 // Cancel an outstanding offer. Without this handler, an abandoned offer would
 // keep the maker's token-A locked in the vault forever (and the offer
 // account's rent unclaimed). The maker signs, the vault tokens flow back to
@@ -55,45 +54,28 @@ pub struct CancelOffer<'info> {
 pub fn handle_cancel_offer(context: Context<CancelOffer>) -> Result<()> {
     let maker_key = context.accounts.maker.key();
     let id_bytes = context.accounts.offer.id.to_le_bytes();
-    let seeds = &[
-        b"offer".as_ref(),
-        maker_key.as_ref(),
-        id_bytes.as_ref(),
-        &[context.accounts.offer.bump],
-    ];
-    let signer_seeds = [&seeds[..]];
+    let bump = [context.accounts.offer.bump];
+    let offer_seeds: &[&[u8]] = &[b"offer", maker_key.as_ref(), id_bytes.as_ref(), &bump];
 
     // Move all tokens back from the vault to the maker.
-    let vault_amount = context.accounts.vault.amount;
-    let transfer_accounts = TransferChecked {
-        from: context.accounts.vault.to_account_info(),
-        mint: context.accounts.token_mint_a.to_account_info(),
-        to: context.accounts.maker_token_account_a.to_account_info(),
-        authority: context.accounts.offer.to_account_info(),
-    };
-    let cpi_context = CpiContext::new_with_signer(
-        context.accounts.token_program.key(),
-        transfer_accounts,
-        &signer_seeds,
-    );
-    transfer_checked(
-        cpi_context,
-        vault_amount,
-        context.accounts.token_mint_a.decimals,
+    transfer_tokens(
+        &context.accounts.vault,
+        &context.accounts.maker_token_account_a,
+        &context.accounts.vault.amount,
+        &context.accounts.token_mint_a,
+        &context.accounts.offer.to_account_info(),
+        &context.accounts.token_program,
+        Some(offer_seeds),
     )?;
 
     // Close the vault, sending its rent lamports back to the maker.
-    let close_accounts = CloseAccount {
-        account: context.accounts.vault.to_account_info(),
-        destination: context.accounts.maker.to_account_info(),
-        authority: context.accounts.offer.to_account_info(),
-    };
-    let cpi_context = CpiContext::new_with_signer(
-        context.accounts.token_program.key(),
-        close_accounts,
-        &signer_seeds,
-    );
-    close_account(cpi_context)?;
+    close_token_account(
+        &context.accounts.vault,
+        &context.accounts.maker.to_account_info(),
+        &context.accounts.offer.to_account_info(),
+        &context.accounts.token_program,
+        Some(offer_seeds),
+    )?;
 
     // The offer account itself is closed by the `close = maker` constraint
     // above, which refunds its rent to the maker.

finance/escrow/anchor/programs/escrow/src/instructions/make_offer.rs

@@ -76,8 +76,9 @@ pub fn handle_send_offered_tokens_to_vault(
         &context.accounts.vault,
         &token_a_offered_amount,
         &context.accounts.token_mint_a,
-        &context.accounts.maker,
+        &context.accounts.maker.to_account_info(),
         &context.accounts.token_program,
+        None,
     )
 }
 

finance/escrow/anchor/programs/escrow/src/instructions/shared.rs

@@ -1,16 +1,21 @@
 use anchor_lang::prelude::*;
 
 use anchor_spl::token_interface::{
-    transfer_checked, Mint, TokenAccount, TokenInterface, TransferChecked,
+    close_account, transfer_checked, CloseAccount, Mint, TokenAccount, TokenInterface,
+    TransferChecked,
 };
 
+// Transfer tokens from one token account to another.
+// When transferring out of a token account owned by a PDA, pass the PDA's
+// signer seeds via owning_pda_seeds; otherwise pass None.
 pub fn transfer_tokens<'info>(
     from: &InterfaceAccount<'info, TokenAccount>,
     to: &InterfaceAccount<'info, TokenAccount>,
     amount: &u64,
     mint: &InterfaceAccount<'info, Mint>,
-    authority: &Signer<'info>,
+    authority: &AccountInfo<'info>,
     token_program: &Interface<'info, TokenInterface>,
+    owning_pda_seeds: Option<&[&[u8]]>,
 ) -> Result<()> {
     let transfer_accounts = TransferChecked {
         from: from.to_account_info(),
@@ -19,7 +24,40 @@ pub fn transfer_tokens<'info>(
         authority: authority.to_account_info(),
     };
 
-    let cpi_context = CpiContext::new(token_program.key(), transfer_accounts);
+    let signer_seeds = owning_pda_seeds.map(|seeds| [seeds]);
+    let cpi_context = match signer_seeds.as_ref() {
+        Some(signer_seeds) => {
+            CpiContext::new_with_signer(token_program.key(), transfer_accounts, signer_seeds)
+        }
+        None => CpiContext::new(token_program.key(), transfer_accounts),
+    };
 
     transfer_checked(cpi_context, *amount, mint.decimals)
 }
+
+// Close a token account, sending its rent lamports to destination.
+// When the token account is owned by a PDA, pass the PDA's signer seeds via
+// owning_pda_seeds; otherwise pass None.
+pub fn close_token_account<'info>(
+    token_account: &InterfaceAccount<'info, TokenAccount>,
+    destination: &AccountInfo<'info>,
+    authority: &AccountInfo<'info>,
+    token_program: &Interface<'info, TokenInterface>,
+    owning_pda_seeds: Option<&[&[u8]]>,
+) -> Result<()> {
+    let close_accounts = CloseAccount {
+        account: token_account.to_account_info(),
+        destination: destination.to_account_info(),
+        authority: authority.to_account_info(),
+    };
+
+    let signer_seeds = owning_pda_seeds.map(|seeds| [seeds]);
+    let cpi_context = match signer_seeds.as_ref() {
+        Some(signer_seeds) => {
+            CpiContext::new_with_signer(token_program.key(), close_accounts, signer_seeds)
+        }
+        None => CpiContext::new(token_program.key(), close_accounts),
+    };
+
+    close_account(cpi_context)
+}

finance/escrow/anchor/programs/escrow/src/instructions/take_offer.rs

@@ -2,15 +2,12 @@ use anchor_lang::prelude::*;
 
 use anchor_spl::{
     associated_token::AssociatedToken,
-    token_interface::{
-        close_account, transfer_checked, CloseAccount, Mint, TokenAccount, TokenInterface,
-        TransferChecked,
-    },
+    token_interface::{Mint, TokenAccount, TokenInterface},
 };
 
 use crate::Offer;
 
-use super::transfer_tokens;
+use super::{close_token_account, transfer_tokens};
 
 #[derive(Accounts)]
 pub struct TakeOffer<'info> {
@@ -82,50 +79,33 @@ pub fn handle_send_wanted_tokens_to_maker(context: &Context<TakeOffer>) -> Resul
         &context.accounts.maker_token_account_b,
         &context.accounts.offer.token_b_wanted_amount,
         &context.accounts.token_mint_b,
-        &context.accounts.taker,
+        &context.accounts.taker.to_account_info(),
         &context.accounts.token_program,
+        None,
     )
 }
 
 pub fn handle_withdraw_and_close_vault(context: Context<TakeOffer>) -> Result<()> {
-    let seeds = &[
-        b"offer",
-        context.accounts.maker.to_account_info().key.as_ref(),
-        &context.accounts.offer.id.to_le_bytes()[..],
-        &[context.accounts.offer.bump],
-    ];
-    let signer_seeds = [&seeds[..]];
-
-    let accounts = TransferChecked {
-        from: context.accounts.vault.to_account_info(),
-        mint: context.accounts.token_mint_a.to_account_info(),
-        to: context.accounts.taker_token_account_a.to_account_info(),
-        authority: context.accounts.offer.to_account_info(),
-    };
-
-    let cpi_context = CpiContext::new_with_signer(
-        context.accounts.token_program.key(),
-        accounts,
-        &signer_seeds,
-    );
-
-    transfer_checked(
-        cpi_context,
-        context.accounts.vault.amount,
-        context.accounts.token_mint_a.decimals,
-    )?;
-
-    let accounts = CloseAccount {
-        account: context.accounts.vault.to_account_info(),
-        destination: context.accounts.taker.to_account_info(),
-        authority: context.accounts.offer.to_account_info(),
-    };
+    let maker_key = context.accounts.maker.key();
+    let id_bytes = context.accounts.offer.id.to_le_bytes();
+    let bump = [context.accounts.offer.bump];
+    let offer_seeds: &[&[u8]] = &[b"offer", maker_key.as_ref(), id_bytes.as_ref(), &bump];
 
-    let cpi_context = CpiContext::new_with_signer(
-        context.accounts.token_program.key(),
-        accounts,
-        &signer_seeds,
-    );
+    transfer_tokens(
+        &context.accounts.vault,
+        &context.accounts.taker_token_account_a,
+        &context.accounts.vault.amount,
+        &context.accounts.token_mint_a,
+        &context.accounts.offer.to_account_info(),
+        &context.accounts.token_program,
+        Some(offer_seeds),
+    )?;
 
-    close_account(cpi_context)
+    close_token_account(
+        &context.accounts.vault,
+        &context.accounts.taker.to_account_info(),
+        &context.accounts.offer.to_account_info(),
+        &context.accounts.token_program,
+        Some(offer_seeds),
+    )
 }