lang: Add Accounts trait for Vec (#417)

lang/src/vec.rs

@@ -1,6 +1,8 @@
-use crate::{ToAccountInfos, ToAccountMetas};
+use crate::{Accounts, ToAccountInfos, ToAccountMetas};
 use solana_program::account_info::AccountInfo;
 use solana_program::instruction::AccountMeta;
+use solana_program::program_error::ProgramError;
+use solana_program::pubkey::Pubkey;
 
 impl<'info, T: ToAccountInfos<'info>> ToAccountInfos<'info> for Vec<T> {
     fn to_account_infos(&self) -> Vec<AccountInfo<'info>> {
@@ -17,3 +19,77 @@ impl<T: ToAccountMetas> ToAccountMetas for Vec<T> {
             .collect()
     }
 }
+
+impl<'info, T: Accounts<'info>> Accounts<'info> for Vec<T> {
+    fn try_accounts(
+        program_id: &Pubkey,
+        accounts: &mut &[AccountInfo<'info>],
+        ix_data: &[u8],
+    ) -> Result<Self, ProgramError> {
+        let mut vec: Vec<T> = Vec::new();
+        T::try_accounts(program_id, accounts, ix_data).map(|item| vec.push(item))?;
+        Ok(vec)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::ToAccountInfo;
+    use solana_program::clock::Epoch;
+    use solana_program::pubkey::Pubkey;
+
+    use super::*;
+
+    #[derive(Accounts)]
+    pub struct Test<'info> {
+        #[account(signer)]
+        test: AccountInfo<'info>,
+    }
+
+    #[test]
+    fn test_accounts_trait_for_vec() {
+        let program_id = Pubkey::default();
+
+        let key = Pubkey::default();
+        let mut lamports1 = 0;
+        let mut data1 = vec![0; 10];
+        let owner = Pubkey::default();
+        let account1 = AccountInfo::new(
+            &key,
+            true,
+            true,
+            &mut lamports1,
+            &mut data1,
+            &owner,
+            false,
+            Epoch::default(),
+        );
+
+        let mut lamports2 = 0;
+        let mut data2 = vec![0; 10];
+        let account2 = AccountInfo::new(
+            &key,
+            true,
+            true,
+            &mut lamports2,
+            &mut data2,
+            &owner,
+            false,
+            Epoch::default(),
+        );
+
+        let mut accounts = &[account1, account2][..];
+        let parsed_accounts = Vec::<Test>::try_accounts(&program_id, &mut accounts, &[]).unwrap();
+
+        assert_eq!(accounts.len(), parsed_accounts.len());
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_accounts_trait_for_vec_empty() {
+        let program_id = Pubkey::default();
+
+        let mut accounts = &[][..];
+        Vec::<Test>::try_accounts(&program_id, &mut accounts, &[]).unwrap();
+    }
+}