Add test to enforce that program id account info for CPI is optional (#22069)

* Update tests to demonstrate that program id account info for CPI is optional

* Clean up comments that say that program id account info is required

programs/bpf/rust/instruction_introspection/src/lib.rs

@@ -54,7 +54,7 @@ fn process_instruction(
                 &[instruction_data[0], instruction_data[1], 1],
                 vec![AccountMeta::new_readonly(instructions::id(), false)],
             ),
-            accounts,
+            &[instructions_account.clone()],
         )?;
     }
 

programs/bpf/rust/invoke_and_return/src/lib.rs

@@ -14,7 +14,6 @@ fn process_instruction(
     instruction_data: &[u8],
 ) -> ProgramResult {
     let to_call = accounts[0].key;
-    let infos = accounts;
     let instruction = Instruction {
         accounts: accounts[1..]
             .iter()
@@ -27,5 +26,7 @@ fn process_instruction(
         data: instruction_data.to_owned(),
         program_id: *to_call,
     };
-    invoke(&instruction, infos)
+    // program id account is not required for invocations if the
+    // program id is not one of the instruction account metas.
+    invoke(&instruction, &accounts[1..])
 }

programs/bpf/rust/upgradeable/src/lib.rs

@@ -8,13 +8,12 @@ use solana_program::{
 
 entrypoint!(process_instruction);
 fn process_instruction(
-    program_id: &Pubkey,
+    _program_id: &Pubkey,
     accounts: &[AccountInfo],
     _instruction_data: &[u8],
 ) -> ProgramResult {
     msg!("Upgradeable program");
-    assert_eq!(accounts.len(), 2);
-    assert_eq!(accounts[0].key, program_id);
-    assert_eq!(*accounts[1].key, clock::id());
+    assert_eq!(accounts.len(), 1);
+    assert_eq!(*accounts[0].key, clock::id());
     Err(42.into())
 }

programs/bpf/rust/upgraded/src/lib.rs

@@ -8,13 +8,12 @@ use solana_program::{
 
 entrypoint!(process_instruction);
 fn process_instruction(
-    program_id: &Pubkey,
+    _program_id: &Pubkey,
     accounts: &[AccountInfo],
     _instruction_data: &[u8],
 ) -> ProgramResult {
     msg!("Upgraded program");
-    assert_eq!(accounts.len(), 2);
-    assert_eq!(accounts[0].key, program_id);
-    assert_eq!(*accounts[1].key, clock::id());
+    assert_eq!(accounts.len(), 1);
+    assert_eq!(*accounts[0].key, clock::id());
     Err(43.into())
 }