Drozdziak1/p2w init rent adjustment (#269)

* pyth2wormhole: add rent adjustment to the initialize() instruction

* pyth2wormhole migrate(): Leave a note about rent adjustment

The migrate() ix won't be called in the nearest future - it does not
make sense to bloat the program bytecode with the rent adjustment. The
note describes the what and why in detail.

Author: Stanisław Drozd

solana/pyth2wormhole/program/src/initialize.rs

@@ -1,4 +1,10 @@
-use solana_program::pubkey::Pubkey;
+use solana_program::{
+    program::invoke,
+    pubkey::Pubkey,
+    rent::Rent,
+    system_instruction,
+    sysvar::Sysvar,
+};
 use solitaire::{
     trace,
     AccountState,
@@ -35,5 +41,21 @@ pub fn initialize(
         .create(ctx, accs.payer.info().key, CreationLamports::Exempt)?;
     accs.new_config.1 = data;
 
+    // TODO(2022-09-05): Remove this rent collection after
+    // sysvar-based rent calculation becomes mainline in Solitaire.
+    let config_balance = accs.new_config.info().lamports();
+    let config_rent_exempt = Rent::get()?.minimum_balance(accs.new_config.info().data_len());
+
+    if config_balance < config_rent_exempt {
+        let required_deposit = config_rent_exempt - config_balance;
+
+        let transfer_ix = system_instruction::transfer(
+            accs.payer.key,
+            accs.new_config.info().key,
+            required_deposit,
+        );
+        invoke(&transfer_ix, ctx.accounts)?
+    }
+
     Ok(())
 }

solana/pyth2wormhole/program/src/migrate.rs

@@ -70,6 +70,13 @@ pub fn migrate(ctx: &ExecutionContext, accs: &mut Migrate, data: ()) -> SoliResu
         ));
     }
 
+    // NOTE(2022-09-06): This instruction does not contain the temporary rent
+    // adjustment snippet necessary for PythNet compatibility. This
+    // was done to minimize the footprint of this rather hacky
+    // workaround. In case the migrate ix needs to be ran in a
+    // weird-rent environment, copy the rent due snippet and adjust it
+    // to work against `accs.new_config`.
+
     // Populate new config
     accs.new_config
         .create(ctx, accs.payer.info().key, CreationLamports::Exempt)?;