feature gate: init program with RevokePendingActivation instruction (#5510)

* feature gate: init program

* move to program folder

* address latest feedback

Author: Joe C

Cargo.lock

@@ -13,6 +13,7 @@ members = [
   "examples/rust/sysvar",
   "examples/rust/transfer-lamports",
   "examples/rust/transfer-tokens",
+  "feature-gate/program",
   "feature-proposal/program",
   "feature-proposal/cli",
   "governance/addin-mock/program",

Cargo.toml

@@ -0,0 +1,9 @@
+# Feature Gate Program
+
+This program serves to manage new features on Solana.
+
+It serves one purpose: revoking features that are pending activation.
+
+More information & documentation will follow as this program matures, but you
+can follow the discussions
+[here](https://github.com/solana-labs/solana/issues/32780)!

feature-gate/README.md

@@ -0,0 +1,27 @@
+[package]
+name = "spl-feature-gate"
+version = "0.1.0"
+description = "Solana Program Library Feature Gate Program"
+authors = ["Solana Labs Maintainers <[email protected]>"]
+repository = "https://github.com/solana-labs/solana-program-library"
+license = "Apache-2.0"
+edition = "2021"
+
+[features]
+no-entrypoint = []
+test-sbf = []
+
+[dependencies]
+num_enum = "0.7.0"
+solana-program = "1.16.16"
+spl-program-error = { version = "0.3.0", path = "../../libraries/program-error" }
+
+[dev-dependencies]
+solana-program-test = "1.16.16"
+solana-sdk = "1.16.16"
+
+[lib]
+crate-type = ["cdylib", "lib"]
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]

feature-gate/program/Cargo.toml

@@ -0,0 +1,17 @@
+//! Program entrypoint
+
+use {
+    crate::processor,
+    solana_program::{
+        account_info::AccountInfo, entrypoint, entrypoint::ProgramResult, pubkey::Pubkey,
+    },
+};
+
+entrypoint!(process_instruction);
+fn process_instruction(
+    program_id: &Pubkey,
+    accounts: &[AccountInfo],
+    input: &[u8],
+) -> ProgramResult {
+    processor::process(program_id, accounts, input)
+}

feature-gate/program/src/entrypoint.rs

@@ -0,0 +1,14 @@
+//! Program error types
+
+use spl_program_error::*;
+
+/// Program specific errors
+#[spl_program_error]
+pub enum FeatureGateError {
+    /// Operation overflowed
+    #[error("Operation overflowed")]
+    Overflow,
+    /// Feature already activated
+    #[error("Feature already activated")]
+    FeatureAlreadyActivated,
+}

feature-gate/program/src/error.rs

@@ -0,0 +1,77 @@
+//! Program instructions
+
+use {
+    num_enum::{IntoPrimitive, TryFromPrimitive},
+    solana_program::{
+        instruction::{AccountMeta, Instruction},
+        program_error::ProgramError,
+        pubkey::Pubkey,
+    },
+};
+
+/// Feature Gate program instructions
+#[derive(Clone, Debug, PartialEq, IntoPrimitive, TryFromPrimitive)]
+#[repr(u8)]
+pub enum FeatureGateInstruction {
+    /// Revoke a pending feature activation.
+    ///
+    /// A "pending" feature activation is a feature account that has been
+    /// allocated and assigned, but hasn't yet been updated by the runtime
+    /// with an `activation_slot`.
+    ///
+    /// Features that _have_ been activated by the runtime cannot be revoked.
+    ///
+    /// Accounts expected by this instruction:
+    ///
+    ///   0. `[w+s]`    Feature account
+    ///   1. `[w]`      Destination (for rent lamports)
+    RevokePendingActivation,
+}
+impl FeatureGateInstruction {
+    /// Unpacks a byte buffer into a
+    /// [FeatureGateInstruction](enum.FeatureGateInstruction.html).
+    pub fn unpack(input: &[u8]) -> Result<Self, ProgramError> {
+        if input.len() != 1 {
+            return Err(ProgramError::InvalidInstructionData);
+        }
+        Self::try_from(input[0]).map_err(|_| ProgramError::InvalidInstructionData)
+    }
+
+    /// Packs a [FeatureGateInstruction](enum.FeatureGateInstruction.html) into
+    /// a byte buffer.
+    pub fn pack(&self) -> Vec<u8> {
+        vec![self.to_owned().into()]
+    }
+}
+
+/// Creates a 'RevokePendingActivation' instruction.
+pub fn revoke_pending_activation(feature_id: &Pubkey, destination: &Pubkey) -> Instruction {
+    let accounts = vec![
+        AccountMeta::new(*feature_id, true),
+        AccountMeta::new(*destination, false),
+    ];
+
+    let data = FeatureGateInstruction::RevokePendingActivation.pack();
+
+    Instruction {
+        program_id: crate::id(),
+        accounts,
+        data,
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    fn test_pack_unpack(instruction: &FeatureGateInstruction) {
+        let packed = instruction.pack();
+        let unpacked = FeatureGateInstruction::unpack(&packed).unwrap();
+        assert_eq!(instruction, &unpacked);
+    }
+
+    #[test]
+    fn test_pack_unpack_revoke_pending_activation() {
+        test_pack_unpack(&FeatureGateInstruction::RevokePendingActivation);
+    }
+}

feature-gate/program/src/instruction.rs

@@ -0,0 +1,16 @@
+//! Feature Gate program
+
+#![deny(missing_docs)]
+#![cfg_attr(not(test), forbid(unsafe_code))]
+
+#[cfg(not(feature = "no-entrypoint"))]
+mod entrypoint;
+pub mod error;
+pub mod instruction;
+pub mod processor;
+
+// Export current SDK types for downstream users building with a different SDK
+// version
+pub use solana_program;
+
+solana_program::declare_id!("Feature111111111111111111111111111111111111");

feature-gate/program/src/lib.rs

@@ -0,0 +1,62 @@
+//! Program state processor
+
+use {
+    crate::{error::FeatureGateError, instruction::FeatureGateInstruction},
+    solana_program::{
+        account_info::{next_account_info, AccountInfo},
+        entrypoint::ProgramResult,
+        feature::Feature,
+        msg,
+        program_error::ProgramError,
+        pubkey::Pubkey,
+        system_program,
+    },
+};
+
+/// Processes a [RevokePendingActivation](enum.FeatureGateInstruction.html)
+/// instruction.
+pub fn process_revoke_pending_activation(
+    _program_id: &Pubkey,
+    accounts: &[AccountInfo],
+) -> ProgramResult {
+    let account_info_iter = &mut accounts.iter();
+
+    let feature_info = next_account_info(account_info_iter)?;
+    let destination_info = next_account_info(account_info_iter)?;
+
+    if !feature_info.is_signer {
+        return Err(ProgramError::MissingRequiredSignature);
+    }
+
+    // This will also check the program ID
+    if Feature::from_account_info(feature_info)?
+        .activated_at
+        .is_some()
+    {
+        return Err(FeatureGateError::FeatureAlreadyActivated.into());
+    }
+
+    let new_destination_lamports = feature_info
+        .lamports()
+        .checked_add(destination_info.lamports())
+        .ok_or::<ProgramError>(FeatureGateError::Overflow.into())?;
+
+    **feature_info.try_borrow_mut_lamports()? = 0;
+    **destination_info.try_borrow_mut_lamports()? = new_destination_lamports;
+
+    feature_info.realloc(0, true)?;
+    feature_info.assign(&system_program::id());
+
+    Ok(())
+}
+
+/// Processes an [Instruction](enum.Instruction.html).
+pub fn process(program_id: &Pubkey, accounts: &[AccountInfo], input: &[u8]) -> ProgramResult {
+    let instruction = FeatureGateInstruction::unpack(input)?;
+    match instruction {
+        FeatureGateInstruction::RevokePendingActivation => {
+            msg!("Instruction: RevokePendingActivation");
+            process_revoke_pending_activation(program_id, accounts)
+        }
+    }
+}