From 00a86272b8127c14fdddb570c2e97253eb508de7 Mon Sep 17 00:00:00 2001
From: Andreas Fackler <andreas.fackler@linera.io>
Date: Thu, 15 Aug 2024 14:43:56 +0200
Subject: [PATCH] ChainStateView::execute_block can now activate a chain.

---
 linera-chain/src/chain.rs                     | 59 +++++++++++++------
 linera-chain/src/data_types.rs                | 13 +---
 .../chain_worker/state/temporary_changes.rs   |  2 -
 3 files changed, 43 insertions(+), 31 deletions(-)

diff --git a/linera-chain/src/chain.rs b/linera-chain/src/chain.rs
index 8122db41bc2..6fb695c043c 100644
--- a/linera-chain/src/chain.rs
+++ b/linera-chain/src/chain.rs
@@ -678,7 +678,7 @@ where
     }
 
     /// Executes a block: first the incoming messages, then the main operation.
-    /// * Modifies the state of inboxes, outboxes, and channels, if needed.
+    /// * Modifies the state of outboxes and channels, if needed.
     /// * As usual, in case of errors, `self` may not be consistent any more and should be thrown
     ///   away.
     /// * Returns the list of messages caused by the block being executed.
@@ -693,6 +693,47 @@ where
 
         let chain_id = self.chain_id();
         assert_eq!(block.chain_id, chain_id);
+        // The first incoming message of any child chain must be `OpenChain`. A root chain must
+        // already be initialized
+        if block.height == BlockHeight::ZERO
+            && self
+                .execution_state
+                .system
+                .description
+                .get()
+                .map_or(true, |description| description.is_child())
+        {
+            let Some(in_bundle) = block
+                .incoming_bundles
+                .first()
+                .filter(|in_bundle| in_bundle.action == MessageAction::Accept)
+            else {
+                return Err(ChainError::InactiveChain(chain_id));
+            };
+            let Some(posted_message) =
+                in_bundle.bundle.messages.first().filter(|pm| {
+                    matches!(pm.message, Message::System(SystemMessage::OpenChain(_)))
+                })
+            else {
+                return Err(ChainError::InactiveChain(chain_id));
+            };
+
+            if !self.is_active() {
+                let message_id = MessageId {
+                    chain_id: in_bundle.origin.sender,
+                    height: in_bundle.bundle.height,
+                    index: posted_message.index,
+                };
+                self.execute_init_message(
+                    message_id,
+                    &posted_message.message,
+                    block.timestamp,
+                    local_time,
+                )
+                .await?;
+            }
+        }
+
         ensure!(
             *self.execution_state.system.timestamp.get() <= block.timestamp,
             ChainError::InvalidBlockTimestamp
@@ -713,22 +754,6 @@ where
                 ChainError::ClosedChain
             );
         }
-
-        // The first incoming message of any child chain must be `OpenChain`. A root chain must
-        // already be initialized
-        if block.height == BlockHeight::ZERO
-            && self
-                .execution_state
-                .system
-                .description
-                .get()
-                .map_or(true, |description| description.is_child())
-        {
-            ensure!(
-                block.starts_with_open_chain(),
-                ChainError::InactiveChain(self.chain_id())
-            );
-        }
         let app_permissions = self.execution_state.system.application_permissions.get();
         let mut mandatory = HashSet::<UserApplicationId>::from_iter(
             app_permissions.mandatory_applications.iter().cloned(),
diff --git a/linera-chain/src/data_types.rs b/linera-chain/src/data_types.rs
index c5c941aca6d..bfc3a5cefb7 100644
--- a/linera-chain/src/data_types.rs
+++ b/linera-chain/src/data_types.rs
@@ -16,7 +16,7 @@ use linera_base::{
 };
 use linera_execution::{
     committee::{Committee, Epoch, ValidatorName},
-    BytecodeLocation, Message, MessageKind, Operation, SystemMessage, SystemOperation,
+    BytecodeLocation, Message, MessageKind, Operation, SystemOperation,
 };
 use serde::{de::Deserializer, Deserialize, Serialize};
 
@@ -96,17 +96,6 @@ impl Block {
                 .all(|message| message.action == MessageAction::Reject)
     }
 
-    /// Returns whether `OpenChain` is the first message in this block.
-    pub fn starts_with_open_chain(&self) -> bool {
-        let Some(posted_message) = self.incoming_messages().next() else {
-            return false;
-        };
-        matches!(
-            posted_message.message,
-            Message::System(SystemMessage::OpenChain(_))
-        )
-    }
-
     /// Returns an iterator over all incoming [`PostedMessage`]s in this block.
     pub fn incoming_messages(&self) -> impl Iterator<Item = &PostedMessage> {
         self.incoming_bundles
diff --git a/linera-core/src/chain_worker/state/temporary_changes.rs b/linera-core/src/chain_worker/state/temporary_changes.rs
index 7c920983548..f34a4aee544 100644
--- a/linera-core/src/chain_worker/state/temporary_changes.rs
+++ b/linera-core/src/chain_worker/state/temporary_changes.rs
@@ -139,8 +139,6 @@ where
         &mut self,
         block: Block,
     ) -> Result<(ExecutedBlock, ChainInfoResponse), WorkerError> {
-        self.0.ensure_is_active()?;
-
         let local_time = self.0.storage.clock().current_time();
         let signer = block.authenticated_signer;