Add error context and conversion methods to replace downcasting

Author: anorth

actors/init/src/lib.rs

@@ -4,11 +4,10 @@
 use cid::Cid;
 use fil_actors_runtime::runtime::builtins::Type;
 use fil_actors_runtime::runtime::{ActorCode, Runtime};
-use fil_actors_runtime::{actor_error, cbor, ActorDowncast, ActorError, SYSTEM_ACTOR_ADDR};
+use fil_actors_runtime::{actor_error, cbor, ActorContext, ActorError, SYSTEM_ACTOR_ADDR};
 use fvm_ipld_blockstore::Blockstore;
 use fvm_ipld_encoding::RawBytes;
 use fvm_shared::address::Address;
-use fvm_shared::error::ExitCode;
 use fvm_shared::{ActorID, MethodNum, METHOD_CONSTRUCTOR};
 use num_derive::FromPrimitive;
 use num_traits::FromPrimitive;
@@ -42,10 +41,7 @@ impl Actor {
     {
         let sys_ref: &Address = &SYSTEM_ACTOR_ADDR;
         rt.validate_immediate_caller_is(std::iter::once(sys_ref))?;
-        let state = State::new(rt.store(), params.network_name).map_err(|e| {
-            e.downcast_default(ExitCode::USR_ILLEGAL_STATE, "failed to construct init actor state")
-        })?;
-
+        let state = State::new(rt.store(), params.network_name)?;
         rt.create(&state)?;
 
         Ok(())
@@ -86,9 +82,8 @@ impl Actor {
         // Allocate an ID for this actor.
         // Store mapping of pubkey or actor address to actor ID
         let id_address: ActorID = rt.transaction(|s: &mut State, rt| {
-            s.map_address_to_new_id(rt.store(), &robust_address).map_err(|e| {
-                e.downcast_default(ExitCode::USR_ILLEGAL_STATE, "failed to allocate ID address")
-            })
+            s.map_address_to_new_id(rt.store(), &robust_address)
+                .context("failed to allocate ID address")
         })?;
 
         // Create an empty actor
@@ -101,7 +96,7 @@ impl Actor {
             params.constructor_params,
             rt.message().value_received(),
         )
-        .map_err(|err| err.wrap("constructor failed"))?;
+        .context("constructor failed")?;
 
         Ok(ExecReturn { id_address: Address::new_id(id_address), robust_address })
     }

actors/init/src/state.rs

@@ -3,7 +3,7 @@
 
 use cid::Cid;
 use fil_actors_runtime::{
-    actor_error, make_empty_map, make_map_with_root_and_bitwidth, AsActorError,
+    actor_error, make_empty_map, make_map_with_root_and_bitwidth, ActorError, AsActorError,
     FIRST_NON_SINGLETON_ADDR,
 };
 use fvm_ipld_blockstore::Blockstore;
@@ -22,7 +22,7 @@ pub struct State {
 }
 
 impl State {
-    pub fn new<BS: Blockstore>(store: &BS, network_name: String) -> anyhow::Result<Self> {
+    pub fn new<BS: Blockstore>(store: &BS, network_name: String) -> Result<Self, ActorError> {
         let empty_map = make_empty_map::<_, ()>(store, HAMT_BIT_WIDTH)
             .flush()
             .context_code(ExitCode::USR_ILLEGAL_STATE, "failed to create empty map")?;
@@ -37,22 +37,26 @@ impl State {
         &mut self,
         store: &BS,
         addr: &Address,
-    ) -> anyhow::Result<ActorID> {
+    ) -> Result<ActorID, ActorError> {
         let id = self.next_id;
         self.next_id += 1;
 
-        let mut map = make_map_with_root_and_bitwidth(&self.address_map, store, HAMT_BIT_WIDTH)?;
-        let is_new = map.set_if_absent(addr.to_bytes().into(), id)?;
+        let mut map = make_map_with_root_and_bitwidth(&self.address_map, store, HAMT_BIT_WIDTH)
+            .context_code(ExitCode::USR_ILLEGAL_STATE, "failed to load address map")?;
+        let is_new = map
+            .set_if_absent(addr.to_bytes().into(), id)
+            .context_code(ExitCode::USR_ILLEGAL_STATE, "failed to set map key")?;
         if !is_new {
             // this is impossible today as the robust address is a hash of unique inputs
             // but in close future predictable address generation will make this possible
-            return Err(anyhow!(actor_error!(
+            return Err(actor_error!(
                 forbidden,
                 "robust address {} is already allocated in the address map",
                 addr
-            )));
+            ));
         }
-        self.address_map = map.flush()?;
+        self.address_map =
+            map.flush().context_code(ExitCode::USR_ILLEGAL_STATE, "failed to store address map")?;
 
         Ok(id)
     }
@@ -71,14 +75,18 @@ impl State {
         &self,
         store: &BS,
         addr: &Address,
-    ) -> anyhow::Result<Option<Address>> {
+    ) -> Result<Option<Address>, ActorError> {
         if addr.protocol() == Protocol::ID {
             return Ok(Some(*addr));
         }
 
-        let map = make_map_with_root_and_bitwidth(&self.address_map, store, HAMT_BIT_WIDTH)?;
+        let map = make_map_with_root_and_bitwidth(&self.address_map, store, HAMT_BIT_WIDTH)
+            .context_code(ExitCode::USR_ILLEGAL_STATE, "failed to load address map")?;
 
-        Ok(map.get(&addr.to_bytes())?.copied().map(Address::new_id))
+        let found = map
+            .get(&addr.to_bytes())
+            .context_code(ExitCode::USR_ILLEGAL_STATE, "failed to get address entry")?;
+        Ok(found.copied().map(Address::new_id))
     }
 }