linera-views: centralize the ViewError: From<Context::Error> bound into Context (#4029)

## Motivation

We consistently require that the store errors be convertible to
`ViewError`, but we don't encode that bound in `Context`, so we
duplicate `ViewError: From<Context::Error>` bounds throughout the
codebase.

## Proposal

Move the bound into the definition of the `Context` trait instead.

While we're at it, use a boxed error for the store errors in `ViewError`
instead of converting to string, so that the backtrace and other error
metadata isn't lost.

## Test Plan

CI.

## Release Plan

- Nothing to do / These changes follow the usual release cycle.

## Links

- [reviewer
checklist](https://github.com/linera-io/linera-protocol/blob/main/CONTRIBUTING.md#reviewer-checklist)

Author: Twey

Cargo.lock

@@ -13,7 +13,8 @@ use linera_views::{
     context::Context,
     queue_view::QueueView,
     register_view::RegisterView,
-    views::{ClonableView, View, ViewError},
+    views::{ClonableView, View},
+    ViewError,
 };
 use serde::{Deserialize, Serialize};
 use thiserror::Error;

linera-chain/src/inbox.rs

@@ -31,7 +31,7 @@ use linera_base::{
     identifiers::{ApplicationId, ChainId},
 };
 use linera_execution::ExecutionError;
-use linera_views::views::ViewError;
+use linera_views::ViewError;
 use rand_distr::WeightedError;
 use thiserror::Error;
 

linera-chain/src/lib.rs

@@ -84,7 +84,8 @@ use linera_views::{
     context::Context,
     map_view::MapView,
     register_view::RegisterView,
-    views::{ClonableView, View, ViewError},
+    views::{ClonableView, View},
+    ViewError,
 };
 use rand_chacha::{rand_core::SeedableRng, ChaCha8Rng};
 use rand_distr::{Distribution, WeightedAliasIndex};

linera-chain/src/manager.rs

@@ -8,7 +8,8 @@ use linera_views::{
     bucket_queue_view::BucketQueueView,
     context::Context,
     register_view::RegisterView,
-    views::{ClonableView, View, ViewError},
+    views::{ClonableView, View},
+    ViewError,
 };
 
 #[cfg(test)]

linera-chain/src/outbox.rs

@@ -12,7 +12,8 @@ use linera_views::{
     context::Context,
     map_view::MapView,
     register_view::RegisterView,
-    views::{ClonableView, View, ViewError},
+    views::{ClonableView, View},
+    ViewError,
 };
 
 use crate::ChainError;

linera-chain/src/pending_blobs.rs

@@ -32,7 +32,7 @@ use linera_execution::{
 use linera_views::{
     context::{Context as _, MemoryContext, ViewContext},
     memory::MemoryStore,
-    views::{View, ViewError},
+    views::View,
 };
 use test_case::test_case;
 
@@ -43,13 +43,7 @@ use crate::{
     ChainError, ChainExecutionContext, ChainStateView,
 };
 
-impl ChainStateView<MemoryContext<TestExecutionRuntimeContext>>
-where
-    MemoryContext<TestExecutionRuntimeContext>:
-        linera_views::context::Context + Clone + Send + Sync + 'static,
-    ViewError:
-        From<<MemoryContext<TestExecutionRuntimeContext> as linera_views::context::Context>::Error>,
-{
+impl ChainStateView<MemoryContext<TestExecutionRuntimeContext>> {
     pub async fn new(chain_id: ChainId) -> Self {
         let exec_runtime_context =
             TestExecutionRuntimeContext::new(chain_id, ExecutionRuntimeConfig::default());

linera-chain/src/unit_tests/chain_tests.rs

@@ -27,7 +27,7 @@ pub(crate) enum Inner {
     #[error("persistence error: {0}")]
     Persistence(#[source] Box<dyn std::error::Error + Send + Sync>),
     #[error("view error: {0}")]
-    View(#[from] linera_views::views::ViewError),
+    View(#[from] linera_views::ViewError),
     #[error("non-existent chain: {0:?}")]
     NonexistentChain(linera_base::identifiers::ChainId),
     #[error("no keypair found for chain: {0:?}")]

linera-client/src/error.rs

@@ -27,7 +27,7 @@ use linera_chain::{
 };
 use linera_execution::{ExecutionStateView, Query, QueryOutcome, ServiceRuntimeEndpoint};
 use linera_storage::{Clock as _, Storage};
-use linera_views::views::{ClonableView, ViewError};
+use linera_views::{views::ClonableView, ViewError};
 use tokio::sync::{oneshot, OwnedRwLockReadGuard, RwLock};
 
 #[cfg(test)]

linera-core/src/chain_worker/state/mod.rs

@@ -60,7 +60,7 @@ use linera_execution::{
     ExecutionError, Operation, Query, QueryOutcome, QueryResponse, SystemQuery, SystemResponse,
 };
 use linera_storage::{Clock as _, Storage as _};
-use linera_views::views::ViewError;
+use linera_views::ViewError;
 use rand::prelude::SliceRandom as _;
 use serde::{Deserialize, Serialize};
 use thiserror::Error;