Use anyhow more idiomatically (#31052)

https://github.com/zed-industries/zed/issues/30972 brought up another
case where our context is not enough to track the actual source of the
issue: we get a general top-level error without inner error.

The reason for this was `.ok_or_else(|| anyhow!("failed to read HEAD
SHA"))?; ` on the top level.

The PR finally reworks the way we use anyhow to reduce such issues (or
at least make it simpler to bubble them up later in a fix).
On top of that, uses a few more anyhow methods for better readability.

* `.ok_or_else(|| anyhow!("..."))`, `map_err` and other similar error
conversion/option reporting cases are replaced with `context` and
`with_context` calls
* in addition to that, various `anyhow!("failed to do ...")` are
stripped with `.context("Doing ...")` messages instead to remove the
parasitic `failed to` text
* `anyhow::ensure!` is used instead of `if ... { return Err(...); }`
calls
* `anyhow::bail!` is used instead of `return Err(anyhow!(...));`

Release Notes:

- N/A

crates/assistant_context_editor/src/context.rs

@@ -1,7 +1,7 @@
 #[cfg(test)]
 mod context_tests;
 
-use anyhow::{Context as _, Result, anyhow, bail};
+use anyhow::{Context as _, Result, bail};
 use assistant_settings::AssistantSettings;
 use assistant_slash_command::{
     SlashCommandContent, SlashCommandEvent, SlashCommandLine, SlashCommandOutputSection,
@@ -3011,7 +3011,7 @@ impl SavedContext {
         let saved_context_json = serde_json::from_str::<serde_json::Value>(json)?;
         match saved_context_json
             .get("version")
-            .ok_or_else(|| anyhow!("version not found"))?
+            .context("version not found")?
         {
             serde_json::Value::String(version) => match version.as_str() {
                 SavedContext::VERSION => {
@@ -3032,9 +3032,9 @@ impl SavedContext {
                         serde_json::from_value::<SavedContextV0_1_0>(saved_context_json)?;
                     Ok(saved_context.upgrade())
                 }
-                _ => Err(anyhow!("unrecognized saved context version: {}", version)),
+                _ => anyhow::bail!("unrecognized saved context version: {version:?}"),
             },
-            _ => Err(anyhow!("version not found on saved context")),
+            _ => anyhow::bail!("version not found on saved context"),
         }
     }
 

crates/assistant_context_editor/src/context_store.rs

@@ -2,7 +2,7 @@ use crate::{
     AssistantContext, ContextEvent, ContextId, ContextOperation, ContextVersion, SavedContext,
     SavedContextMetadata,
 };
-use anyhow::{Context as _, Result, anyhow};
+use anyhow::{Context as _, Result};
 use assistant_slash_command::{SlashCommandId, SlashCommandWorkingSet};
 use client::{Client, TypedEnvelope, proto, telemetry::Telemetry};
 use clock::ReplicaId;
@@ -164,16 +164,18 @@ impl ContextStore {
     ) -> Result<proto::OpenContextResponse> {
         let context_id = ContextId::from_proto(envelope.payload.context_id);
         let operations = this.update(&mut cx, |this, cx| {
-            if this.project.read(cx).is_via_collab() {
-                return Err(anyhow!("only the host contexts can be opened"));
-            }
+            anyhow::ensure!(
+                !this.project.read(cx).is_via_collab(),
+                "only the host contexts can be opened"
+            );
 
             let context = this
                 .loaded_context_for_id(&context_id, cx)
                 .context("context not found")?;
-            if context.read(cx).replica_id() != ReplicaId::default() {
-                return Err(anyhow!("context must be opened via the host"));
-            }
+            anyhow::ensure!(
+                context.read(cx).replica_id() == ReplicaId::default(),
+                "context must be opened via the host"
+            );
 
             anyhow::Ok(
                 context
@@ -193,9 +195,10 @@ impl ContextStore {
         mut cx: AsyncApp,
     ) -> Result<proto::CreateContextResponse> {
         let (context_id, operations) = this.update(&mut cx, |this, cx| {
-            if this.project.read(cx).is_via_collab() {
-                return Err(anyhow!("can only create contexts as the host"));
-            }
+            anyhow::ensure!(
+                !this.project.read(cx).is_via_collab(),
+                "can only create contexts as the host"
+            );
 
             let context = this.create(cx);
             let context_id = context.read(cx).id().clone();
@@ -237,9 +240,10 @@ impl ContextStore {
         mut cx: AsyncApp,
     ) -> Result<proto::SynchronizeContextsResponse> {
         this.update(&mut cx, |this, cx| {
-            if this.project.read(cx).is_via_collab() {
-                return Err(anyhow!("only the host can synchronize contexts"));
-            }
+            anyhow::ensure!(
+                !this.project.read(cx).is_via_collab(),
+                "only the host can synchronize contexts"
+            );
 
             let mut local_versions = Vec::new();
             for remote_version_proto in envelope.payload.contexts {
@@ -370,7 +374,7 @@ impl ContextStore {
     ) -> Task<Result<Entity<AssistantContext>>> {
         let project = self.project.read(cx);
         let Some(project_id) = project.remote_id() else {
-            return Task::ready(Err(anyhow!("project was not remote")));
+            return Task::ready(Err(anyhow::anyhow!("project was not remote")));
         };
 
         let replica_id = project.replica_id();
@@ -533,7 +537,7 @@ impl ContextStore {
     ) -> Task<Result<Entity<AssistantContext>>> {
         let project = self.project.read(cx);
         let Some(project_id) = project.remote_id() else {
-            return Task::ready(Err(anyhow!("project was not remote")));
+            return Task::ready(Err(anyhow::anyhow!("project was not remote")));
         };
 
         if let Some(context) = self.loaded_context_for_id(&context_id, cx) {