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/settings/src/keymap_file.rs

@@ -1,4 +1,4 @@
-use anyhow::{Result, anyhow};
+use anyhow::Result;
 use collections::{BTreeMap, HashMap, IndexMap};
 use fs::Fs;
 use gpui::{
@@ -154,12 +154,12 @@ impl KeymapFile {
     pub fn load_asset(asset_path: &str, cx: &App) -> anyhow::Result<Vec<KeyBinding>> {
         match Self::load(asset_str::<SettingsAssets>(asset_path).as_ref(), cx) {
             KeymapFileLoadResult::Success { key_bindings } => Ok(key_bindings),
-            KeymapFileLoadResult::SomeFailedToLoad { error_message, .. } => Err(anyhow!(
-                "Error loading built-in keymap \"{asset_path}\": {error_message}",
-            )),
-            KeymapFileLoadResult::JsonParseFailure { error } => Err(anyhow!(
-                "JSON parse error in built-in keymap \"{asset_path}\": {error}"
-            )),
+            KeymapFileLoadResult::SomeFailedToLoad { error_message, .. } => {
+                anyhow::bail!("Error loading built-in keymap \"{asset_path}\": {error_message}",)
+            }
+            KeymapFileLoadResult::JsonParseFailure { error } => {
+                anyhow::bail!("JSON parse error in built-in keymap \"{asset_path}\": {error}")
+            }
         }
     }
 
@@ -173,14 +173,14 @@ impl KeymapFile {
                 key_bindings,
                 error_message,
                 ..
-            } if key_bindings.is_empty() => Err(anyhow!(
-                "Error loading built-in keymap \"{asset_path}\": {error_message}",
-            )),
+            } if key_bindings.is_empty() => {
+                anyhow::bail!("Error loading built-in keymap \"{asset_path}\": {error_message}",)
+            }
             KeymapFileLoadResult::Success { key_bindings, .. }
             | KeymapFileLoadResult::SomeFailedToLoad { key_bindings, .. } => Ok(key_bindings),
-            KeymapFileLoadResult::JsonParseFailure { error } => Err(anyhow!(
-                "JSON parse error in built-in keymap \"{asset_path}\": {error}"
-            )),
+            KeymapFileLoadResult::JsonParseFailure { error } => {
+                anyhow::bail!("JSON parse error in built-in keymap \"{asset_path}\": {error}")
+            }
         }
     }
 

crates/settings/src/settings_store.rs

@@ -1,4 +1,4 @@
-use anyhow::{Context as _, Result, anyhow};
+use anyhow::{Context as _, Result};
 use collections::{BTreeMap, HashMap, btree_map, hash_map};
 use ec4rs::{ConfigParser, PropertiesSource, Section};
 use fs::Fs;
@@ -635,13 +635,10 @@ impl SettingsStore {
         cx: &mut App,
     ) -> Result<()> {
         let settings: Value = parse_json_with_comments(default_settings_content)?;
-        if settings.is_object() {
-            self.raw_default_settings = settings;
-            self.recompute_values(None, cx)?;
-            Ok(())
-        } else {
-            Err(anyhow!("settings must be an object"))
-        }
+        anyhow::ensure!(settings.is_object(), "settings must be an object");
+        self.raw_default_settings = settings;
+        self.recompute_values(None, cx)?;
+        Ok(())
     }
 
     /// Sets the user settings via a JSON string.