settings: propagate configuration error of commit and operation parameters

Note that infallible version of whoami::username() would return "Unknown" on
error. I just made it error out, but it's also an option to fall back to an
empty string.

Author: yuja

CHANGELOG.md

@@ -18,8 +18,10 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 * The following configuration variables are now parsed strictly:
   `colors.<labels>`, `git.abandon-unreachable-commits`,
   `git.auto-local-bookmark`, `git.push-bookmark-prefix`, `revsets.log`,
-  `revsets.short-prefixes` `signing.backend`, `ui.allow-init-native`,
-  `ui.color`, `ui.default-description`, `ui.progress-indicator`, `ui.quiet`
+  `revsets.short-prefixes` `signing.backend`, `operation.hostname`,
+  `operation.username`, `ui.allow-init-native`, `ui.color`,
+  `ui.default-description`, `ui.progress-indicator`, `ui.quiet`, `user.email`,
+  `user.name`
 
 * `jj config list` now prints inline tables `{ key = value, .. }` literally.
   Inner items of inline tables are no longer merged across configuration files.

lib/src/settings.rs

@@ -146,20 +146,36 @@ fn to_timestamp(value: ConfigValue) -> Result<Timestamp, Box<dyn std::error::Err
 
 impl UserSettings {
     pub fn from_config(config: StackedConfig) -> Result<Self, ConfigGetError> {
-        let user_name = config.get("user.name").unwrap_or_default();
-        let user_email = config.get("user.email").unwrap_or_default();
+        let user_name = config.get("user.name").optional()?.unwrap_or_default();
+        let user_email = config.get("user.email").optional()?.unwrap_or_default();
         let commit_timestamp = config
             .get_value_with("debug.commit-timestamp", to_timestamp)
             .optional()?;
         let operation_timestamp = config
             .get_value_with("debug.operation-timestamp", to_timestamp)
             .optional()?;
+        // whoami::fallible::*() failure isn't a ConfigGetError, but user would
+        // have to set the corresponding config keys if these parameter can't be
+        // obtained from the system. Instead of handling environment data here,
+        // it might be better to load them by CLI and insert as a config layer.
         let operation_hostname = config
             .get("operation.hostname")
-            .unwrap_or_else(|_| whoami::fallible::hostname().expect("valid hostname"));
+            .optional()?
+            .map_or_else(whoami::fallible::hostname, Ok)
+            .map_err(|err| ConfigGetError::Type {
+                name: "operation.hostname".to_owned(),
+                error: err.into(),
+                source_path: None,
+            })?;
         let operation_username = config
             .get("operation.username")
-            .unwrap_or_else(|_| whoami::username());
+            .optional()?
+            .map_or_else(whoami::fallible::username, Ok)
+            .map_err(|err| ConfigGetError::Type {
+                name: "operation.username".to_owned(),
+                error: err.into(),
+                source_path: None,
+            })?;
         let rng_seed = config.get::<u64>("debug.randomness-seed").optional()?;
         Ok(UserSettings {
             config,