split out separate error type for serve command

src/cli.rs

@@ -60,7 +60,8 @@ pub(crate) struct ServeArgs {
 impl Args {
     pub(crate) async fn run(self) -> Result<(), error::Main> {
         match self.command {
-            Command::Serve(args) => serve::run(args).await,
+            Command::Serve(args) => serve::run(args).await?,
         }
+        Ok(())
     }
 }

src/cli/serve.rs

@@ -44,8 +44,8 @@ use crate::{
     utils::error::{Error, Result},
 };
 
-pub(crate) async fn run(args: ServeArgs) -> Result<(), error::Main> {
+pub(crate) async fn run(args: ServeArgs) -> Result<(), error::ServeCommand> {
-    use error::Main as Error;
+    use error::ServeCommand as Error;
 
     let config = config::load(args.config.config.as_ref()).await?;
 

src/error.rs

@@ -40,6 +40,16 @@ impl fmt::Display for DisplayWithSources<'_> {
 #[allow(missing_docs)]
 #[derive(Error, Debug)]
 pub(crate) enum Main {
+    #[error(transparent)]
+    ServeCommand(#[from] ServeCommand),
+}
+
+/// Errors returned from the `serve` CLI subcommand.
+// Missing docs are allowed here since that kind of information should be
+// encoded in the error messages themselves anyway.
+#[allow(missing_docs)]
+#[derive(Error, Debug)]
+pub(crate) enum ServeCommand {
     #[error("failed to load configuration")]
     Config(#[from] Config),