Add a "check-config" command to validate config files & tests for it

src/cli.rs

@@ -12,6 +12,7 @@ use crate::{
     error, observability,
 };
 
+mod check_config;
 mod serve;
 
 /// Command line arguments
@@ -29,6 +30,18 @@ pub(crate) struct Args {
 pub(crate) enum Command {
     /// Run the server.
     Serve(ServeArgs),
+
+    /// Check the configuration file for syntax and semantic errors.
+    CheckConfig(CheckConfigArgs),
+}
+
+#[derive(clap::Args)]
+pub(crate) struct CheckConfigArgs {
+    #[clap(flatten)]
+    config: ConfigArg,
+
+    #[clap(flatten)]
+    observability: ObservabilityArgs,
 }
 
 /// Wrapper for the `--config` arg.
@@ -83,6 +96,9 @@ impl Args {
 
         match self.command {
             Command::Serve(args) => serve::run(args).await?,
+            Command::CheckConfig(args) => {
+                check_config::run(args.config).await?;
+            }
         }
         Ok(())
     }
@@ -93,6 +109,10 @@ impl Command {
         // All subcommands other than `serve` should return `Some`. Keep these
         // match arms sorted by the enum variant name.
         match self {
+            Command::CheckConfig(args) => Some((
+                args.observability.log_format,
+                args.observability.log_filter.clone(),
+            )),
             Command::Serve(_) => None,
         }
     }