Allow loading multiple configuration files

crates/cli/src/main.rs

@@ -23,6 +23,7 @@ use std::path::PathBuf;
 use anyhow::Context;
 use clap::Clap;
 use mas_config::ConfigurationSection;
+use tracing::trace;
 use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt, EnvFilter, Registry};
 
 use self::{
@@ -57,8 +58,14 @@ enum Subcommand {
 #[derive(Clap, Debug)]
 struct RootCommand {
     /// Path to the configuration file
-    #[clap(short, long, global = true, default_value = "config.yaml")]
+    #[clap(
-    config: PathBuf,
+        short,
+        long,
+        global = true,
+        default_value = "config.yaml",
+        multiple_occurrences(true)
+    )]
+    config: Vec<PathBuf>,
 
     #[clap(subcommand)]
     subcommand: Option<Subcommand>,
@@ -78,7 +85,7 @@ impl RootCommand {
     }
 
     fn load_config<'de, T: ConfigurationSection<'de>>(&self) -> anyhow::Result<T> {
-        T::load_from_file(&self.config).context("could not load configuration")
+        T::load_from_files(&self.config).context("could not load configuration")
     }
 }
 
@@ -105,5 +112,6 @@ async fn main() -> anyhow::Result<()> {
     let opts = RootCommand::parse();
 
     // And run the command
+    trace!(?opts, "Running command");
     opts.run().await
 }

crates/config/src/util.rs

@@ -56,15 +56,25 @@ pub trait ConfigurationSection<'a>: Sized + Deserialize<'a> + Serialize {
             .context("could not load configuration")
     }
 
+    /// Load configuration from a list of files and environment variables.
+    fn load_from_files<P>(paths: &[P]) -> Result<Self, FigmentError>
+    where
+        P: AsRef<Path>,
+    {
+        let base = Figment::new().merge(Env::prefixed("MAS_").split("_"));
+
+        paths
+            .iter()
+            .fold(base, |f, path| f.merge(Yaml::file(path)))
+            .extract_inner(Self::path())
+    }
+
     /// Load configuration from a file and environment variables.
     fn load_from_file<P>(path: P) -> Result<Self, FigmentError>
     where
         P: AsRef<Path>,
     {
-        Figment::new()
+        Self::load_from_files(&[path])
-            .merge(Env::prefixed("MAS_").split("_"))
-            .merge(Yaml::file(path))
-            .extract_inner(Self::path())
     }
 
     /// Generate config used in unit tests