Load the configuration from a common Figment instance

This should avoid loading the same files multiple times.
It should also make it easier to do post-processing on the
configuration, like validation.

This does deprecate one undocumented feature: the ability to override
some fields during the configuration generation using environment
variables.

crates/config/Cargo.toml

@@ -21,7 +21,7 @@ anyhow.workspace = true
 
 camino = { workspace = true, features = ["serde1"] }
 chrono.workspace = true
-figment = { version = "0.10.15", features = ["env", "yaml", "test"] }
+figment.workspace = true
 ipnetwork = { version = "0.20.0", features = ["serde", "schemars"] }
 schemars.workspace = true
 ulid.workspace = true

crates/config/src/sections/clients.rs

@@ -201,7 +201,10 @@ impl ConfigurationSection for ClientsConfig {
 mod tests {
     use std::str::FromStr;
 
-    use figment::Jail;
+    use figment::{
+        providers::{Format, Yaml},
+        Figment, Jail,
+    };
 
     use super::*;
 
@@ -249,7 +252,9 @@ mod tests {
                 "#,
             )?;
 
-            let config = ClientsConfig::load_from_file("config.yaml")?;
+            let config = Figment::new()
+                .merge(Yaml::file("config.yaml"))
+                .extract_inner::<ClientsConfig>("clients")?;
 
             assert_eq!(config.0.len(), 5);
 

crates/config/src/sections/database.rs

@@ -164,7 +164,10 @@ impl ConfigurationSection for DatabaseConfig {
 
 #[cfg(test)]
 mod tests {
-    use figment::Jail;
+    use figment::{
+        providers::{Format, Yaml},
+        Figment, Jail,
+    };
 
     use super::*;
 
@@ -179,7 +182,9 @@ mod tests {
                 ",
             )?;
 
-            let config = DatabaseConfig::load_from_file("config.yaml")?;
+            let config = Figment::new()
+                .merge(Yaml::file("config.yaml"))
+                .extract_inner::<DatabaseConfig>("database")?;
 
             assert_eq!(
                 config.options,

crates/config/src/sections/matrix.rs

@@ -76,7 +76,10 @@ impl ConfigurationSection for MatrixConfig {
 
 #[cfg(test)]
 mod tests {
-    use figment::Jail;
+    use figment::{
+        providers::{Format, Yaml},
+        Figment, Jail,
+    };
 
     use super::*;
 
@@ -92,10 +95,12 @@ mod tests {
                 ",
             )?;
 
-            let config = MatrixConfig::load_from_file("config.yaml")?;
+            let config = Figment::new()
+                .merge(Yaml::file("config.yaml"))
+                .extract_inner::<MatrixConfig>("matrix")?;
 
-            assert_eq!(config.homeserver, "matrix.org".to_owned());
-            assert_eq!(config.secret, "test".to_owned());
+            assert_eq!(&config.homeserver, "matrix.org");
+            assert_eq!(&config.secret, "test");
 
             Ok(())
         });

crates/config/src/util.rs

@@ -12,14 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use anyhow::Context;
 use async_trait::async_trait;
-use camino::Utf8Path;
-use figment::{
-    error::Error as FigmentError,
-    providers::{Env, Format, Serialized, Yaml},
-    Figment, Profile,
-};
+use figment::{error::Error as FigmentError, Figment};
 use rand::Rng;
 use serde::{de::DeserializeOwned, Serialize};
 
@@ -35,64 +29,13 @@ pub trait ConfigurationSection: Sized + DeserializeOwned + Serialize {
     where
         R: Rng + Send;
 
-    /// Generate a sample configuration and override it with environment
-    /// variables.
-    ///
-    /// This is what backs the `config generate` subcommand, allowing to
-    /// programmatically generate a configuration file, e.g.
-    ///
-    /// ```sh
-    /// export MAS_OAUTH2_ISSUER=https://example.com/
-    /// export MAS_HTTP_ADDRESS=127.0.0.1:1234
-    /// matrix-authentication-service config generate
-    /// ```
-    ///
-    /// # Errors
-    ///
-    /// Returns an error if the configuration could not be generated or if the
-    /// existing configuration could not be loaded
-    async fn load_and_generate<R>(rng: R) -> anyhow::Result<Self>
-    where
-        R: Rng + Send,
-    {
-        let base = Self::generate(rng)
-            .await
-            .context("could not generate configuration")?;
-
-        Figment::new()
-            .merge(Serialized::from(&base, Profile::Default))
-            .merge(Env::prefixed("MAS_").split("_"))
-            .extract_inner(Self::path())
-            .context("could not load configuration")
-    }
-
-    /// Load configuration from a list of files and environment variables.
+    /// Extract configuration from a Figment instance.
     ///
     /// # Errors
     ///
     /// Returns an error if the configuration could not be loaded
-    fn load_from_files<P>(paths: &[P]) -> Result<Self, FigmentError>
-    where
-        P: AsRef<Utf8Path>,
-    {
-        let base = Figment::new().merge(Env::prefixed("MAS_").split("_"));
-
-        paths
-            .iter()
-            .fold(base, |f, path| f.merge(Yaml::file(path.as_ref())))
-            .extract_inner(Self::path())
-    }
-
-    /// Load configuration from a file and environment variables.
-    ///
-    /// # Errors
-    ///
-    /// Returns an error if the configuration could not be loaded
-    fn load_from_file<P>(path: P) -> Result<Self, FigmentError>
-    where
-        P: AsRef<Utf8Path>,
-    {
-        Self::load_from_files(&[path])
+    fn extract(figment: &Figment) -> Result<Self, FigmentError> {
+        figment.extract_inner(Self::path())
     }
 
     /// Generate config used in unit tests