improve configuration loading mechanism

src/config.rs

@@ -5,11 +5,12 @@ use crate::extractors::ExtractorDeclaration;
 use crate::generators::GeneratorDeclaration;
 use crate::phases::PhasesConfiguration;
 use crate::utils;
-use anyhow::Context;
 use anyhow::Result;
+use anyhow::{Context, bail};
 use serde::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::ops::Deref;
+use toml::Value;
 use uefi::proto::device_path::LoadedImageDevicePath;
 
 #[derive(Serialize, Deserialize, Default, Clone)]
@@ -36,7 +37,7 @@ pub fn latest_version() -> u32 {
     1
 }
 
-pub fn load() -> Result<RootConfiguration> {
+fn load_raw_config() -> Result<Vec<u8>> {
     let current_image_device_path_protocol =
         uefi::boot::open_protocol_exclusive::<LoadedImageDevicePath>(uefi::boot::image_handle())
             .context("unable to get loaded image device path")?;
@@ -44,7 +45,28 @@ pub fn load() -> Result<RootConfiguration> {
 
     let content = utils::read_file_contents(&path, "sprout.toml")
         .context("unable to read sprout.toml file")?;
-    let config: RootConfiguration =
-        toml::from_slice(&content).context("unable to parse sprout.toml file")?;
+    Ok(content)
+}
+
+pub fn load() -> Result<RootConfiguration> {
+    let content = load_raw_config()?;
+    let value: Value = toml::from_slice(&content).context("unable to parse sprout.toml file")?;
+
+    let version = value
+        .get("version")
+        .cloned()
+        .unwrap_or_else(|| Value::Integer(latest_version() as i64));
+
+    let version: u32 = version
+        .try_into()
+        .context("unable to get configuration version")?;
+
+    if version != latest_version() {
+        bail!("unsupported configuration version: {}", version);
+    }
+
+    let config: RootConfiguration = value
+        .try_into()
+        .context("unable to parse sprout.toml file")?;
     Ok(config)
 }