feat: read the full specialisation schema from bootspec

This fixes #147 by changing
the type of specialisations from `Generation` to `BootJson`.
This means that we capture the full recursive JSON schema for specialisations,
including extensions, while the previous type threw this information away.

This allows for instance to set specific sort keys for specialisations.
Such sort keys are allowed by the bootspec specification, but are
currently not retained when parsing a bootspec document.

Author: r-vdp

bootspec/rfc0125_spec.json

@@ -20,6 +20,9 @@
   },
   "org.nixos.specialisation.v1": {
     "<name>": {
+      "org.nix-community.test": {
+        "foo": "bar"
+      },
       "org.nixos.bootspec.v1": {
         "system": "x86_64-linux",
         "init": "/nix/store/xxx-nixos-system-xxx/init",

bootspec/src/generation.rs

@@ -88,6 +88,22 @@ mod tests {
             .map(ToOwned::to_owned)
             .collect::<Vec<_>>();
         assert!(keys.contains(&SpecialisationName(String::from("<name>"))));
+
+        assert_eq!(
+            from_json
+                .specialisations
+                .get(&SpecialisationName("<name>".into()))
+                .unwrap()
+                .extensions
+                .get("org.nix-community.test")
+                .unwrap()
+                .as_object()
+                .unwrap()
+                .get("foo")
+                .unwrap()
+                .as_str(),
+            Some("bar")
+        )
     }
 
     #[test]

bootspec/src/v1.rs

@@ -6,7 +6,7 @@ use std::path::{Path, PathBuf};
 use serde::{Deserialize, Serialize};
 
 use crate::error::{BootspecError, SynthesizeError};
-use crate::{Result, SpecialisationName, SystemConfigurationRoot};
+use crate::{BootJson, Result, SpecialisationName, SystemConfigurationRoot};
 
 /// The V1 bootspec schema version.
 pub const SCHEMA_VERSION: u64 = 1;
@@ -48,7 +48,7 @@ impl GenerationV1 {
 
                 specialisations.insert(
                     SpecialisationName(name.to_string()),
-                    Self::synthesize(&toplevel)?,
+                    BootJson::synthesize_version(&toplevel, SCHEMA_VERSION)?,
                 );
             }
         }
@@ -63,7 +63,7 @@ impl GenerationV1 {
 /// A mapping of V1 bootspec specialisations.
 ///
 /// This structure represents the contents of the `org.nixos.specialisations.v1` key.
-pub type SpecialisationsV1 = HashMap<SpecialisationName, GenerationV1>;
+pub type SpecialisationsV1 = HashMap<SpecialisationName, BootJson>;
 
 /// A V1 bootspec toplevel.
 ///